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Case Study Questions Class 9 Science Matter in our Surroundings

Case study questions class 9 science chapter 1 matter in our surroundings.

CBSE Class 9 Case Study Questions Science Matter in our Surroundings. Important Case Study Questions for Class 9 Exam. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Matter in our Surroundings.

At Case Study Questions there will given a Paragraph. In where some Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks or 4 marks.

CBSE Case Study Questions Class 9 Science – Matter in our Surroundings

Case study 1:.

1.) A matter is anything that has mass and occupies space. Pen, paper, clips, sand, air, ice, etc. are different forms of matter. Every matter is made up of small particles. These particles are so tiny that they can’t be seen with naked eyes. Let’s see about the different characteristics of particles of matter.

• All matter is made up of very small particles.
• .Particles of matter has spaces between them.
• Particles of matter are continuously moving.
• Particles of matter attract each other.

Answer the following questions by referring above paragraph.

i.) Which of following is not matter?

c.) smell of perfume

d.) None of these

ii.) Thoughts coming in our mind are example of matter. True or false

c.) None of these

iii.) Which of the following is true about particles of matter?

a.) Particles of matter has spaces between them

b.) Particles of matter are continuously moving

c.) Particles of matter attract each other

d.) All of these

iv.) Give 5 examples of matter in our surroundings

v.) Enlist all properties of particles of matter

Answer key-1

iv.) pen, pencil, notebook, ice and water

v.) Different characteristics of particles of matter are

Case Study 2:

2.) There are three states of matter – solid, liquid and gas.

Solids have a definite shape, distinct boundaries and fixed volumes, that is, have negligible compressibility. Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.

Liquids have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

Gas as has indefinite shape, no fixed volume. Gas gets the shape and volume of container.

Gas has very low density hence are light. Gas can flow easily and hence are called fluid.

i.) Which of the following state of matter takes shape of container in which it is filled?

d.) Both b and c

ii.) Distance between particles of matter least in

iii.) Compressibility is least in case of

iv.) Give properties of solids.

v.) Give properties of Gases.

Answer key-2

iv.) properties of solid are given below

• Solid has fixed volume.
• Solid has fixed shape.
• Solid has high density.
• Solids are heavy.
• Solid does not flow.

v.) Properties of gases are

• Gas has indefinite shape
• Gas has no fixed volume.
• Gas gets the shape and volume of container.
• Gas fills the container completely.
• Gas has very low density.
• Because of low density gas are light.
• Gas can flow easily and hence are called fluid.

Case Study 3:

3.) What happens inside the matter during change of state? On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase in kinetic energy, the

Particles start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage is reached when the solid melts and is converted to a liquid. The minimum temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

The temperature of the system does not change after the melting point is reached, till all the ice melts. This happens even though we continue to heat the beaker, that is, we continue to supply heat. This heat gets used up in changing the state by overcoming the forces of attraction between the particles. The amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point is known as the latent heat of fusion. So, particles in water at 0 0 C (273 K) have more energy as compared to particles in ice at the same temperature.

The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point. Boiling is a bulk phenomenon. Particles from the bulk of the liquid gain enough energy to change into the vapour state. A change of state directly from solid to gas without changing into liquid state is called sublimation and the direct change of gas to solid without changing into liquid is called deposition.

i.) A change of state directly from solid to gas without changing into liquid state is called

a.) Sublimation

b.) Deposition

c.) Boiling point

ii.) The direct change of gas to solid without changing into liquid is called

iii.) The energy supplied by heat to solid is used to overcome the forces of attraction between the particles. True or false

iv.) Define melting point and boiling point

v.) Define latent heat of fusion

Answer key-3

iv.) The minimum temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point.

v.) The amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.

Case Study 4:

4 .) Do we always need to heat or change pressure for changing the state of matter? Can you quote some examples from everyday life where change of state from liquid to vapour takes place without the liquid reaching the boiling point? In the case of liquids, a small fraction of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction of other particles and gets converted into vapour. This phenomenon of change of a liquid into vapors at any temperature below its boiling point is called evaporation.

i.) Evaporation of liquid takes place at

a.) Boiling point

b.) Above boiling point

c.) Below boiling point

ii.) Evaporation takes place at surface of liquid because

a.) They are heavy as compare to other particles

b.) They have sufficient kinetic energy to break the force

c.) They are light weight as compare to other particles

iii.) During evaporation particles of liquid change into vapour

a.) From the surface

b.) From the bottom

c.) From all over the liquid

iv.) Define evaporation.

v.) Explain process of evaporation

Answer key-4

iv.) The phenomenon of change of a liquid into vapors at any temperature below its boiling point is called evaporation.

v.) In the case of liquids, a small fraction of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction of other particles and gets converted into vapour. This phenomenon of change of a liquid into vapors at any temperature below its boiling point is called evaporation.

Case Study 5:

5.) You must have observed that the rate of evaporation increases with–

• an increase of surface area:
• We know that evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation increases. For example, while putting clothes for drying up we spread them out.
• an increase of temperature:

With the increase of temperature, more number of particles get enough kinetic energy to go into the vapour state.

In an open vessel, the liquid keeps on evaporating. The particles of liquid absorb energy from the surrounding to regain the energy lost during evaporation. This absorption of energy from the surroundings makes the surroundings cold. What happens when you pour some acetone (nail polish remover) on your palm? The particles gain energy from your palm or surroundings and evaporate causing the palm to feel cool. After a hot sunny day, people sprinkle water on the roof or open ground because the large latent heat of vaporization of water helps to cool the hot surface.

i.) Evaporation is surface phenomenon. True or false

ii.) As temperature increases the rate of evaporation is

a.) increases

b.) decreases

c.) remains constant

iii.) The rate of evaporation increases with

a.) Increase in wind speed

b.) Decrease in wind speed

c.) Does not have any effect from wind speed

iv.) What happens when you pour some acetone (nail polish remover) on your palm?

v.) We are able to sip hot tea from saucer than from cup. Why?

Answer key-5

iv.) The particles gain energy from your palm or surroundings and evaporate causing the palm to feel cool.

v.) We are able to sip hot tea from saucer than from cup. This is because saucer has large surface area, due to large surface area as compare to cut area tea evaporates at faster rate.

Thank you It helped me a lot

Why smell of Perfume is not a matter?

Because there is no particle

Because their are perfume particles suspended in air

These all case study questions are really helpful . Thanks

This is my first I was so nervous but these questions help me alot thank you

Smell of perfume is a matter because it have gas particles means perfume particles

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Class 9 Science Case Study Questions Chapter 1 Matter in our Surroundings

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Case study Questions in Class 9 Science Chapter 1 are very important to solve for your exam. Class 9 Science Chapter 1 Case Study Questions have been prepared for the latest exam pattern. You can check your knowledge by solving Class 9 Science Case Study Questions  Chapter 1 Matter in our Surroundings

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In CBSE Class 9 Science Paper, Students will have to answer some questions based on Assertion and Reason. There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.

Matter in our Surroundings Case Study Questions With Answers

Here, we have provided case-based/passage-based questions for Class 9 Science  Chapter 1 Matter in our Surroundings

Case Study/Passage-Based Questions

Case Study 1: There are three states of matter – solid, liquid, and gas.

Solids  have a definite shape, distinct boundaries, and fixed volumes, that is, have negligible compressibility. Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.

Liquids  have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

Gas  has an indefinite shape and no fixed volume. Gas gets the shape and volume of the container.Gas has a very low density and hence is light. Gas can flow easily and hence is called fluid.

i.) Which of the following state of matter takes the shape of the container in which it is filled?

d.) Both b and c

Answer: d.) Both b and c

ii.) Distance between particles of matter least in

d.) None of these

Answer: a.) Solid

iii.) Compressibility is least in case of

Case Study 2: Matter is anything that occupies space and has mass. It exists in various forms, such as solid, liquid, and gas. The physical properties of matter, such as shape, size, and state, can be observed and measured. The particles that makeup matter are constantly in motion, and their motion determines the state of matter. In a solid, the particles are tightly packed and have a fixed shape and volume. In a liquid, the particles are close together but can move past each other, giving the substance a fixed volume but no fixed shape. In a gas, the particles are far apart and move freely, allowing the substance to occupy any volume and shape. Matter can undergo changes in its state through the processes of evaporation, condensation, melting, and freezing. Understanding the properties and behavior of matter is essential for studying various scientific phenomena and practical applications in our daily lives.

What is matter? a) Anything that occupies space and has mass b) Anything that is visible to the naked eye c) Anything that is in a solid state d) Anything that is in a gaseous state Answer: a) Anything that occupies space and has mass

What determines the state of matter? a) Physical properties b) Chemical properties c) The motion of particles d) The color of the substance Answer: c) The motion of particles

How are particles arranged in a solid? a) Far apart and move freely b) Close together but can move past each other c) Tightly packed and have a fixed shape d) Tightly packed but have no fixed shape Answer: c) Tightly packed and have a fixed shape

What is the behavior of particles in a gas? a) They are far apart and move freely b) They are close together but can move past each other c) They are tightly packed and have a fixed shape d) They are tightly packed but have no fixed shape Answer: a) They are far apart and move freely

What processes can matter undergo to change its state? a) Evaporation, condensation, melting, and freezing b) Dissolution, combustion, sublimation, and oxidation c) Fermentation, photosynthesis, respiration, and digestion d) Oxidation, reduction, precipitation, and ionization Answer: a) Evaporation, condensation, melting, and freezing

Hope the information shed above regarding Case Study and Passage Based Questions for Class 9 Science Chapter 1 Matter in our Surroundings with Answers Pdf free download has been useful to an extent. If you have any other queries about CBSE Class 9 Science Matter in our Surroundings Case Study and Passage Based Questions with Answers, feel free to comment below so that we can revert back to us at the earliest possible By Team Study Rate

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Case Study Questions of Chapter 1 Matter in our Surroundings PDF Download

Case study Questions on Class 9 Science Chapter 1 are very important to solve for your exam. Class 9 Science Chapter 1 Case Study Questions have been prepared for the latest exam pattern. You can check your knowledge by solving case study-based questions for Class 9 Science Chapter 1 Matter in our Surroundings

In CBSE Class 9 Science Paper, Students will have to answer some questions based on Assertion and Reason. There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.

Matter in our Surroundings Case Study Questions With answers

Here, we have provided case-based/passage-based questions for Class 9 Science  Chapter 1 Matter in our Surroundings

Case Study/Passage-Based Questions

Question 1:

There are three states of matter – solid, liquid, and gas.

Solids  have a definite shape, distinct boundaries, and fixed volumes, that is, have negligible compressibility. Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.

Liquids  have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

Gas  has an indefinite shape and no fixed volume. Gas gets the shape and volume of the container.

Gas has very low density hence is light. Gas can flow easily and hence is called fluid.

i.) Which of the following state of matter takes shape of the container in which it is filled?

d.) Both b and c

Answer: d.) Both b and c

ii.) Distance between particles of matter least in

d.) None of these

Answer: a.) Solid

iii.) Compressibility is least in case of

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Class 9th Science - Matter in Our Surroundings Case Study Questions and Answers 2022 - 2023

Class 9th Science - Matter in Our Surroundings Case Study Questions and Answers 2022 - 2023 Study Materials Sep-09 , 2022

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Matter in our surroundings case study questions with answer key.

Final Semester - June 2015

 Case Study 

(ii) Name the brown gas which could be in jar A.

(iii) Which is the colourless gas most likely to be present in jar B ?

(iv) When a gas jar full of air is placed upside down on a gas jar full of bromine vapours, the red-brown vapours of bromine from the lower jar go upward into the jar containing air. In this experiment : (a) air is heavier than bromine (b) both air and bromine have the same density (c) bromine is heavier than air (d) bromine cannot be heavier than air because it is going upwards against gravity (v) When a gas jar containing colourless air is kept upside down over a gas jar full of brown-coloured bromine vapour, then after some time, the brown colour of bromine vapour spreads into the upper gas jar making both the gas jars appear brown in colour. Which of the following conclusion obtained from these observations is incorrect ? (a) bromine vapour is made of tiny particles which are moving (b) air is made up of tiny particles which are moving (c) the particles of bromine are moving but those of air are not moving (d) even though bromine vapour is heavier than air, it can move up against gravity

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Unit 2: Matter in Our Surroundings

Matter and particles that make up matter..

• Characteristics of particles of matter (Opens a modal)
• Characteristics of particles of matter Get 4 of 5 questions to level up!

States of matter

• States of matter (Opens a modal)
• Effect of temp and pressure on state change (Opens a modal)
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• Evaporation and its cooling effects Get 5 of 7 questions to level up!

Class 9 Science Chapter 1 Case Based Questions - Matter in Our Surroundings

(I) Read the given passage and answer the questions that follows based on the passage and related studied concepts. Matter is anything that occupies space and has mass. Matter is classified into solid, liquid and gas. In solid state particles are closely packed and have very strong force of attraction, particles can only vibrate and rotate around fixed positions. In liquid state, particles are less closely packed and have strong force of attraction but less than solids, particles can move throughout the liquid. In Gaseous state, particles are far apart with weak force of attraction and are in state of constant random motion. Gases can be easily compressed where as solids and liquids are incompressible. Q1: An inflated balloon is placed in refrigerator, what will happen? (a)  Balloon will shrink and particles will move faster and become closer. (b) Balloon will expand and particles will move faster and become far apart. (c)  Balloon will shrink, particles will move slower and become close together. (d) Balloon will expand, particles will move slower and come closer therefore, volume of balloon will decrease. Ans: (c)  Kinetic energy will decrease, so particles will move slower, become closer and volume of balloon will decrease.

Q2: When solid changes into vapours, the process is called. (a) Evaporation (b) Boiling (c)  Sublimation (d)  Vapourisation Ans:  (c)

Q3: A substance melts at 5°C and boils at 150°C. What will be its physical state at room temperature?  Ans:  Liquid

Q4: Why do we feel more cold after taking bath with hot water? Ans:  It is because hot water evaporates faster than cold water and cause more cooling.

Q2: What does AB represent? Ans:  It represents a mixture of liquid and vapours at boiling point of liquid.

Q3: Why does temperature remain constant at boiling point? Ans: It is because heat of vaporization is used to overcome force of attraction between particles of liquid.

Q4: What does BC represent? Ans:  It represents vapour state and particles absorb heat and become more energetic. The tempera-ture of gas will rise.

(III) Read the following information and answer the questions based on information and related studied concepts Substance – 1. is brittle. Substance – 2. melts at 5°C and boils at 150°C. Substance – 3. has high melting point of 800°C. Substance – 4. has melting point –169°C and boiling point –104°C.

Q1:  What is physical state of substance – 4 at –150°C and –100°C? Ans:  Substance 4 is liquid at –150°C and gas at –100°C.

Q2: What is physical state of substance – 1 and 3 at room temperature? Ans:  Substance 1 and 3 are solids at room tempera-ture.

Q3: What is physical state of substance – 2 at 100°? Ans:  It will be in liquid state.

Q4: Out of substances – 1, 2, 3, 4 which one has strongest force of attraction? Ans:  Substance 3 has strongest forces of attraction.

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NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings

NCERT Solutions for Class 9 Science (chemistry) Chapter 1 Matter in Our Surroundings are given below. In these solutions, we have answered all the intext and exercise questions provided in NCERT class 9 science textbook. Class 9 NCERT Solutions Science Chapter 1 provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free from our app.

Class 9 Science Chapter 1 Textbook Questions and Answers

Intext Questions

Question 1:  Which of the following are matter? 

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume. 

Answer: Chair, air, almonds, and cold-drink are matters. 

Explanation: Things that occupy space and have some mass are called matter. Since chair, air, almonds and cold-drink occupy some space and have some mass, so these are matter.

Question 2: Give reasons for the following observation: 

The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close. 

Answer: The smell of hot sizzling food reaches severed meters away, as the particles of hot food have more kinetic energy and hence the rate of diffusion is more than the particles of cold food.

  Smell of anything comes because of gases emanating from the given thing. The smell reaches to us because of diffusion of gas. The rate of diffusion increases with increase in temperature. This happens because of higher kinetic energy due to higher temperature. That is why smell of hot sizzling food reaches to us from several feet. On the other hand, the kinetic energy of gases emanating from cold food is low because of lower temperature. Due to this, we need to move closer to a cold food to take its smell.

Question 3: A diver is able to cut through water in a swimming pool. Which property of matter does this observation show? 

Answer: A diver is able to cut through water in a swimming pool. This shows that the particles of water have intermolecular space and has less force of attraction.

 Question 4: What are the characteristics of particles of matter? 

Answer: The characteristics of particles of matter are:

• Particles of matter have spaces between them. 
• Particles of matter are continuously moving. 
• Particles of mater attract each other.

Question 1:  The mass per unit volume of a substance is called density (density = mass/volume). Arrange the following in order of increasing density − air, exhaust from chimney, honey, water, chalk, cotton, and iron. 

Answer: The given substances in the increasing order of their densities can be represented as: 

Air < Exhaust from chimney < Cotton < Water < Honey < Chalk < Iron  

Explanation:  Air is the mixture of gases. Chimney exhaust is also a mixture of gases; along with some heavier particles, such as ash. This makes the density of chimney exhaust more than air. Cotton is a porous solid and which has lot of air trapped within pores. This makes its volume more than water. Therefore, it is less dense than water.

Question 2:  (a) Tabulate the differences in the characteristics of states of matter. (b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

Answer:  (a) The differences in the characteristics of states of matter are given in the following table. 

The difference in the characteristics of the three states of matter.

(b) Rigidity:  The greatest force of attraction between particles and close packing of particles make solids rigid. Rigidity is one of the unique properties of solids. Because of rigidity, a solid can resist from getting distorted. Because of rigidity a solid has definite shape and volume. Rigidity is negligible in fluid and gas.

Compressibility:  Compressibility is one of the most important characteristics of gas. Because of lot of space between particles, a gas can be compressed to a great extent.

Liquid and solid cannot be compressed because of the least space between their particles.

Fluidity:  The ability to flow is called fluidity. The less force of attraction and more space between particles make liquid and gas to flow. That’s why liquid and gas are called fluid.

Filling of a gas container:  Liquids do not fill a gas container completely, while gases fill the gas container completely in which it is kept. This is because the particles of gas can move in all the directions.

Shape:  Solids have fixed shape. Liquid and gas take the shape of the container in which they are kept. This happens because of less force of attraction and more kinetic energy between particles of liquids and negligible force of attraction and highest kinetic energy between particles of gas.

Kinetic energy:  The kinetic energy of particles of solid is the minimum. They only vibrate at their fixed position. The kinetic energy of particles of liquid is more than that of solid. But they can slide above one another. The kinetic energy of particles of gas is the maximum.

Density:  The mass per unit volume of a substance is called density. The density of solid is highest, of liquid is less than solid and of gas is minimum.

Question 3:  Give reasons:  (a) A gas fills completely the vessel in which it is kept. (b) A gas exerts pressure on the walls of the container. (c) A wooden table should be called a solid. (d) We can easily move our hand in air, but to do the same through a solid block of wood, we need a karate expert.

Answer:  (a) There is little attraction between particles of gas. Thus, gas particles move freely in all directions. Therefore, gas completely fills the vessel in which it is kept.

(b)  Because of negligible force of attraction between particles of gas, the particles of gas have the highest kinetic energy. These properties enable the particles of gas to move in all directions and hit the walls of container from all sides. Because of this a gas exerts pressure on the walls of the container in which it is kept.

(c) A wooden table has a definite shape and volume. It is very rigid and cannot be compressed i.e., it has the characteristics of a solid. Hence, a wooden table should be called a solid.

(d) Particles of air have large spaces between them. On the other hand, wood has little space between its particles. Also, it is rigid. For this reason, we can easily move our hands in air, but to do the same through a solid block of wood, we need a karate expert.

Since, air is gas, so its particles are loosely packed and there is negligible force of attraction between its particles. Because of that we can easily move our hand in air. But wood is a solid, so the force of attraction between its particles is greatest. The particles of wooden block are closely packed. That’s why we cannot move our hand through a solid block of wood. However, a karate expert can exert required pressure to break the great force of attraction of the particles of a solid wooden block.

Question 4:  Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why. 

Answer: During freezing of water, some space between the particles of water is left vacant with some air trapped between them. These empty spaces having air in them makes the density of ice; lower than that of water. That’s why ice floats on water.

Question 1: Convert the following temperatures into the Celsius scale. (a) 300 K (b) 573 K

Answer: (a) 300 K = (300 − 273)°C = 27°C (b) 573 K = (573 − 273)°C = 300°C

Question 2: What is the physical state of water at (a) 250°C  (b) 100°C

Answer: (a) Water at 250°C exists in gaseous state.

(b) At 100°C, water can exist in both liquid and gaseous form. At this temperature, after getting the heat equal to the latent heat of vaporization, water starts changing from liquid state to gaseous state.

Question 3:  For any substance, why does the temperature remain constant during the change of state? 

Answer: During a change of state, the temperature remains constant. This is because all the heat supplied to increase the temperature is utilized (as latent heat) in changing the state by overcoming the forces of attraction between the particles. Therefore, this heat does not contribute in increasing the temperature of the substance. 

Question 4:  Suggest a method to liquefy atmospheric gases. 

Answer:  Atmospheric gas is liquefied by increasing pressure and decreasing temperature.

PAGE NO. 10

Question 1:  Why does a desert cooler cool better on a hot dry day?

Answer: Desert cooler works on the basis of evaporation. In hot and dry days the moisture level is very low in atmosphere which increases the rate of evaporation. Because of faster evaporation, cooler works well. That’s why desert cooler cool better on a hot dry day.

When a liquid evaporates, the particles of the liquid absorb energy from the surroundings to compensate the loss of energy during evaporation. This makes the surroundings cool. 

In a desert cooler, the water inside it is made to evaporate. This leads to absorption of energy from the surroundings, thereby cooling the surroundings. Again, we know that evaporation depends on the amount of water vapour present in air (humidity). If the amount of water vapour present in air is less, then evaporation is more. On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more.  That is why a desert cooler cools better on a hot dry day. 

Question 2:  How does water kept in an earthen pot (matka) become cool during summers?

Answer: Water from porous wall of earthen pot evaporates continuously, which lowers the temperature of water kept in the earthen pot. In summer moisture level is very low in the atmosphere, which increases the rate of evaporation as evaporation is inversely proportional to the moisture level in atmosphere. That is why in summer water kept in earthen pot becomes cool.

Question 3: Why does our palm feel cold when we put some acetone or petrol or perfume on it?

Answer: When we put some acetone or petrol or perfume on our palm, it evaporates. During evaporation, particles of the liquid absorb energy from the surrounding or the surface of the palm to compensate for the loss of energy, making the surroundings cool. Hence, our palm feels cold when we put some acetone or petrol or perfume on it.

Question 4: Why are we able to sip hot tea or milk faster from a saucer than a cup? 

Answer: When hot tea or milk is kept in a saucer, the liquid is exposed over a larger surface area as compared to in case of the liquid being kept in a cup. The larger surface area enables the faster cooling. That’s why we are able to sip hot tea or milk faster from a saucer rather than from a cup.

Question 5:   What type of clothes should we wear in summers? 

Answer: In summer, it is preferred to wear light-coloured cotton clothes because light colour reflects heat and cotton materials have pores that absorb sweat, facilitating their evaporation hence causing a cooling effect in the skin.

Question 1: Convert the following temperatures into the Celsius scale. (a) 293 K (b) 470 K

Answer: Temperature in Celsius scale = Temperature in Kelvin scale – 273

(a) 293K= (293 – 273)°C = 20°C

(b) 470K= (470 – 273)°C = 197°C

Question 2: Convert the following temperatures into the Kelvin scale.  (a) 25°C (b) 373°C

Answer: Temperature in Kelvin scale = Temperature in Celsius scale + 273

(a) 25°C = (25+273)K = 298K

(b) 373°C = (373+273)K = 646K

Question 3: Give reasons for the following observations. (a) Naphthalene balls disappear with time without leaving any solid. (b) We can get the smell of perfume while sitting several metres away.

Answer: (a) At room temperature, naphthalene balls undergo sublimation wherein they directly get converted from a solid to a gaseous state without having to undergo the intermediate state, i.e., the liquid state.

(b) Perfumes vaporize very fast and its vapours diffuse into air easily. That is why we can smell perfume sitting several meters away. 

Question 4: Arrange the following in increasing order of forces of attraction between the particles – water, sugar, oxygen.

Answer:  Oxygen < Water < Sugar.

Explanation: Oxygen is a gas, thus force of attraction is negligible between particles. Water is a liquid, thus force of attraction between particles is more than liquid and less than solid. Sugar is a solid, thus force of attraction between particles is greatest.

Question 5: What is the physical state of water at — (a) 25°C                       (b) 0°C                               (c) 100°C?

Answer: (a) At 25°C – water is in liquid state. (b) At 0°C – water is in solid state. (c) At 100°C – water is in transition state, i.e. in liquid and gas both.

Question 6: Give two reasons to justify: (a) water at room temperature is a liquid. (b) an iron almirah is a solid at room temperature.

Answer: (a) At room temperature (25 °C), water is a liquid because it has the following characteristic of liquid:

(i) Water has definite volume, but not definite shape as it takes the shape of the container in which it is kept. (ii) Water flows at room temperature.  

(b) An iron almirah is a solid at room temperature because: (i) It has definite shape. (ii) It has definite volume.

Question 7: Why is ice at 273 K more effective in cooling than water at the same temperature?

Answer: At 273K ice requires more latent heat to melt into water, while water at 273K requires less latent heat; to come to the room temperature. So, ice at 273 K is more effective in cooling than water at the same temperature.

Question 8: What produces more severe burns, boiling water or steam?

Answer: Steam produces more severe burns than boiling water. This is because steam has more energy than boiling water, present in it in the form of latent heat of vaporization.

Question 9: Name A, B, C, D, E and F in the following diagram showing change in its state:

Answer: A: Melting (or) fusion (or) liquefaction B: Evaporation (or) vaporization C: Condensation D: Solidification E: Sublimation F: Sublimation

Class 9 Science NCERT Solutions Chapter 1 Matter in Our Surroundings

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NCERT Solutions for Chapter 1 Matter in Our Surroundings Class 9 Science

Which of the following are matter ?

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

The mass per unit volume of a substance is called density (density = mass/volume).

Air, Exhaust from chimneys, cotton, water, honey, chalk, and iron.

→ Rigidity: It is the property of matter to resist the change of its shape. → Compressibility: It is the property of matter in which its volume is decreased by applying force. → Fluidity: It is the ability of matter to flow. → Filling a gas container: On filling a gas takes the shape of the container. → Shape: Having definite boundaries. → Kinetic Energy: It is the energy possessed by the particles of matter due to its motion. → Density: It is the ratio of mass with per unit volume.

(a)  The force of attraction between particles of gas is negligible. Because of this, particles of gas move in all directions. Thus, a gas fills the vessel completely in which it is kept.

(b)  Particles of gas move randomly in all directions at high speed. As a result, the particles hit each other and also hit the walls of the container with a force. Therefore, gas exerts pressure on the walls of the container.

(c)  A wooden table has fixed shape and fixed volume, which are the main characteristics of solid. Thus a wooden table should be called a solid. (d) Particles of the air have large spaces between them. On the other hand, wood has little space between its particles. Also, it is rigid. For this reason, we can easily move our hands in the air, but to do the same through a solid block of wood, we need a karate expert.

► 300 K = (300 - 273)°C

► 573 K = (573 - 273)°C

What is the physical state of water at:

(b)  Since water boils at this temperature thus it   can exist in both liquid and gaseous form. At this temperature, after getting the heat equal to the latent heat of vaporisation, water starts changing from liquid state to gaseous state.

For any substance, why does the temperature remain constant during the change of state ?

(For Conversion Process we must know, Kelvin is an SI unit of temperature, where 0°C = 273 K approx.)

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CBSE Class 9 Science Chapter-1 Important Questions - Free PDF Download

Chapter 1 of science in class 9 talks about matters of our surroundings. Many students consider science as a difficult and challenging subject as they face difficulty in understanding the concepts and theories of this subject. The best way to overcome this problem is to start practising Class 9 Science chapter 1 important questions. Solving these questions regularly will help the students to improve their skills on this subject. Thus, scoring good marks in the exams becomes easy for them. M atter in our surroundings class 9 important questions guides students in their preparation to make them efficient. Vedantu is a platform that provides free CBSE Solutions (NCERT) and other study materials for students. Maths Students who are looking for the better solutions, they can download Class 9 Maths NCERT Solutions to help you to revise complete syllabus and score more marks in your examinations.

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Very Short Answer Questions 1 Mark 

1. Which of the following matter? 

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, the smell of perfume. 

Ans: As we can define matter as any ‘physical substance’, hence almonds,  air, chair, the smell of perfume, cold drink and smell can be considered as matter. 

2. Convert the following temperature to a Celsius scale: 

i) The temperature is 300 K. 

Ans: When we use: K = 273 + ⁰C:

                                  ⁰C = K - 273

                                        = 300 - 273

                                        = 27⁰C

ii) The temperature is 573 K 

                                  ⁰C = 573 - 273

                                       = 300 ⁰C

3. What is the physical state of water at:  

(a) A temperature of 250 ⁰C 

Ans: The boiling point of water is 100 ⁰C, hence the physical state of water at 250⁰C will be gaseous.

(b) A temperature of 100 ⁰C 

Ans: The boiling point of water is 100 ⁰C, hence at 100 ⁰C water is in the gaseous state. 

4. For any substance, why does the temperature remain constant during the change of state? 

Ans: The reason behind the temperature of substance or matter remaining constant during a change of state is that during the change of state all of the heat or energy provided to particles of matter is utilized to take the particles of matter apart from each other. 

5. Suggest a method to liquefy atmospheric gases. 

Ans: One method to liquefy atmospheric gases is to decrease the temperature and increase the pressure. 

6. Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, and oxygen. 

Ans: The order of increasing forces of attraction between the particles is as  follows: 

Oxygen< water< sugar.

7. What is the physical state of water at- 

(a) A temperature of 25 ⁰C? 

Ans: The physical state of water at 25 ⁰C is liquid. 

(b) A temperature of ⁰C? 

Ans: The physical state of water at ⁰C is solid. 

(c) A temperature of 100⁰C? 

Ans: The physical state of water at 100⁰C is gas.

8. If the humidity in the air increase then the rate of evaporation: 

(a) decrease 

(b) increase 

(c) remain same 

(d) both (b) and (a) depending upon the temperature  

Ans: The correct option is (a) decrease. 

9. Which of the following statements is correct? 

(a) boiling is a bulk phenomenon and evaporation is a surface phenomenon (b) boiling is a surface phenomenon and evaporation is a bulk phenomenon (c) boiling and evaporation both are a surface phenomenon 

(d) boiling and surface both are bulk phenomenon 

Ans: The correct option is (a) boiling is a bulk phenomenon and evaporation is a  surface phenomenon. 

10. If the temperature of a place is increase then evaporation: 

(d) none of the above  

Ans: The correct option is (b) increase. 

11. Which of the following has the least inter atomic spacing? 

(a) solid 

(b) liquid 

(c) gases 

(d) plasma  

Ans: The correct option is (a), solid.

12. If you decrease the surface area and increase the temperature, then the  rate of evaporation 

(a) increase 

(b) decrease 

(d) may increase or decrease depending upon other factors 

Ans: The correct option is (c), remain the same. 

13. What will be the corresponding temperature in degree centigrade for 300 K:  

(a) 30 ⁰C 

(b) 300 ⁰C 

(c) 27 ⁰C 

(d) 673 ⁰C 

Ans: The correct option is (c), 27 ⁰C. 

14. Liquid to gas and gas to liquid changes are called: 

(a) vaporization and condensation 

(b) condensation and vaporization 

(c) sublimation and condensation 

(d) condensation and sublimation  

Ans: The correct option will be (a), vaporization and condensation. 

15. Physical state of water at is respectively 

(a) liquid, solid, and gas 

(b) solid, liquid, and gas 

(c) solid, gas, and liquid 

(d) gas, solid, and liquid

Ans: The correct option is (a), liquid, solid and gas. 

Short Answer Questions                                                   2 Marks 

1. Give reasons for the following observation: 

The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close. 

Ans: When it is a higher temperature the diffusion rate (movement) of particles will be very fast when compared to the diffusion rate of particles at a lower temperature and since the temperature of hot sizzling food is higher than cold food, the smell of hot sizzling food will be reaching us from several meters away. 

2. The mass per unit volume of a substance is called density. (density = mass/volume). 

Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton, and iron. 

Ans: The correct order of increasing densities of the substances is as follows: Air < exhaust from chimneys< cotton< water< honey< chalk< iron. 

3. Liquids generally have a lower density as compared to solids. But you must have observed that ice floats on water. Find out why. 

Ans: Ice floats on the water since there is a large empty space inside the 3D structure of ice due to which it becomes less in weight as compared to water and can float on water. 

4. Why does a desert cooler cool better on a hot dry day? 

Ans: In a desert cooler, when hot air enters through the straw mates it evaporates the water at a fast rate because the rate of evaporation is faster on a hot dry day.  And because of the faster evaporation rate, it cools the air more conveniently than on a dry hot day. 

5. How does the water kept in an earthen pot (matka) become cool during summer? 

Ans: Evaporation happens through the small pores on it causing a cooling effect, in an earthen pot. Therefore water kept in an earthen pot becomes cool during summer because of continuous evaporation. 

6. Why does our palm feel cold when we put some acetone or petrol or perfume on it? 

Ans: As a perfume, petrol and perfume are volatile liquids, if put on our palm they will be absorbing heat from our palm and cause cooling. 

7. Why are we able to sip hot tea or milk faster from a saucer rather than a  cup? 

Ans: When we use a saucer instead of a cup the surface for evaporation to occur will be increased resulting in faster evaporation of particles of tea or milk and allowing it to cool faster and taking a sip becomes easier. 

8. What type of clothes should we wear in summer? 

Ans: We must wear the type of clothes which allow easy evaporation since evaporation causes cooling. And as the cotton absorbs sweat well and allows easy evaporation, we must prefer wearing cotton clothes in summer. 

9. Convert the following temperatures to the Celsius scale.  

a) The temperature is 293 K 

Ans: When we use: ⁰C = K - 273 

                                        = 293 - 273 

                                       = 20 ⁰C

b) The temperature is 470 K 

= 470 - 273 

= 197 ⁰C 

10. Convert the following temperatures to the Kelvin scale. 

a) The temperature is 25 ⁰C

Ans: When we use: K = ⁰C + 273 

                                       = 25 + 273

                                      = 298 K 

b)The temperature is 373 ⁰C 

                                       = 373 + 273

                                       = 656 K 

11. Give a reason for the following observations. 

a) Naphthalene balls disappear with time without leaving any solid. 

Ans: Sublimation can be defined as the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. Naphthalene balls will be having the property of sublimation because of which they directly vary from solid to gaseous state without a conversion into liquid. Hence, naphthalene balls will be vanishing with time leaving no solid. 

b)We can get the smell of perfume sitting several meters away. 

Ans: Volatile substances such as perfumes change from liquid state to gaseous state very fast which allows them to diffuse and mix up with the air particles to reach our nostrils. Therefore we get the smell of perfume sitting several metres away. 

12. Give two reasons to justify - 

a) Water at room temperature is a liquid. 

Ans: For a temperature of <0 ⁰Cwater is in solid-state, for 0⁰C → 100⁰C → water is in a liquid state and for temperature >100 ⁰C water is in a gaseous state. Since room temperature always lies between 0 ⁰C and 100 ⁰C and within this range the physical state of water is liquid so water is liquid at room temperature. 

b) An iron almirah is a solid at room temperature. 

Ans: Since the room temperature is very less than the melting point of iron hence an almirah made up of iron will be a solid at room temperature.

13. Why is ice at 273 K more effective in cooling than water at the same temperature? 

Ans: Ice will be producing a more intense cooling effect as compared to water at  273 K because at 273 K ice will be absorbing latent heat of melting from the surroundings and will be getting converted into water. Therefore ice at 273 K is more effective in cooling than water at the same temperature. 

14. What produces more severe burns, boiling water or steam? 

Ans: When the steam gets converted into boiling water it releases latent heat of water which results more severe burns when we compare it to boiling water. 

15. What is evaporation? What are the factors affecting it? 

Ans: Evaporation can be defined as the process of conversion of a substance from its liquid state to a gaseous state at any temperature below its boiling point. 

Evaporation will be dependant on the factor below: 

a) Surface area 

b) Temperature 

c) Humidity  

d) Wind speed  

16. What happens when we apply pressure to the particles of matter? 

Ans: Pressure can be defined as the force applied per cross-sectional area.  Therefore when we apply pressure to the particles of matter, the force applied brings the particles closer to each other. 

17. Define latent heat of vaporization and latent heat of fusion. 

Ans: The heat energy required to change 1 kg of a substance from its liquid state to a gaseous state at atmospheric pressure without changing its temperature is known as latent heat of vaporization. 

18. If the melting point of object A is high then what state do you expect it to be at room temperature? 

Ans: The temperature at which a substance changes its state from solid to liquid is called its melting point. At a temperature below melting point, the substance will be in solid-state. Therefore, if the melting point of an object A is high then the object will be in solid-state. 

19. What happens when the temperature of the solids increase? 

Ans: When we increase the temperature of the solid, we are giving energy to it.  That energy is utilized in increasing the kinetic energy of the particles and as a  result, the speed of the particles is increased and they vibrate more freely. Once the particles overcome the force of attraction between them they start moving more freely. 

20. When heat is being supplied to a solid, then what does the heat energy do  to the particles of the solid? 

Ans: The heat energy increases the kinetic energy of the particles which allows the particles to overcome the forces of attraction and start moving more freely and changing the state from solid to liquid. 

21. Why is it that on increasing the wind speed the rate of evaporation increases? 

Ans: If we increase the speed of the wind, then they will be blowing away with them.  The water vapours in the air are blown away when the speed of wind is increased,  making room for more water vapours and increasing the rate of evaporation. 

22. Why do we say that evaporation is a surface phenomenon? 

Ans: Only the particles at the surface of the liquid absorb energy and get converted into vapours, therefore evaporation is called a surface phenomenon. 

Long Answer Questions 3 Marks 

1. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show? 

Ans: It is given that a diver is able to cut through water in a swimming pool. This is representing that the particles of water will be held together by weak forces of attraction between them and when any external force is applied the particles can be separated.

2. What are the characteristics of the particles of matter?  

Ans: The particles of matter have the following characteristics: 

i. The particles of matter are in continuous motion. 

ii. There are gaps between the particles of matter. 

iii. There is a force of attraction between the particles of matter which keeps them together. 

3.  

(a) Tabulate the differences in the characteristics of states of matter. Ans: Tabular differences in characteristics of matters are given below: 

(b) Comment upon the following: rigidity, compressibility, fluidity, filling a  gas container, shape, kinetic energy, and density. 

Rigidity → The property of matter to maintain its shape when external forces are applied to it is known as rigidity. Solids have this property.

Compressibility → The property of matter to allow compression when high pressure is applied to it is known as compressibility. Some Liquids and all gases have this property. 

Fluidity → The property of matter to flow and change in its shape when external forces are applied to it is known as fluidity. Both liquids and gases have this property. 

Filling a gas container → Gases are fluid in nature and are highly compressible which allows them to be filled within a vessel at high pressure. A large volume of gas can be filled in a container of less volume making it suitable and more cost-efficient for transportation. 

Shape → Only solid objects have well-defined shapes while liquids can acquire any shape depending on the container they are kept in and gases don’t have any shape. 

Kinetic energy → The particles of a matter are continuously in motion and thus have kinetic energy. As the particles in solids have the least movement, the kinetic energy of solids is the least. The particles of gases have the freest movements and hence they have the highest kinetic energy. The order of kinetic  energies for different types of matters is: solid < liquid < gas  

Density → Density of any substance can be explained as Mass per unit volume i.e. density = mass/volume. 

4. Give reasons 

(a) A gas fills completely the vessel in which it is kept. 

Ans: The particles of gas have negligible attraction force between them because of which the particles move freely in all directions filling the whole container the gas is kept in. 

(b) A gas exerts pressure on the walls of the container. 

Ans: The particles of gas move freely due to which they collide with the container walls continuously and randomly. Therefore the collision of particles on the container walls exerts pressure on the walls.

(c) A wooden table should be called a solid. 

Ans: Solids have rigid and fixed particles and have a definite shape and clear boundaries. Since a wooden table possesses all the qualities of a solid, it should be called a solid. 

(d) We can easily move our hand in the air but to do the same through a solid block of wood we need a karate expert. 

Ans: Since air is a gas and the forces of attraction between the particles of gas are very less which makes it easy to separate the particles with the help of an external force and hence we can easily move our hand in the air. Whereas in the case of solids the forces of attraction are very strong and we need a very high force to separate the particles of a solid and hence we need a karate expert for it. 

5. Name A, B, C, D, E, and F in the following diagram showing changes in its state. 

A is fusion or heating or melting.  

B is vapourisation. 

C is cooling or Condensation. 

D is cooling or solidification.

E is sublimation.  

F is solidification. 

6. Are the three states of matter inter-convertible? How can they interconnect? 

Ans: Yes, the three states of matter can be converted into each other. 

The three states of matter are interconvertible as shown below: 

a) By heating we can convert solids into liquids and by cooling we can convert liquids into solids. 

b)We can convert liquids into gases by vaporization and we can convert gases to liquids by condensation. 

c) Using sublimation we can convert solids into gases and vice versa and using condensation we can convert liquids into solids. 

7. How does evaporation cause cooling? 

Ans: During evaporation, the particles of a liquid absorb the heat from the surface and are converted into vapours utilizing the absorbed heat. This absorption of heat from the surface will be producing a cool surface. 

8. Why should we wear cotton clothes in summer? 

Ans: Since cotton is a good absorbent of water, it absorbs all the sweat from our body and allows easy and fast evaporation. The sweat absorbs heat from our body and evaporates which makes us feel cooler during a hot summer day. That is why we should wear cotton clothes in summer. 

9. Differentiate between physical and chemical change? 

Ans: The difference physical and chemical change is given below 

10. A solution of H₂SO₄ is labeled 40%. The density of the solution is  1.3 gm/l. What is the concentration of the solution in %(m/v)? 

Ans: The given concentration of the solution is 40%. 

Therefore, 100 gm of the solution contains 40 g of H₂SO₄  

Density = \[\frac{mass}{volume}\]

1.3gm/l = \[\frac{100 g}{volume}\]

Volume of the solution = \[\frac{100}{1.3}\]

= \[\frac{100}{1.3}\] ml

So, = \[\frac{100}{1.3}\] of the solution contains 40g of H₂SO₄

Therefore, 100 ml of solution will contain \[\frac{100 \times 40 \times 1.3}{100}\] g of H₂SO₄

= 52 g of H₂SO₄

Therefore, the concentration is 52% (m/v).

11. What is the state of inter particle distance inside a solid, liquid, and gas? 

Ans: In a solid, the forces of attraction between the particles are very high and hence the particles of a solid will be very close to each other and the inter particle distance is the least. 

In a liquid, the forces of attraction between the particles are very weak, and therefore the particles of a liquid will not be closely packed with each other and the inter-particle distance is large.  

In a gas, the forces of attraction between the particles are almost negligible or extremely weak and therefore the particles of a gas are very loosely packed and are very far from each other and the inter particle distance is largest. 

12. Why is it that to smell cold food, we have to go close but the smell of hot food reaches us several meters away? 

Ans: When the particles are at higher temperature, their movements are fast and therefore they can travel up to several meters. Hence the hot food’s smell will be reaching us several meters away. 

At lower temperatures, the movements of particles are not very fast and particles do not have enough kinetic energy to travel a distance of several meters.  Therefore we have to go close to smell cold food. 

13. Why is it that a wooden chair should be called a solid and not a liquid? 

Ans: A wooden chair is a rigid object, the particles of a wooden chair are tightly packed with each other, the chair has a definite shape and the chair has negligible compressibility. Since a wooden chair possesses all the properties of a solid and not of a liquid, it should be called a solid, not a liquid.

14. Give an experiment to show that ammonium chloride undergoes sublimation. 

Ans: Experiment for representing the sublimation of ammonium chloride (NHCl₄): 

a) Take a crystal of ammonium chloride (NHCl₄) inside a china dish and an inverted funnel. 

b) With the help of a burner, heat the ammonium chloride (NHCl₄) crystals. 

c) When the ammonium chloride (NHCl₄) crystal is heated, vapours of (NHCl₄) and the Ammonium chloride (NHCl₄) which is solidified along the walls at the beaker’s upper end is observable. 

d) This experiment shows that solid ammonium chloride (NHCl₄) undergoes solidification. It directly changes to vapour state from a solid state, it does not convert into liquid. 

15. What is distillation and fractional distillation? What is the basic property that separates the two methods? 

Ans: The process of distillation is used for separating the components of a  mixture containing two liquids, having different boiling points and both liquids boil without decomposition. 

The process of fractional distillation is used for separating the components of a  mixture containing more than two liquids having a boiling point difference of less than 25 K. 

The basic property that separates these two methods is: 

Using distillation we can separate only those components which have a  significant difference in their boiling points. While fraction distillation is used when the difference in boiling points is less.

Many students don’t have a strong core knowledge on the subject of science and face difficulty in understanding the basics of the chapters. Due to which they lose a lot of marks in the final exams. To avoid these, students need to formulate a better preparation plan where they should give more emphasis to the practice of class 9th science chapter 1 important questions. Regular practice will help them to improve and be more confident about their own knowledge.

The questions that are included in chapter 1 science class 9 important questions are most likely to come in the exams. Thus, preparing the students better and efficient. Students can download the pdf of class 9 chapter 1 science important questions from the Vedantu site. This pdf is available for free. After downloading the pdf, students can refer to it at every stage of their preparation.

Important Question of Science Class 9 Chapter 1

Students will learn a lot of things from the chapter 'matters in our surroundings, let's discuss some of those things:

The matter is considered as a substance from which our cosmos is made of. Any substance with some mass, that takes volume and which can get comprehended by the senses is termed as a matter. There are a lot of exceptions in this case such as heat, light energy, electrical energy, sound energy, magnetism, vacuum, and shadow. This all is not considered a matter because they don't have mass and they don't take any place.

The substance 'matter' is believed to be composed of small constituent parts. Matters have minimal and minute units. Taking a glance on them is very difficult even with a high-power microscope.

To understand more simply, everything around you is made up of matter. Atoms and compounds of everything are made with small parts of matter. These atoms are responsible for building the things that we see and touch every day.

Characteristics of Matter

The different characteristics of matter are listed below:

The matter is a substance which is made up of small particles.

It is believed that the particles consist of intermolecular spaces between them.

The particles in the matter have a locomotive nature due to the kinetic energy inside them. When there is a surge in the temperature, the motion of particles intensifies.

The bits in the matter attract each other, but this reciprocal force of full becomes operational only when the particles are very close to each other. In solids, the particles are firmly held, which is why it is believed that they have a superior force of attraction. Whereas in gases, particles are loosely held; thus, they have a minimal force of attraction.

Nature of Matter

Depending upon the physical state of different materials or substances, the nature of matter is classified into three categories:

Solids are substances where the particles are held very close to each other due to a strong intermolecular force. The particles are so tightly held at their place that they can have only vibratory motions and nothing else. As the particles are tightly held, therefore solids have a definite shape and definite volume. Some examples of solids are wood, iron, glass, etc. Students while practising important question of science class 9 chapter 1 will learn more about this substance and that too in a straightforward way.

Those substances where the intermolecular forces are weak enough to allow the movement of particles are generally known as liquids. These particles are also closely held with each other, but they have more freedom of movement than the particles of solid. Liquids are substances with a definite volume but with no definite shape. These substances generally take the shape of the container in which they are stored. Some examples of liquid substances are milk, water, etc. To gain more detailed knowledge on this particular substance, students have to continue practising ch 1 science class 9 important questions without fail.

These types of substances have very weak intermolecular forces between their particles or molecules, so the molecules have the freedom to move. The distance between each particle in a gas is bigger if compared to the distance between particles in solids and gases. Gases do not have a fixed shape or a definite volume. These substances fully occupy the containers in which they are stored. Some examples of gases are air, hydrogen, oxygen, methane, etc. By practising important questions for class 9 science chapter 1 regularly, students can gain more knowledge on this particular substance.

These above three states of matter can be transformed from one form to the other just by changing the environment's temperature and pressure conditions. The composition of matter is also used to determine its nature. If a matter is composed of more than one particle, then it is considered as a mixture, but when it contains only one particle, then it is termed as a pure substance. Mixtures are further classified into homogeneous and heterogeneous categories. Pure substances can also get divided into elements and compounds.

All the information that you have read till now are some basics of the chapter 'Matter in our surroundings. But there is more to this chapter, and things will get complicated after getting inside the different topics of the chapter. Students find the theories of this chapter complicated and thus are incapable of scoring good marks, but by practising class 9 science chapter 1 important questions regularly, students can avoid fewer marks.

Matter in Our Surroundings Class 9 Important Questions

Some of the important questions that the students might face in the exams are as follows:

Mention the technique which is used for separating the substances from the mixture.

What is the difference between a homogeneous mixture and a heterogeneous mixture?

What do you understand by the term Matter?

State the different characteristics of matter.

What is the nature of matter? Explain in a brief way.

State the points which show that a physical Change is different from a chemical change.

What are the reasons which cause a matter to change its state from one form to another?

What do you understand by the term element?

What do we call a mixture of salt and sugar in our regular lives?

State the three states of matter based on the distance between the molecules.

State the process using which the seawater can get purified.

What are the properties of a solid?

State the properties of a liquid.

Mention the properties of a gas.

Which state of matter is related to Boyle's law.

CBSE Class 9 Chapter 1 MCQs

1. Due to which among the following phenomena, the water kept in the earthen pot becomes cool during summers?

Transpiration

Evaporation

2.  Which of the following conditions will increase the evaporation of water?

Increase in temperature of the water

Decrease in temperature of the water

Less exposed surface area of water

Adding common salt to the water

3. Which of the following is the boiling point of water at sea level?

Answers: 1 (d), 2 (a) and 3 (c)

Benefits of Class 9th Science Chapter 1 Important Questions

Students who are facing problems in chapter 1 of class 9 are suggested to practice important questions of ch 1 science class 9 so that they can take advantage of this and prepare well. Some of the benefits of this list of questions are:

The questions are taken keeping in mind the syllabus and the format imposed by the CBSE board for class 9 students because any deviations from that can cost students a lot of marks.

The questions are selected under the guidance of some expert teachers who have years of experience in this field. They select questions according to the intellectual capability of the students.

The questions included in the list of chapter 1 science class 9 important questions are most likely to come in the exams, thus making students' preparation better and efficient.

The questions are given with solutions which are explained in a detailed manner.

Important Related Links for CBSE Class 9 

Conclusion .

In conclusion, the availability of important questions for CBSE Class 9 Science Matter in Our Surroundings is a valuable resource for students preparing for their examinations. These important questions cover key topics and concepts related to the chapter, helping students deepen their understanding of the properties of matter, changes of state, and the behavior of particles. Practicing some important questions, students can enhance their knowledge and improve their problem-solving skills. These questions encourage critical thinking and application of scientific principles, preparing students to answer exam questions effectively.

Engaging with these important questions enables students to consolidate their understanding of the chapter, identify areas where they need further clarification, and strengthen their grasp of the subject. They also serve as a valuable revision tool, helping students review and reinforce the concepts they have learned.

FAQs on Important Questions for CBSE Class 9 Science Matter in Our Surroundings 2024-25

1. Where can I find extra questions for CBSE Class 9 Science Chapter 1- Matter in Our Surroundings?

There are several e-learning sites that provide more practice questions. On Vedantu, you may find the most frequently asked questions for each scientific chapter. Vedantu is a leading learning portal that offers all of the required exam preparation materials such as example papers, NCERT Answers, crucial questions, revision notes, and so on. Important questions for Chapter 1- Matter in Our Surroundings and other chapters, as well as solutions, are available on Vedantu's website for Class 9 CBSE students. Subject matter experts with sufficient expertise and experience in the topic prepare the replies. The key CBSE Class 9 Science Chapter 1 questions have been prepared in a PDF file for students to practice before examinations.

2. What are the two recently discovered states of matter?

Apart from the three-commonly known states of matter, there exist other two states of matter which are much talked about: Plasma and Bose-Einstein Condensate. 

Plasma: Plasma state is the 4th state of matter which is an ionized gas. Plasma neither has a definite volume nor a definite shape. It can be defined as a gaseous substance into which sufficient energy is provided to free electrons from atoms or molecules and to allow both species i.e. ions or electrons to co-exist. Examples of plasma are Stars, lightning, etc. Plasma is also present inside the fluorescent lights.

Bose-Einstein Condensate:   Bose-Einstein Condensate (BEC) is a state of matter of a dilute gas of bosons (a boson is a particle that follows Bose-Einstein Statistics) cooled to a temperature very close to absolute zero. In simple words, BEC is formed by cooling a gas of extremely low density.

3. Can matter exist in all three states?

Indeed, materials may exist in all three states at the same time. At differing temperature and pressure circumstances, the three states of matter interconvert. In other words, pressure and temperature determine the state of a substance, i.e. whether it is solid, liquid, or gas. As water boils, it turns into vapour, and when it freezes at its freezing point, it turns into ice. It is critical to realise that the difference between different states of matter is caused by the location of component particles. As a result, these particles' characteristics can alter as a result of temperature and pressure.

4. What is the difference between boiling and evaporation?

Boiling is a bulk phenomenon whereas evaporation is a surface phenomenon. Particles from the bulk of the liquid change into vapour state in the process of boiling. However, in the process of evaporation, particles from the surface change into the vapour state by gaining enough energy from the atmosphere that weakens the force of attraction present into the liquid to change it into vapour form.

5. What is the significance of using Vedantu’s Important Questions for studying Chapter 1 Matter in Our Surroundings of Class 9 Science?

Every crucial question from the Chapter- Matter in our Surroundings has been hand-picked by Vedantu's expert pros. Vedantu's Crucial Questions for Chapter 1 Matter in Our Surroundings of Class 9 Science has around 50 critical questions from the course. In tests, these questions are worth one to five points. Working through these questions will give you with the necessary chapter revision. It will also assist you in understanding how to develop optimal replies for various exam questions.

6. What are some important questions from Chapter 1 Matter in Our Surroundings of Class 9 Science for exams?

Matter in Our Surroundings contains many important experiments, definitions, and reasoning questions that can be asked in the exams. Some of the examples of these questions are as follows:

Enlist the characteristics of particles of matter.

Suggest a method to liquefy gases.

Why is it that on increasing the wind speed the rate of evaporation increases?

Define latent heat of vaporization and latent heat of fusion.

For over 50 such important questions from this chapter, visit Vedantu .

7. Are the important questions for Chapter 1 Matter in Our Surroundings of Class 9 Science accessible offline?

Yes, the important questions for Chapter 1 Matter in Our Surroundings of Class 9 Science are easily accessible offline by downloading its PDF file in the following simple steps.

Visit Vedantu and choose the subject and the chapter you want. 

On the subsequent page, scroll down and look for the option to "Download PDF."

This will redirect you to a new page containing the link to download the required PDF promptly.

For an even smoother download process, install the Vedantu mobile app and access all the content easily from your phone.

8. How can you show that one crystal of potassium permanganate contains millions of tiny particles?

Dissolve two or three crystals of potassium permanganate and dissolve them in 100 ml of water. Take 10 ml of this solution and put it in another container with 90 ml of water. Take 10 ml of this new solution and again dissolve it in 90 ml of water. Dilute the solution six to eight times. You will find that water still remains coloured after much dilution. This proves that one crystal of potassium permanganate must contain millions of tiny particles that keep on dividing in the water.

9. How can evaporation cause cooling? Give examples.

As a liquid evaporates, its particles collect energy from the surrounding environment in order to recoup the energy lost during evaporation. As energy is taken from the surroundings, the surroundings get colder. In the summer, for example, people sprinkle water over the roofs of buildings to keep them cool. Our body's sweating system functions similarly. As we perspire on a hot day, our perspiration evaporates, which helps to lower our body temperature.

CBSE Class 9 Science Important Questions

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• School Education /

NCERT Solutions Class 9 Science Chapter 1 ‘Matter in Our Surroundings’ (Free PDF) 

• Updated on  
• Apr 13, 2024

We are providing NCERT Solutions Class 9 Science Chapter 1 ‘Matter in Our Surroundings’ to help you navigate through your school exams. You can also download a PDF for important questions and answers for quick revision. Let us get started!     

Download the NCERT Solutions of Class 9 Science Chapter 1 PDF Here!  

Download Solutions of all the Chapters of Class 9 Science : 

NCERT Solutions Class 9 Science Chapter 1 Matter in Our Surroundings 

Here are NCERT Solutions of Class 9 Science Chapter 1 ‘Matter in Our Surroundings’ to the questions in the exercise section of the lesson.     

1. Convert the following temperature to Celsius scale.

(a) 293K                (b) 470K

(a) 293K= (293 – 273)°C = 20°C

(b)  470K= (470 – 273)°C = 197°C

2.Convert the following temperatures to the Kelvin scale.

(a) 25°C                (b) 373°C

(a) 25°C = (25+273)K = 298K

(b) 373°C = (373+273)K = 646K

3. Give reason for the following observations: 

(a) Naphthalene balls disappear with time without leaving any solid.

(b) We can get the smell of perfume while sitting several metres away.

(a) Naphthalene balls, at room temperature, directly go from solid state to gaseous state without changing to liquid state. This is known as sublimation. Hence, they disappear with time without leaving any solid. 

(b) Perfumes are volatile substances which means they change from liquid to gas at room temperature. And gas particles have high kinetic energy, so they spread fast. Hence, even while sitting several meters away, we are able to smell the perfume. 

4. Arrange the following in increasing order of forces of attraction between the particles – water, sugar, oxygen.

Oxygen (gas) < water (liquid) < sugar (solid)

5. What is the physical state of water at –  

(a) 25°C (b) 0°C (c) 100°C?

(a) At 25°C, the water will be liquid at normal room temperature. 

(b) 0°C is the freezing point of water, hence, solid and liquid, both forms will be observed. 

(c) 100°C is the boiling point of water, hence liquid and gaseous, both forms of water will be observed. 

6. Give two reasons to justify –

(a) Water at room temperature is a liquid.

(b) An iron almirah is a solid at room temperature.

(a) The boiling point of water is 100 degrees Celcius which is much more than the normal room temperature. Hence, at room temperature, water exists as a liquid. 

(b) The melting point of metals is much higher than the room temperature. Hence, an iron almirah is solid at room temperature. 

7. Why is ice at 273K more effective in cooling than water at the same temperature?

Solution : At 273 Kelvin, ice will absorb the latent heat to overcome the forces of attraction of the molecules and will turn to water still retaining the same temperature, but water at the same temperature will not absorb excess latent heat from the surroundings. Hence, at 273 Kelvin, ice is more effective in cooling than water. 

8. What produces more severe burns, boiling water or steam?

Solution : Steam will cause more severe burns compared to boiling water because steam will first release the heat that had been consumed during the vaporization while still maintaining the same temperature. 

9. Name A, B, C, D, E and F in the following diagram showing a change in its state.

Solution : 

Credits: NCERT

(A) Solid to Liquid -> Melting (or) fusion (or) liquefaction

(B) Liquid to Gas -> Evaporation (or) vaporization

(C) Gas to liquid -> Condensation

(D) Liquid to Solid -> Solidification

(E) Solid to Gas -> Sublimation

(F) Gas to Solid -> solidification 

Download the NCERT Solutions of Class 9 Science Chapter 1 PDF Here! 

Related Reads : 

Explore Notes of All subjects of CBSE Class 9:

Ans: The first chapter in NCERT Science Class 9 textbook is “Matter in our Surroundings”. 

Ans: Anything or object that occupies space and has mass is considered as matter. 

Ans: Gas is a state of matter in which the molecules are very far apart and have high kinetic energy. 

Follow Leverage Edu for complete study material on CBSE Notes of Class 9 Science . 

Deepansh Gautam

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• CBSE Notes For Class 9
• Class 9 Science Notes
• Chapter 1: Matter In Our Surroundings

Matter In Our Surroundings Class 9 Notes - Chapter 1

Cbse class 9 science notes chapter 1 matter in our surroundings, states of matter.

• Matter can be classified as solid, liquid or gas on the basis of interparticle forces and the arrangement of particles.
• These three forms of matter are interconvertible by increasing or decreasing pressure and temperature.  For example, ice can be converted from solid to a liquid by increasing the temperature.

For more information on Matter Around Us, watch the below video

To know more about the States of Matter, visit here .

For more information on the States of Matter, watch the below video

Atomic View of the Three States of Matter

Physical Nature of Matter

• A physical property is an aspect of matter that can be observed or measured without changing its nature or composition.
• It is independent of the amount of matter present.
• Physical properties include appearance, colour, odour, density, texture, melting point, boiling point, solubility, etc.

For more information on Physical Nature of Matter, watch the below video

To know more about the Physical Nature of Matter, visit here .

Characteristics of Particles of Matter

Matter is anything that has mass and occupies space.

• Everything that we can touch, see, hear, taste and also smell is matter.
• It is made up of really tiny particles which cannot be seen through the eye.

For more information on Characteristics of Particles of Matter, watch the below video

The particles of which the matter is comprised influence its state and properties (physical and chemical).

1. Particles of matter have spaces between them

• This characteristic is one of the concepts behind the solubility of a substance in other substances. For example, on dissolving sugar in water, there is no rise in the water level because the particles of sugar get into the interparticle spaces between the water particles.

2.  Particles of matter are always in motion

• Particles of matter show continuous random movements due to the kinetic energy they possess.
• A rise in temperature increases the kinetic energy of the particles, making them move more vigorously.

3.  Particles of matter attract each other In every substance, there is an interparticle force of attraction acting between the particles. To break a substance, we need to overcome this force. The strength of the force differs from one substance to another.

To know more about the Characteristics of Particles of Matter, visit here .

When the particles of matter intermix on their own with each other, the phenomenon is called diffusion . For example, spreading of ink in water.

• During diffusion, the particles occupy the interparticle spaces.
• The rate of diffusion increases with an increase in temperature due to increase in the kinetic energy of the particles.

To know more about Diffusion, visit here .

Can Matter Change Its State?

Effect of change of temperature on the state of matter.

On increasing the temperature, the kinetic energy of the particles of the matter increases, and they begin to vibrate with higher energy. Therefore, the interparticle force of attraction between the particles reduces, and particles get detached from their position and begin to move freely.

• As a result, the state of matter begins to change.
• Solids undergo a phase change to form liquids.
• Similarly, liquids also undergo a phase change to form gases.

To know more about the Changing State of Matter, visit here .

Melting Point

The melting point of a solid is defined as the temperature at which solid melts to become liquid at the atmospheric pressure.

• At the melting point, these two phases, i.e., solid and liquid, are in equilibrium, i.e., at this point, both solid state and liquid state exist simultaneously.

When two atoms collide to create a heavier atom, such as when two hydrogen atoms combine to create one helium atom, this process is known as fusion. This process generates enormous amounts of energy, many times more than fission, and powers the sun. Furthermore, it doesn’t generate radioactive fission products.

The melting point at which ice, a solid, turns to water, a liquid, is 32°F (0°C).

Boiling Point

The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure.

The boiling point for any material is the temperature point at which the material transforms into the gas phase in the liquid phase. This happens at 100 degrees centigrade for water. The Celsius scale was in fact created on the basis of the ice/water melting point and the liquid water/vapor boiling point.

Read more:   Celsius to Kelvin

Latent Heat of Fusion

It is the amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.

Latent Heat of Vaporisation

It is the amount of heat energy that is required to change 1 kg of a liquid into gas at atmospheric pressure at its boiling point.

Sublimation

The transition of a substance directly from its solid phase to gaseous phase without changing into the liquid phase (or vice versa) is called sublimation.

Effect of Change in Pressure on the State of Matter

By applying pressure, the interparticle spaces between particles of matter decrease. Thus, by applying pressure and reducing temperature, we can convert a solid to liquid and a liquid to gas.

Flowchart for Inter-Conversion of the Three States of Matter

Evaporation

The phenomenon by which molecules in liquid state undergo a spontaneous transition to the gaseous phase at any temperature below its boiling point is called evaporation.

• For example, the gradual drying of damp clothes is caused by the evaporation of water to water vapour.

For more information on Evaporation, watch the below video

To know more about Evaporation, visit here .

Factors Affecting Evaporation

• Temperature: The rate of evaporation increases with an increase in temperature.
• Surface area: The rate of evaporation increases with an increase in surface area.
• Humidity: The rate of evaporation decreases with an increase in humidity.
• Wind speed: The rate of evaporation increases with an increase in wind speed.

To know more about Factors Affecting Rate of Evaporation, visit here .

Cooling Due to Evaporation

During evaporation, the particles of a liquid absorb energy from the surroundings to overcome the inter-particle forces of attraction and undergo phase change. The absorption of heat from the surrounding makes the surroundings cool.

For example, sweating cools down our body.

Applications of Evaporative Cooling

• To keep water cool, it is kept in earthenware containers. Similar to the pores in cotton fabric, the pores in the earthen pot’s surface area allow for more evaporation.
• To keep our bodies cool, we sweat a lot. Evaporation is what transpiration ultimately is. Our body’s water evaporates, using energy in the process and lowering our body temperature as a result.
• We dress in cotton during the summer. Since cotton is a powerful water absorbent, it allows more perspiration to come into touch with the air, promoting more evaporation. We have a cooling effect when wearing cotton clothing because of this.
• NCERT Solutions for Class 9 Science Chapter 1 Matter In Our Surroundings
• Important Questions for Class 9 Science Chapter 1 –Matter In Our Surroundings
• NCERT Exemplar Class 9 Science Solutions for Chapter 1 – Matter In Our Surroundings
• Matter In Our Surroundings
• Maths Notes For Class 9
• CBSE Class 9 Social Science Notes

Frequently Asked Questions on CBSE Class 9 Biology Notes Chapter 1 Matter in Our Surroundings

What is the ‘latent heat of fusion’.

The latent heat of fusion is the enthalpy change of any amount of substance when it melts.

What does ‘sublimation critical point’ mean?

The sublimation critical point refers to the maximum or minimum temperature and pressure beyond which the state of the matter cannot be changed.

What does ‘interconversion of matter’ mean?

Interconversion of matter refers to the change from one state to another. It is a process by which matter changes from one state to another and back to its original state without any change in its chemical composition.

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NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings

• Last modified on: 3 years ago
• Reading Time: 28 Minutes

Here we have given NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings.

INTEXT Questions

Question 1. Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume. Solution: Chair, Sir, smell, almonds, cold drink and smell of perfume.

Question 2. Give reasons for the following observation: The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food, you have to go close. Solution: This happens because rate of diffusion of gas increases with increase in temperature. In case of hot food, diffusion of smell is faster whereas in case of cold food, diffusion is slower.

Question 3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show? Solution: The particles of water are held together by forces of attraction. As these forces are not strong, the diver is able to cut through water in a swimming pool. This observation shows that particles of matter attract one another.

Question 4. What are the characteristics of the particles of matter? Solution: The characteristics of the particles of matter are as follows : (a) Matter consists of tiny particles which cannot be seen by an individual with naked eye. (b) The particles of matter have spaces between them. (c) The particles of matter attract each other due to inter molecular forces of attraction. The forces of attraction are maximum in solids and minimum in gases. Liquids have inter molecular forces in between solids and gases. (d) The particles of matter are not stationary but are continuously moving. (e) The inter molecular forces decrease with the increase in inter molecular spaces and vice-versa. (f) Kinetic energy of the molecules increases with the rise in temperature.

Question 5. The mass per unit volume of a substance is called density, (density = mass/volume) Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton and iron. Solution: The increasing order of density is air < exhaust from chimney < cotton < water < honey < chalk < iron.

Question 6. (a) Tabulate the differences in the characteristics of states of matter. (b) Comment upon the following : rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density Solution: (a) The main characteristics of states of matter :

(b) (i) Rigidity : It is the property which helps a substance to retain its shape when force is applied to it. Splids are rigid while gases and liquids are not. (ii) Compressibility : The property due to which the particles of matter can be compressed or reduced in volume by applying force or pressure. Gases are highly compressible. (iii) Fluidity: It is the tendency of a substance to flow. Liquids and gases possess fluidity while solids are rigid. (iv) Filling a gas container : The molecules of a gas move in all directions and due to negligible inter particle force of attraction can fill the container. (v) Shape: Solids have definite shape whereas liquids take the shape of the container in which they are placed and gases do not have any shape. (vi) Kinetic energy: It is the energy possessed by the particles due to their motion. The particles of a gas have maximum kinetic energy due to free motion of gas particles in all directions. Solids have minimum kinetic energy due to least movement of particles. (vii) Density : Density is the mass of a substance per unit volume. Solids have highest density since their molecules are closely packed.

Question 7. Give reasons: (a) A gas fills completely the vessel in which it is kept. (b) A gas exerts pressure on the walls of the container. (c) A wooden table should be called a solid. (d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert. Solution: (a) The particles of a gas are constantly moving in all the directions with different speeds. Therefore, they do not have a fixed volume and hence completely fill the vessel in which they are kept. (b) The molecules of a gas are free to move randomly in all directions. During their motion, they collide with one another and also with the walls of the container. The constant bombardment of the molecules on the walls of the container exerts a steady force. The force acting per unit area on the walls of the container is called pressure. Thus, gases exert pressure. (c) A wooden table is called solid because it has a definite mass, volume and shape. (d) In air, there is lot of empty space between the molecules and the forces between the particles are almost negligible. Hence, we can move our hand in air. However, we cannot move our hand in a solid block because there are strong forces of attractions between particles in a solid and there is no empty space between them.

Question 8. Liquids generally have lower density  as compared to solids. But you must have observed that ice floats on water. Find out why? Solution: When water freezes to form ice, some empty spaces are created. As a result, volume increases for the same mass of water. In other words, mass per unit volume or density of ice is lower than that of water and hence, ice r floats over water.

Question 9. Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K. Solution: (a) Temperature in °C = Temperature in kelvin – 273 = 300 – 273 = 27°C (b) Temperature in °C = 573 – 273 = 300°C

Question 10. What is the physical state of water at: (a) 250°C (b) 100°C? Solution: (a) Physical state of water at 250°C is gaseous state because the boiling point of water is 100°C. Therefore at a temperature higher than its boiling point, it exists as gas. (b) At 100°C both liquid and gaseous states are present. These are in a state of equilibrium. So, at 100°C both liquid water and vapours are present.

Question 11. For any substance, why does the temperature remain constant during the change of state? Solution: The temperature remains constant during the change of state because the heat supplied during the change is used up in overcoming the inter molecular forces between the particles of the state.

Question 12. Suggest a method to liquefy atmospheric gases. Solution: In order to liquefy a gas, the constituent particles or molecules have to be brought closer. The atmospheric gases can be liquefied either by increasing pressure or by decreasing temperature.

Question 13. Why does a desert cooler cool better on a hot dry day? Solution: The cooling in a desert cooler is caused by the evaporation of water. A desert cooler cools better on a hot and dry day because the higher temperature on a hot’ day and the dryness of air (low humidity of air increases the rate of evaporation of water). Hence, due to increased rate of evaporation of water, a desert cooler cools better on a hot and dry day.

Question 14. HOW does the water kept in an earthen pot (matka) become cool during summer? Solution: An earthen pot (matka) has many small pores. Water seeps out through them and evaporates from the surface of the pot. The energy needed for evaporation is taken from the water kept in the earthen pot. As a result, water kept in earthen pot becomes cool.

Question 15. Why does our palm feel cold when we put some acetone or petrol or perfume on it? Solution: Both acetone and perfume are low boiling liquids. When they are poured on the palm, they evaporate readily and for this change of state they take the energy from the palm and we get a cooling sensation.

Question 16. Why are we able to sip hot tea or milk faster from a saucer rather than a cup? Solution: We are able to sip hot tea faster from a saucer rather than a cup because a saucer has a greater surface area. As a result, rate of evaporation increases.

Question 17. What type of clothes should we wear in summer? Solution: We should wear cotton clothes in summer. During summer, we perspire more because of the mechanism of our body which keeps us cool. Cotton, being a good absorber of water helps in absorbing the sweat and exposing it to the atmosphere for easy evaporation.

NCERT Exercises

Question 1. Convert the following temperatures to Celsius scale: (a) 293 K (b) 470 K Solution: (a) We know that, temperature in °C = K – 273 = 293 – 273 = 20°C (b) °C = K – 273 = 470 – 273 = 197°C

Question 2. Convert the following temperatures to the Kelvin scale: (a) 25°C (b) 373°C Solution: (a) We know that temperature in K = °C + 273 K = 25° + 273 = 298 K (b) K = °C + 273 = 373 + 273 = 646 K

Question 3. Give reasons for the following observations: (a) Naphthalene balls disappear with time without leaving any solid. (b) We can get the smell of perfume sitting several metres away. Solution: (a) Naphthalene balls disappear with time without leaving any solid because they undergo sublimation i.e they directly change into vapours without passing through the liquid state. (b) We can get the smell of perfume sitting several metres away due to diffusion. The perfumes contain solvent which carries pleasant smelling vapours. They diffuse quite fast and can reach a person sitting several metres away.

Question 4. Arrange the following substances in increasing order of forces of attraction between the particles – water, sugar, oxygen. Solution: The forces of attraction are the strongest in solids, followed by liquids and the weakest in gases. Oxygen is a gas, water is a liquid and sugar is a crystalline solid. So, the increasing order of forces of attraction is oxygen < water < sugar.

Question 5. What is the physical state of water at (a) 25°C (b) 0°C (c) 100°C? Solution: (a) At 25°C, the physical state of water is a liquid. _ (b) At 0°C, the physical state of water can be either a solid or a liquid. (c) At 100°C, the physical state of water can be either a liquid or a gas (steam).

Question 6. Give two reasons to justify: (a) water at room temperature is a liquid. (b) an iron almirah is a solid at room temperature. Solution: (a) Water is a liquid at room temperature due to following reasons : (i) Water has fixed volume, but not fixed shape, it takes the shape of the container. (ii) Water can flow easily, hence it is not rigid ‘but a fluid. (b) An iron almirah is a solid’ at room temperature due to following reasons : (i) An almirah has a fixed shape and a fixed volume. (ii) It cannot flow, hence it is rigid.

Question 7. Why is ice at 273 K more effective in cooling than water at the same temperature? Solution: Ice at 273 K melts to form water at 273 K by absorbing heat energy equal to latent heat from the surroundings. Hence ice has less heat energy than water and is more effective in cooling.

Question 8. What produces more severe burns, boiling water or steam? Solution: Steam contains more-heat, in the form of latent heat, than boiling water. So when steam comes in contact with skin it gives out 22.5 × 10 5  joules per’kilogram more “heat than boiling water, so steam causes more severe bums.

NCERT Solutions for Class 9 Science

• Chapter 1 Matter in Our Surroundings
• Chapter 2 Is Matter Around Us Pure
• Chapter 3 Atoms and Molecules
• Chapter 4 Structure of the Atom
• Chapter 5 The Fundamental Unit of Life
• Chapter 6 Tissues
• Chapter 7 Diversity in Living Organisms
• Chapter 8 Motion
• Chapter 9 Force and Laws of Motion
• Chapter 10 Gravitation
• Chapter 11 Work and Energy
• Chapter 12 Sound
• Chapter 13 Why Do We Fall Ill
• Chapter 14 Natural Resources
• Chapter 15 Improvement in Food Resources

We hope the NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings help you. If you have any query regarding NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings, drop a comment below and we will get back to you at the earliest.

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