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Class 8 Science Case Study Question and Answer: CBSE / NCERT Board Class 8 Science Case Study Question prepared by expert Science Teacher. Students can learn Case Based Question / Paragraph Type Question for NCERT Class 8 Science.

There are total 18 chapter Crop Production and Management, Microorganisms: Friend and Foe

, Synthetic Fibres and Plastics, Materials: Metals and Non-Metals, Coal and Petroleum, Combustion and Flame, Conservation of Plants and Animals, Cell – Structure and Functions, Reproduction in Animals, Reaching the Age of Adolescence, Force and Pressure, Friction, Sound, Chemical Effects of Electric Current, Some Natural Phenomena, Light, Stars and the Solar System, Pollution of Air and Water

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CBSE Class 8 Science Case Study Question

• Chapter 1 Crop Production and Management Case Study Question
• Chapter 2 Microorganisms: Friend and Foe Case Study Question
• Chapter 3 Synthetic Fibres and Plastics Case Study Question
• Chapter 4 Materials: Metals and Non-Metals Case Study Question
• Chapter 5 Coal and Petroleum Case Study Question
• Chapter 6 Combustion and Flame Case Study Question
• Chapter 7 Conservation of Plants and Animals Case Study Question
• Chapter 8 Cell – Structure and Functions Case Study Question
• Chapter 9 Reproduction in Animals Case Study Question
• Chapter 10 Reaching the Age of Adolescence Case Study Question
• Chapter 11 Force and Pressure Case Study Question
• Chapter 12 Friction Case Study Question
• Chapter 13 Sound Case Study Question
• Chapter 14 Chemical Effects of Electric Current Case Study Question
• Chapter 15 Some Natural Phenomena Case Study Question
• Chapter 16 Light Case Study Question
• Chapter 17 Stars and the Solar System Case Study Question
• Chapter 18 Pollution of Air and Water Case Study Question

What is Case Study Question?

Ans. At case Study there will one paragraph and on the basis of that concept some question will made. Students have to solve that question.

How many marks will have at case based question?

Most of time 5 questions will made from each case. There will 1 or 2 marks for each question.

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Important Questions for CBSE Class 8 Science Chapter 3 - Coal and Petroleum

• Class 8 Important Question
• Chapter 5: Coal And Petroleum

CBSE Class 8 Science Chapter-3 Important Questions - Free PDF Download

Free PDF download of Important Questions with solutions for CBSE Class 8 Science Chapter 3 - Coal and Petroleum prepared by expert Science teachers from latest edition of CBSE(NCERT) books. Register online for Class 8 Science tuition on Vedantu.com to score more marks in your examination.

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 8 Maths NCERT Solutions to help you to revise complete syllabus and score more marks in your examinations.

Study Important Questions for Class 8 Science Chapter 3 – Coal and Petroleum

Very Short Answer Questions: (1 Marks)

1. When coal burns in air _________ is formed.

A. Carbon Dioxide B. Sulphur Dioxide

C. Carbon Monoxide D. Hydrogen Gas

Ans: A. Carbon Dioxide.

2. Which one of the following is obtained from coal tar? 

A. Petrol B. Coke 

C. Air D. Naphthalene Balls

Ans: D. Naphthalene Balls

3. Which one of the following is NOT a fossil fuel? 

A. Petrol B. Coal 

C. Wood D. Diesel

Ans: C. Wood

4. Which one of the following is NOT a non-renewable energy resource? 

A. Coal B. Petroleum 

C. Solar energy D. Electricity

Ans: C. Solar Energy

5. ___________ is a natural resource. 

A. Car B. Bus 

C. Water D. Parks

Ans: C. Water

6. Which one is least polluting Fuel? 

A. Petrol B. Diesel 

C. CNG D. Kerosene

Ans: C. CNG

7. Coal tar contains about ____________. 

A. 300 Substance B. 400 Substance 

C. 200 Substance D. 100 Substance

Ans: C. 200 Substances

8. Give examples of any two exhaustible resources.

Ans: Coal, petroleum, etc.

9. Give examples of any two inexhaustible resources.

Ans: Sunlight, air, etc

10. Give any two uses of coal.

Ans: Cooking, running rail engines, etc.

11. Name the products of coal.

Ans: Coke, coal tar, coal gas

12. Give any two uses of petroleum.

Ans: Uses of petroleum:

i. It is used to run vehicles.

ii. It is used in petroleum products like Vaseline.

13. Name any two natural gas reserves in India.

Ans: Tripura, Rajasthan, Maharashtra

Short Answer Questions: (3 Marks)

14. What are natural resources? Differentiate between exhaustible and inexhaustible natural resources.

Ans: Resources which we find in our natural environment are called natural resources. Natural resources can be classified into two categories:

15. Define fossil fuels

Ans: Fossil fuels are formed by the constant decomposition of dead and decaying animals and plants under pressure and heat in the earth’s crust. Fossil fuel takes thousands of years to form. Example: Coal, Petroleum etc.

16. What is petroleum? How is it formed?

Ans: Petroleum is a type of exhaustible natural resource. Diesel and petrol are obtained from petroleum. Petroleum is found deep inside water in the sea or oceans. 

Petroleum is formed from dead organisms which are found in water. The bodies of dead organisms settle at the bottom of the ocean and get covered with soil/sand or other aquatic plants and start decaying slowly. Over millions of years, these dead organisms turn into petroleum or natural gas due to the non-availability of proper oxygen, heat and constant high pressure.  

17. What is refining? Why does petroleum require refining?

Ans: The process of separating the various constituents of petroleum at different boiling points is known as refining. Natural petroleum is a crude dark coloured liquid with a very unpleasant smell. It cannot be used in its crude form. Hence, we find petroleum in several different products such as diesel, petrol, wax and use it for various purposes.

18. Name the different constituents of petroleum and write their uses.

19. Why is natural gas a very important fossil fuel?

Ans: Natural gas is important fossil fuel because it mainly constitutes methane and doesn’t produce much pollution. It is a clean gas. Natural gas compressed under high pressure forms CNG which we use in our cars as fuel.

20. State the uses of natural gas.

Ans: Natural gas is used for: 

a. Power generation. 

b. Fuel for transport vehicles. 

c. As a fuel in homes for cooking.

d. Manufacturing of fertilizers and chemicals.

21. Why is natural gas preferred over petrol as a transport fuel?

Ans: Natural gas is preferred over petrol because it is a clean-burning fuel and produces less harmful substances into the air. 

Long Answer Questions: (5 Marks)

22. Explain in detail the products of coal.

Ans: Coal is processed in the industry to get some useful products such as coke, coal tar and coal gas.

(a) Coke: Coke is almost a pure form of carbon. It is dark in colour. It is used for the extraction of metals.

(b) Coal Tar: It is a black liquid with a very unpleasant smell. It is a by-product obtained during the formation of coke. Coal tar is a major constituent during the manufacturing of paints or anti-dandruff shampoos.

(c) Coal Gas: Coal gas is also obtained during the formation of coke. 

23. Why should we use some resources like coal and petroleum in limit?

Ans: Resources like coal and petroleum are from exhausting natural resources. They are formed by the decomposition of dead organisms over millions of years. Their replenishment rate is very slow. Also, this fossil fuel produces carbon dioxide on burning which is very harmful to our environment causing air pollution as well as global warming. Hence, we should use coal and petroleum in limited amounts.

24. Suggest ways in which consumption of fuels can be reduced.

Ans: Petroleum Conservation Research Association (PCRA) advises people on how to save petrol/diesel while driving. This will also help in the reduction of air pollution.

Some of the ways are as follows:

Use more renewable sources of energy such as CNG.

Switch off the engine of the vehicle at traffic lights or in long jams.

Ensure regular maintenance of the vehicle.

We can use bicycles for a small distance.

Importances of Important Questions for CBSE Class 8 Science Chapter 3- Coal and Petroleum

The importance of having a set of important questions for CBSE Class 8 Science Chapter 3, "Coal and Petroleum," cannot be overstated. These questions serve as invaluable tools for students studying this crucial topic. 

Firstly, they offer a structured approach to learning, helping students identify and focus on the key concepts within the chapter. This ensures that they grasp the fundamental principles of the formation, extraction, and uses of coal and petroleum. 

Secondly, by answering these questions, students engage in active learning, which is essential for retention and understanding. Furthermore, important questions aid in exam preparation by providing a clear outline of the topics that are likely to be covered in assessments. 

They enable students to evaluate their knowledge and pinpoint areas that require further study. In essence, important questions enhance the learning experience, making the complex subject of coal and petroleum more accessible and facilitating better academic performance.

Conclusion 

In conclusion, the compilation of important questions for CBSE Class 8 Science Chapter 3, "Coal and Petroleum," holds significant educational value. These questions serve as indispensable aids in the study of this critical subject. They provide a structured approach to learning, enabling students to focus on essential concepts related to the formation, extraction, and uses of coal and petroleum. Moreover, these questions facilitate active learning, reinforcing understanding and retention. As valuable tools for exam preparation, they help students prioritize their study efforts and assess their knowledge effectively. In essence, important questions enrich the learning experience, making the complex topics of coal and petroleum more accessible and contributing to better academic performance.

FAQs on Important Questions for CBSE Class 8 Science Chapter 3 - Coal and Petroleum

Q1. How is energy useful to us?

Ans: Our life is impossible without energy. It is needed in almost every field of our life. Energy is useful for many purposes like: 

To generate electricity and to run vehicles, we need energy from fuels. 

For electrical appliances like refrigerators, TVs, radios, and computers. 

Energy is required at construction sites to build houses and buildings. 

Energy is needed to cook our food and for other domestic use. 

We need energy like petrochemicals for manufacturing plastics, paints, fibres, and cosmetics. 

To run the machines, power supply is needed in all the factories, industries and agricultural devices.

Q2. Why is petrol an exhaustible natural resource, whereas sunlight is not?

Ans: Petrol is a fossil fuel which requires millions of years to form from the decomposition of buried and plants deep down the earth. It is limited in quantity and can be exhausted by human activities. So, petrol is an exhaustible natural resource but sunlight is an inexhaustible and renewable natural resource as it will continue to radiate energy and present in unlimited quantity. Sunlight cannot be exhausted by human activities.

Q3. What are the steps to conserve the resources?

Ans: We all depend on the resources for various purposes but they are limited in nature. It's our responsibility to conserve them for future use. We should all follow the golden rule of conservation - 3 R’s - Reduce, Reuse and Recycle. Electricity devices that consume less energy should be used at home. Cook on low flame. Switch off lights and fans when not in use and save electricity. Use public transport as much as possible. Solar and Tidal energy should be encouraged and developed as they are unlimited in nature. Instead of burning coal or petroleum to generate electricity, dams should be used.

Q4.  Explain the advantages and disadvantages of using petroleum?

Ans: The advantages of using Petroleum are it is easy to extract at a low cost. It can be stored and transported easily over long distances. By using existing technology, spills and leaks can be controlled. It is a high density fuel. It provides a stable energy resource. It is extremely flexible as a raw material in chemical synthesis. The disadvantages are it is limited and non-renewable form of energy. It causes environmental pollution as combustion releases dangerous gases. To learn more about the topic, refer to the Important Questions for CBSE Chapter 3 - Coal and Petroleum of Class 8 Science  provided by Vedantu . These are available on both the website and the App free of cost.

Q5. Explain why the burning of fossil fuels causes air pollution.

Ans: A lot of air pollution is caused due to burning of fossil fuels. For example, gases like carbon dioxide, carbon monoxide, sulphur dioxide, etc are produced when coal is burnt. This may bring undesirable changes in climate due to the increase of the greenhouse effect. When petrol is burnt in automobiles, major air pollutants are produced like carbon monoxide, sulphur dioxide, etc. All these pollutants are harmful to human beings and living organisms. It can cause breathing problems and skin diseases.

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Important Questions Class 8 Science Chapter 3

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Important Questions Class 8 Science Chapter 3 – Synthetic Fibres and Plastics

Science as a subject plays a vital role in a student’s academic life. Class 8 is one of the stepping stones for the students; therefore, learning the basics of Science and comprehending the theory and concepts introduced in the chapters is essential. Studying and practising the subject is important; many students enjoy learning and understanding the Science subject. 

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This chapter includes different topics like synthetic fibres and their meaning, types of synthetic fibres, the characteristics, plastics, various benefits of plastics, use of plastic as a choice, hazards of use of plastic on our environment, and exposure to many other fibres like nylon, rayon, melamine, bakelite, etc. The chapter mainly deals with the type of cloth we utilise daily. These clothes are made up of fabric, so two types of fabric are explained in the chapter. The natural fibre is obtained from plants, and humans synthesise synthetic fibre for different purposes using some chemicals.

 Important topics that are covered in Chapter 3 of Class 8 Science – Synthetic Fibres and Plastics:

• What are synthetic fibres?
• The types of synthetic fibres
• Characteristics of these synthetic fibres
• Plastics as materials of choice
• Plastics and impact on the environment

Extramarks is an online learning platform considered the most preferred educational site by millions of students studying our course materials. For students, we have provided many NCERT oriented study materials such as NCERT chapter notes, CBSE revision notes, CBSE extra questions, CBSE sample papers, etc. 

A few students might face difficulty in understanding the chapters, as they find it difficult to memorise concepts and names in the answers. Therefore, practising questions and answers from Extramarks question bank Important Questions Class 8 Science Chapter 3 will benefit students massively by providing them stepwise solutions to every question.

Science Class 8 Chapter 3 important questions covers all aspects of the chapter and bring a complete set of questions per the latest CBSE syllabus. Our subject matter experts at Extramarks have compiled important questions Class 8 Science Chapter 3 from various reference materials: CBSE past year question papers, CBSE sample paper and NCERT textbook. Students will also get comprehensive solutions for each type of question. Important questions Class 8 Science Chapter 3 includes long answer types, short answer types, and MCQs.

Important Questions Class 8 Science Chapter 3 – With Solutions

You can also find CBSE Class 8 Science Chapter-by-Chapter Important Questions here:

Question 1. Which of the following groups contains all synthetic substances?

• Nylon, Terylene, Wool
• Cotton, Polycot, Rayon
• PVC, Polythene, Bakelite
• Acrylic, Silk, Wool

Answer 1: The correct option is C.

Explanation:  

Polymer is a large molecule with very high molecular mass and repeated structural units called monomers. The process included in the formation of polymer from its distinct monomer is called polymerization. They can be classified as natural, synthetic and semi-synthetic polymers. Synthetic polymers are substances which are man-made, derived from petroleum oils and extensively used in daily life and industry.

• Nylon was the first commercially used successful synthetic thermoplastic polymer.
• Terylene or polyethene terephthalate or polyester is for synthetic fibres.
• A blend of wool and kevlar is the synthetic fibre widely used in body armour, was lighter, cheaper and worked better in damp conditions than kevlar alone. Moreover, wool is extracted from an animal source.
• Cotton is a soft, fluffy staple fibre that grows in a boll, or protective capsule, around the seeds of cotton plants. Cotton is derived from plant sources.
• The fibre is almost pure cellulose. So it is not synthetic.
• Rayon is derived from natural cellulose and cannot be considered synthetic.
• PVC, polyethene, and bakelite are three synthetic polymers.

Question 2. Explain why the following are made of thermosetting plastics.

                     (a) Saucepan handles 

                     (b) Electric plugs/switches/plug boards

Thermosetting plastics:

• These are types of plastics that do not get deformed or softened on heating when moulded once.
• Thermosetting plastics are made up of long cross-linked chains of molecules.
• The main characteristics of these plastics are the poor conductivity of heat and electricity.
• They are made up of very rigid structures.
• The main examples of thermosetting plastics are bakelite and melamine.
• Thermosetting plastics are used in saucepan handles because they do not soften on heating and cannot be bent easily. These plastics, like bakelite, are poor conductors of heat.
• Thermosetting plastics are generally used in electric plugs/switches/plug boards as they are bad conductors of electricity. They do not get moulded. Also, they are hard and strong.
• Bakelite is also a thermosetting plastic that is a poor conductor of heat and electricity. 

Question 3. Write about the importance of synthetic polymers in our life.​

Synthetic polymers are substances that are man-made, derived from petroleum oils and extensively used in daily life as well as industry. Synthetic fibres are cheap and thus are feasible for everyone.

Various synthetic polymers are used in our daily life. Some of the major uses of these polymers are as follows-

• Nylon is used for making ropes for rock climbing, fishing nets, raincoats, parachutes and tyre cords, etc., due to its excellent elasticity and high strength.
• Acrylic is used for sweaters, tracksuits, linings for boots and gloves and In furnishing fabrics and various carpets because of its similarity with many natural fibres.
• Terylene- It is used in the textile industry for making clothes like sarees, tapestry and dress material. It is mixed with natural fibre like cotton and wool to make a vast variety of clothes.
• Rayon- It is used for making carpets, tyre cords, and surgical dressings in the textile industry.
• Plastics- It is used to store food items, water, milk, pickles, dry food, etc. Plastic containers seem to be the most convenient. This broad usage is because of its lightweight, low price, good strength and easy handling compared to metals. Plastics are used in cars, air crafts and spacecraft.

Question 4. Despite being very useful, we are advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?

Plastic is a non-biodegradable material, and as such, it causes land pollution. At the same time, burning materials like plastic as garbage causes serious air pollution.

Improper disposal of plastics causes several problems. Some of these are:

• The littering of plastics in open and public spaces creates unhygienic conditions, as it acts as a major breeding ground for insects and mosquitoes that cause diseases like malaria and dengue.
• Plastics do not undergo degradation; thus, they stay in the soil for many years, which affects soil fertility and degrades the soil quality.
• Plastic blocks the pipes if it enters the drainage and sewerage system and the drains causing water logging.
• Plastic items often find their way to the river and other water bodies, which fish and seabirds then swallow, and other marine species, thus leading to suffocation and death.

Some ways to limit its consumption are:

• Paper bags are highly recommended to use instead of plastics.
• Reuse if it is possible to reduce plastic consumption, thereby decreasing its consumption.
• Recycling of plastic. It requires the plastic to be collected, sorted, chopped, melted and remoulded.
• Do not burn the plastic as it causes the release of carbon monoxide, which is a very harmful gas-causing cancer.

Question 5. The most suitable material for the preparation of handles of cooking utensils is _______.

Answer 5: The correct option is D .

Explanation:

Polythene is not used for the preparation of handles of cooking utensils since it gets soft on heating. Therefore, this option gets eliminated.

PVC is polyvinyl chloride, a thermoplastic, and it gets melted on heating, due to which it is not used for the preparation of cooking utensils. Thus, this option gets eliminated.

Option (D) is correct: For making the handles of cooking utensils, the most suitable material is bakelite. Bakelite is a very poor conductor of heat and does not become soft on getting heated, so it is the preferred material for making the handles of many cooking utensils. Bakelite is the commercial name kept for the polymer material obtained by the polymerization of phenol and formaldehyde.

Question 6. ‘Manufacturing synthetic fibres are actually helping conservation of forest’. Comment.

Synthetic fibres are made from synthesised polymers of small molecules. The compounds used to make these fibres come from various raw materials such as petroleum-based chemicals or petrochemicals. These materials are also polymerized into a chemical that bonds two adjacent carbon atoms. Differing chemical compounds are mainly used to produce different types of synthetic fibres. Synthetic fibres are made only from natural gas polymers and petroleum by-products.

Manufacturing synthetic fibres are actually helping the conservation of forests. Synthetic fibres are man-made fibres, and they are also manufactured from petrochemicals. If we use these synthetic fibres, we do not require to cut trees down and hence help in the conservation of forests.

Since synthetic fibres are mainly obtained from petrochemicals, they have excellently substituted the use of different natural fibres like cotton, wool, silk and jute, which are obtained from animals and plants. As a result, plants need not be cut to produce fibres.

Synthetic fibres are considered more durable than most natural fibres and readily pick up different dyes. In addition, many synthetic fibres offer consumer-friendly functions like stretching, waterproofing and also stain resistant. Sunlight, moisture, and oils produced by the human skin cause all fibres to break down easily and wear away.

Plant fibres are obtained from different parts of plants, such as the seeds (cotton, milkweed, kapok), stems (jute, hemp, flax, ramie, kenaf, nettle, kenaf, bamboo), and leaves (manila, sisal, abaca), fruit (coir) and various other grass fibres. Fibres from these plants are considered to be renewable and biodegradable.

The manufacturing of synthetic fibres aids forest conservation since natural fibres need the extraction of raw materials from plants, which necessitates the falling of many trees. This proves to be very beneficial in forest conservation.

 Some synthetic fibres are listed below.

Advantages of Synthetic Fibres

• Synthetic fibres are extremely durable and do not wrinkle easily.
• They are elastic and are easily stretched out.
• They are very strong and can sustain a heavy load.
• They are soft and hence used in clothing materials.
• They are cheaper than natural fibres.

Question 7. ‘Avoid plastics as far as possible’. Comment on this advice.

Plastic manufacturing involves the addition of potentially hazardous compounds like stabilisers or colourants. Many of them are not even been subjected to environmental risk assessments. Therefore their influence and impact on human health and the environment are unknown.

Most plastics are non-biodegradable; once landfilled, they may take a long and elaborate time to decompose. With an increase in the number of plastic products, especially plastic packaging, and them being discarded immediately and quickly after purchase, the amount of landfill space required for plastic waste is becoming one of the major concerns.

Cheap production and easy availability make plastic very useful. Still, it has many shortfalls, and its harmful effects are a cause of huge concern for us to save our earth and ourselves. Its few disadvantages are listed below:

• The natural decomposition of plastic can last from 400-1000 years.
• Plastics are non-biodegradable substances that take several years to decompose. Since plastic does not decompose, it is accumulating and causes environmental pollution.
• Plastic materials clog waterways, oceans, seas, lakes etc. 1 in 3 species of marine mammals have been found entangled in marine litter. 
• They cannot be burnt as when burnt, they release poisonous gases into the atmosphere, which cause air pollution.
• Plastic causes many fire hazards. 
• Many animals eat plastic materials and eventually die. Over 90% of all seabirds have plastic pieces in their stomachs. Animals like cows swallow plastic bags thrown in the garbage dump. The swallowing of such bags chokes their respiratory system and can even cause death.
• Plastic is widely used for packaging. Eating food out of plastic containers may also lead to cancer.
• Plastic bags that are carelessly thrown are responsible for the clogging of drains, leading to several inconveniences.
• The cost of recycling plastic is also very high. 
• Plastic wrappers of eatables are carelessly spilt in picnic spots, which can also lead to pollution.

Hence, we should make sure to avoid the use of plastic as much as possible.

Question 8. Explain why some fibres are called synthetic.

Some fibres are made by humans and are known as synthetic or artificial. These fibres are artificially prepared using various chemicals based on petroleum. These fibres are called synthetic fibres because they are artificially prepared using chemicals. These fibres are not made from natural fibres. These are made of small units that join together to form long chains. Some synthetic fibres are nylon, rayon, acrylic, polyester etc.

Question 9. A bucket made of plastic does not rust like a bucket of iron. Explain.

The word plastic is generally derived from the Greek word, which means capable of being shaped or moulded. Hence plastic has the property to be moulded in any desired shape. Most plastics contain organic polymers. Generally, it forms a continuous chain of carbon atoms and adds oxygen, sulphur or nitrogen. The long chain also consists of many repeat units known as monomers, and polythene is a polymer in which there are several thousand units. Rusting generally acts on the outer surface of iron, due to which the surface becomes dull. The reactive nature of iron can explain this. Iron reacts with the oxygen present in the air and forms oxides, which get corrupted. The conditions necessary for rust are mainly water and oxygen present in the environment. Plastic is a non-reactive metal, and the main condition for rust is that it should react with water and atmospheric oxygen, so plastic does not rust.

Question 10. Describe the following with examples: thermoplastics and thermosetting polymers. 

Answer 10: 

• Thermoplastic

Thermoplastics are those materials that get deformed easily on heating. Hence, they can be reused again and again. They are malleable and also can be easily bent. Some examples of thermoplastics include polyethene and PVC. Thermoplastics are mainly used in the manufacturing process and production of toys and combs.

• Thermosetting plastics

Thermosetting plastics are materials that can be moulded only once and cannot be softened by heating. A thermosetting polymer is a permanent setting polymer as it gets hardened, sets during the moulding process, and cannot be softened again. Some examples of thermosetting plastics are melamine and bakelite. Melamine can resist fire and can tolerate heat; it is used for making floor tiles, kitchenware, and fabrics. Bakelite is known to be a poor conductor of heat and electricity and is used for commercial making electrical switches, handles of various utensils, etc. 

Question 11. Name two natural fibres and sources from which they are obtained​.

Examples of natural fibres include cotton, wool, flax, jute and coir. Fibres are long, thin and flexible strands and are thread-like structures. Fibres that are made by human beings are called man-made or synthetic fibres. At the same time, those fibres made from animals and plants are called natural fibres.

Source of natural fibres

The two major sources of fibres are animals and plants.

• Cotton, flax, coir, jute, rami, etc., are natural fibres from plants.
• The natural fibres of animals include alpaca, cashmere, silk, wool, etc.

Question 12. Give examples which indicate that nylon fibres are very strong.

Synthetic fibres

• Synthetic fibres are man-made fibres made by chemical synthesis in contrast to natural fibres derived from living organisms.
• They are made of small units which form longer chains.
• Nylon is synthetic fibres made up of repeating units of amides.
• Nylons are condensation polymers.
• Nylons are generally made from petroleum that can be melted to form fibres, films or shapes
• It is formed from the reaction of difunctional monomers.
• They are thermoplastic i.e can be softened through heating in nature.

Some examples below demonstrate the strength of nylon fibres.

• Nylon is used in the making of rock climbing ropes and parachutes.
• Seat belts, tyre cords and fishing nets are all nylon.
• Nylon is also used to make sporting equipment such as rackets.

Benefits of Solving Important Questions Class 8 Science Chapter

Science is an important subject that enables students to understand the functioning of the biological world and its importance. Students will see different types of theoretical and practical questions based on the activities we perform in our everyday life. Therefore, having a strong base foundation and knowledge of Science is necessary. Students are advised to understand the main concepts in the chapter. Chapter 3 Class 8 Science important questions are available on our Extramarks website. Students can quickly refer to the important questions and understand the different variety of questions which are likely to appear in the exam. 

These are the benefits of learning Important Questions Class 8 Science Chapter 3: 

• The questions are compiled from reference materials such as CBSE sample papers, NCERT books, and past years’ question papers. 
• These questions provided by Extramarks serve an important purpose in preparation for the examination. The step-wise explanatory answers are presented in easy-to-understand language.
• These important questions are an upcoming source for the Self-Assessment Module (SAM) and any upcoming exam or test.
• The questions focus on covering every aspect of the subject matter and concepts introduced to the students in the chapter with a strong emphasis on the technique of solving questions rather than just plainly providing answers alone. 
• These important questions are created based on the CBSE Curriculum Framework.
• These important questions include all the latest updates and changes in the CBSE Curriculum Framework.
• The questions mentioned in Important Questions Class 8 Science Chapter 3 are collected from various sources to ensure that they are fully authentic in content and free from errors, omissions, ambiguities, etc.
• The questions have also been written strongly emphasising the yearly examination pattern that CBSE provides for their respective class or grade level students.

Extramarks is one of the most trusted websites For lakhs of students. It is mainly popular amongst primary and secondary students. Lakhs of students across India trust our study material and solutions. In addition, students can also refer to other study materials available on our Extramarks website. Students can refer to the links below and access the most relevant resources available at Extramarks: 

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Q.1 Why should we use the fossil fuels economically and wisely?

Marks: 3 Ans

The deposits of fossil fuels are limited. It requires millions of years for the dead organisms to get converted into these fuels. On the other hand, the known reserves of these will last atmost a few hundred years. Moreover, burning of these fuels is a major cause of air pollution. Their use is also linked to global warming. So, we should use the fossil fuels economically and wisely.

Q.2 (i) What are petrochemicals?

(ii) Why petroleum is called black gold?

Marks: 2 Ans

(i) The useful substances that are obtained from petroleum and natural gas are called petrochemicals.

(ii) Due to great commercial importance of petroleum, it is called black gold.

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Cbse class 8 science important questions, chapter 1 - crop production and management.

Chapter 2 - Microorganisms : Friend and Foe

Chapter 4 - materials : metals and non-metals, chapter 5 - coal and petroleum, chapter 6 - combustion and flame, chapter 7 - conservation of plants and animals, chapter 8 - cell - structure and functions, chapter 9 - reproduction in animals, chapter 10 - reaching the age of adolescence, chapter 11 - force and pressure, chapter 12 - friction, chapter 13 - sound, chapter 14 - chemical effects of electric current, chapter 15 - some natural phenomena, chapter 16 - light, chapter 17 - stars and the solar system, chapter 18 - pollution of air and water, faqs (frequently asked questions), 1. what are the important questions in chapter 3 of science for class 8.

From the examination perspective, Chapter 3 of the Science textbook for Class 8 is important. By practising the Important Questions Class 8 Science Chapter 3, students can better comprehend the concepts taught in the chapter. It is important to comprehend the topics and concepts presented in the chapter for a better and clear understanding. All important questions are chosen based on question papers gathered from several schools from the previous year. This helps us provide more authentic and likely questions for students to prepare well for their examinations.

2. What are synthetic fibres, according to Chapter 3 of Class 8 Science?

The various synthetic fibres are:

Rayon: Rayon is processed from wood pulp. Rayon is very similar to silk and may be dyed in various colours. It is also a cheap alternative to silk. 

Nylon: The first commercially used produced synthetic fibre is nylon. Nylon is processed from coal, air and water. Nylon is also extremely durable and appears like silk. 

Polyester: It is one of the most popular and used forms of synthetic fibres. It is created using repeating units of ester.

Acrylic: Acrylic is known as artificial wool. Acrylic is a fibre that shows a close resemblance to wool.

3. What are the key topics covered in Class 8 Chapter 3 Science?

Chapter 3 of Class 8 Science mainly deals with the concept of synthetic fibres. The clothes that we wear daily are made of fabrics. Various fabrics are made of fibres obtained from different natural and artificial sources. Wool, silk, and cotton are some examples of natural fibres. In Class 8 of Science Chapter 3, the various types of synthetic fibres and their characteristics are mentioned. These are called synthetic because they are artificially prepared with the use of chemicals. This chapter also covers topics around a few examples of synthetic fibres such as nylon, rayon, acrylic, polyester etc. To know in detail about Class 8 Chapter 3 Science basics, you can refer to Important Questions Class 8 Science Chapter 3 available on the Extramarks website. After referring to the step-wise solutions and key points provided in Class 8 Science Chapter 3 important questions, you will surely be able to understand your concepts easily and clearly.

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Case Study Questions Class 8 Science Reaching the age of adolescence

Case study questions class 8 science chapter 10 reaching the age of adolescence.

CBSE Class 8 Case Study Questions Science Reaching the age of adolescence. Important Case Study Questions for Class 8 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Reaching the age of adolescence.

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

CBSE Case Study Questions Class 8 Science Reaching the age of adolescence

Case study 1.

Changes at Puberty: Increase in HeightThe most conspicuous change duringpuberty is the sudden increase inheight. At this time the long bones, thatis, the bones of the arms and the legselongate and make a person tall.Initially, girls grow faster than boysbut by about 18 years of age, both reachtheir maximum height. The rate ofgrowth in height varies in differentindividuals. Some may grow suddenlyat puberty and then slow down, whileothers may grow gradually.There is no need for Paheli to worry.All parts of the body do not grow at thesame rate. Sometimes the arms and legsor hands and feet of adolescents lookoversized and out of proportion with thebody. But soon the other parts catchup and result in a proportionate body. You must have noticed that heightof an individual is more or less similarto that of some family member. This isbecause height depends on the genesinherited from parents. It is, however,very important to eat the right kind offood during these growing years. Thishelps the bones, muscles and otherparts of the body get adequate nourishment for growth. You will find nutritional needs of adolescentsdiscussed later in the lesson.Change in Body Shape: Have you noticed that boys in your classhave broader shoulders and wider cheststhan boys in junior classes? This isbecause they have entered the age ofpuberty when shoulders generallybroaden as a result of growth. In girls,the region below the waist becomeswider.In boys, the muscles of the body grow more prominently than in the girls.Thus, changes occurring in adolescent boys and girls are different.Voice Change: Did you notice that sometimes the voiceof some of the boys in your class cracks?At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice box in boys canbe seen as a protruding part of the throatcalled Adam’s apple. In girls,the larynx is hardly visible from theoutside because of its small size.Generally, girls have a high-pitched voice, whereas boys have a deep voice. Inadolescent boys, sometimes, the musclesof the growing voice box go out of controland the voice becomes hoarse. This statemay remain for a few days or weeks afterwhich the voice becomes normal.Increased Activity of Sweat andSebaceous Glands:During puberty the secretion of sweatglands and sebaceous glands (oil glands)increases. Many young people get acneand pimples on the face at this timebecause of the increased activity of theseglands in the skin.Development of Sex Organs: At puberty, malesex organs like the testes and penisdevelop completely. The testes alsobegin to produce sperms. In girls, theovaries enlarge and eggs begin tomature. Also, ovaries start releasingmature eggs.Reaching Mental, Intellectual andEmotional MaturityAdolescence is also a period of changein a person’s way of thinking.Adolescents are more independent thanbefore and are also self-conscious.Intellectual development takes place andthey tend to spend considerable timethinking. In fact, it is often the time inone’s life when the brain has thegreatest capacity for learning.Sometimes, however, an adolescent mayfeel insecure while trying to adjust tothe changes in the body and mind. Butas adolescent learners, you should knowthat there is no reason to feel insecure.These changes are a natural part ofgrowing up.

Que. 1) The protruding part of the throat usually seen in boys that is responsible for deep voice is known as?

(b) Swollen lymph

(c) Adam’s apple

(d) Thyroid

Que. 2) Which of the following is a change in body shape usually observed in girls?

(a) Broader shoulder

(b) Increased muscle growth

(c) Deep voice

(d) Region below waist wider

Que. 3) During the puberty ……………………………………………………………………………….. starts releasing mature eggs in girls.

(a) Ovaries

(c) Oviduct

Que. 4) Describe the development of secondary sex organs in males.

Que. 5) Why do we observe acne or pimples on the face of young people at the age of adolescence?

Que. 1) (c) Adam’s apple

Que. 2) (d) Region below waist wider

Que. 3) (a) Ovaries

Que. 4) Answer: In males, sex organs like testes and penis develop completely at puberty. The testes begin to produce sperms.

Que. 5) Answer: During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases. Pimples are seen due to increased activity of these glands.

Case study 2

Secondary Sexual: CharactersYou have learnt in Chapter 9, thattestes and ovaries are the reproductiveorgans. They produce the gametes,that is, sperms and ova. In girls,breasts begin to develop at pubertyand boys begin to grow facial hair, thatis, moustaches and beard. As thesefeatures help to distinguish the malefrom the female, they are calledsecondary sexual characters. Boysalso develop hair on their chest. Inboth, boys and girls, hair grows underthe arms and in the region above thethighs or the pubic region.The changes which occur atadolescencearecontrolledbyhormones. Hormones are chemicalsubstances. These are secretions fromendocrine glands, or endocrine system.The male hormone or testosteronebegins to be released by the testes atthe onset of puberty. This causeschanges in boys about which you havejust learnt, for example, the growth offacial hair. Once puberty is reached ingirls, ovaries begin to produce the femalehormone or estrogen which makes thebreasts develop. Milk secreting glandsor mammary glands develop inside thebreasts. The production of thesehormones is under the control ofanother hormone secreted from anendocrine gland called pituitary gland.Role of Hormones inInitiating ReproductiveFunctionEndocrine glands release hormonesinto the bloodstream to reach aparticular body part called target site.The target site responds to thehormone. There are many endocrineglands or ductless glands in the body.The testes and ovaries secrete sexhormones. You have just learnt thatthese hormones are responsible for themale and female secondary sexualcharacters. Further, the sex hormonesare under the control of hormones fromthe pituitary gland. Thepituitary secretes many hormones, oneof which makes ova mature in theovaries and sperms form in the testes.

Que. 1) Sex hormones are under the control of hormones from the ………………………………………………………………………………….. gland.

(a) Adrenal

(b) Pituitary

(c) Thyroid

Que. 2) Which among the following is the example of a major male sex hormone?

(a) Testosterone

(b) Estrogen

(c) Prolactin

(d) Follicle stimulating hormon

Que. 3) The endocrine gland is generally also known as ……………………………………………………………………………………… .

(a) Superficial glands

(b) Doubtful glands

(c) Funny glands

(d) Ductless glands

Que. 4) Define the term “Hormone”.

Que. 5) Name some of the secondary sexual characters observed in girls.

Que. 1) (b) Pituitary

Que. 2) (a) Testosterone

Que. 3) (d) Ductless glands

Que. 4) Answer: Hormones are chemical substances which are secreted from endocrine gland or endocrine system.

Que. 5) Answer: Some of the secondary sexual characters seen in girls include development of breast, hair growth under the arm and pubic region, mammary gland develops inside the breast.

Case study 3

Reproductive Phase of Life in Humans: Adolescents become capable of reproduction when their testes and ovaries begin to produce gametes. Thecapacity for maturation and production of gametes lasts for a much longer timein males than in females. In females, the reproductive phase of life begins at puberty (10 to 12 years of age) and generally lasts till the age of approximately 45 to 50 years. The ovabegin to mature with the onset of puberty. One ovum matures and isreleased by one of the ovaries once inabout 28 to 30 days. During thisperiod, the wall of the uterus be comes thick so as to receive the egg, in caseit is fertilised and begins to develop. This results in pregnancy. If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation. Menstruation occurs once in about 28 to 30 days. The first menstrual flow begins at puberty and is termed menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termedmeno pause. Initially, menstrual cycle may be irregular. It takes some time to become regular. Menstrual cycle is controlled by hormones. The cycle includes the maturation of the egg, its release, thickening of uterine wall and its breakdown if pregnancy does not occur. In case the egg is fertilised it begins to divide and then gets embedded in the uterus for further development as you have learnt inChapter 9How is the Sex of the Baby Determined? Inside the fertilised egg or zygote is the instruction for determining the sex of the baby. This instruction is present inthe thread-like structures, called chromosomes in the fertilised egg.RecallfromChapter8,thatchromosomes are present inside the nucleus of every cell. All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes(egg and sperm) have only one set of chromosomes. The unfertilised egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome. See Fig. 10.4. When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child. Now you know that the sex chromosomes of the father determine the sex of an unborn baby. The belief that the mother is responsible for the sex of her baby is completely wrong and to blame her for this is totally unjustified.

Que. 1) The first menstrual flow begins at puberty and is termed as ………………………………………………………………………………………. .

(a) Menopause

(b) Premenstrual syndrome

(d) Menarche

Que. 2) If a baby has XY chromosomes in its nucleus, then the sex of the baby is?

(c) Both (a) and (b)

(d) None of the above

Que. 3) Which among the following is NOT an event of menstruation in female?

(a) Thickening of uterus wall

(b) Fertilisation of ovum and sperm

(c) Release of matured ovum

(d) Shedding of blood vessels and ovum

Que. 4) Explain in detail the process of menstruation.

Que. 5) Name the possible sex chromosomes present in the male and female gametes.

Que. 1) (d) Menarche

Que. 2) (b) Male

Que. 3) (b) Fertilisation of ovum and sperm

Que. 4)Answer: In about 28-30 days, one ovum maturesand is released from the ovary. Walls of the uterus are thickened to receive the ovum. If fertilisation of that ovum does not occur, the released ovum along with the thickened lining and its blood vessels are shed off causing bleeding.

Que. 5) Answer: Sex chromosomes present in ovum (female gamete) is always X chromosome. The sperms (male gamete) are of two kinds: one kind has X chromosome and the other kind has Y chromosome.

Case study 4

Hormones other than Sex Hormones: The hormones secreted by the pituitary stimulate testes and ovaries to produce their hormones. You have already learnt that the pituitary gland is an endocrine gland.It is attached to the brain.Apart from the pituitary, the testesand the ovaries, there are otherendocrine glands in the body such as thyroid, pancreas and adrenals. Boojho and Paheli had once visitedtheir aunt who was a doctor and remembered that a boy named Kaka hada very big and bulging throat. Their aunt had told them that Kaka was sufferingfrom ‘goitre’, a disease of the thyroid gland. Kaka’s thyroid gland was notproducing the hormone thyroxine. Their aunt also told them that theiruncle was suffering from ‘diabetes’ because his pancreas was not producing the hormone insulin in sufficient quantities. Boojho and Paheli thenasked their aunt about the adrenal glands, which are also shown in the chart hung on the wall of her clinic. Theaunt told them that adrenal glands secrete hormones which maintain thecorrect salt balance in the blood. Adrenals also produce the hormone adrenalin. It helps the body to adjustto stress when one is very angry, embarrassed or worried. Thyroid and adrenals secrete their hormones when they receive orders from the pituitary through its hormones. Pituitary also secretes growth hormone which is necessary for the normal growth of a person. Role of Hormones in Completing the LifeHistory of Insects and Frogs:You have already learnt about the lifehistory of the silk moth and the frog. The caterpillar has to pass throughvarious stages to become an adult moth. Recall from Class VII the stages of thelife history of the silk moth. Similarly, the tadpole passes through certain stages to become a frog (Chapter 9).This change from larva to adult iscalled metamorphosis (Fig. 9.10).Metamorphosis in insects is controlled by insect hormones. In a frog, it iscontrolled by thyroxine, the hormone produced by thyroid. Thyroxine production requires the presence ofiodine in water. If the water in whichthe tadpoles are growing does not contain sufficient iodine, the tadpoles cannot become adults.

Que. 1) If the thyroid gland of a person is not producing thyroxine hormone, he/she is suffering from ………………………………………………………………………………. .

(c) Chicken pox

(d) Diabetes

Que. 2) Metamorphosis in frog is controlled by which of the following hormones?

(a) Insulin

(b) Testosterone

(c) Estrogen

(d) Thyroxine

Que. 3) In a person suffering from Diabetes, the pancreas does not produce …………………………………………………………………………………….. hormone in sufficient quantity.

(a) Adrenalin

(b) Thyroxine

(c) Insulin

(d) Melatonin

Que. 4) Explain the role of adrenal glands.

Que. 5) Name some of the endocrine glands in the human body.

Que. 1) (a) Goitre

Que. 2) (d) Thyroxine

Que. 3) (c) Insulin

Que. 4) Answer: Adrenal glands produce hormone adrenalin, which helps the body to adjust to stress when the person is angry, embarrassed or worried.

Que. 5) Answer:Some of the endocrine glands include: Thyroid, pancreas, adrenal, testes, ovary and pituitary gland.

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Synthetic Fibres and Plastics Class 8 Science Extra Questions and Answers

Synthetic Fibres and Plastics Class 8 Science Chapter 3 Extra Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 8 Science Book. CBSE Class 8 Science Chapter 3 Synthetic Fibres and Plastics Extra Questions will help you to properly understand a particular concept of the chapter.

Class 8 Science Chapter 3 Synthetic Fibres and Plastics Extra Questions

Very short answer type question.

Question 1: Name the plastic whose sheets are used for packing liquids.

Answer: Polythene

Question 2: Name one naturally occurring polymer.

Answer: Cellulose

Question 3: Name the fibre used for making parachutes and ropes for rock climbing.

Answer: Nylon

Question 4: Which synthetic fiber is known as artificial silk?

Answer: Rayon fiber is known as artificial silk.

Question 5: Which is the first fully synthetic fibre?

Answer: Nylon is the first fully synthetic fibre.

Question 6: Write one disadvantage of synthetic fibre.

Answer: Synthetic fibres melt on heating.

Question 7: What are esters?

Answer: Esters are the chemicals which give fruits their smell.

Question 8: What are the 4 R in waste management? Or What are the 4 R’s principles of plastic?

Answer: 4 R principles mean Reduce, Reuse, Recycle and Recover.

Question 9: What are the advantages of nylon?

Answer: Nylon fibre is strong, elastic and light. It is lustrous and easy to wash.

Question 10: Write uses of bakelite.

Answer: It is used for making electrical switches, handles of various utensils, etc.

Question 11: Write uses of melamine.

Answer: It is used for making floor tiles, kitchenware and fabrics which resist fire.

Question 12: How is rayon different from synthetic fibres?

Answer: Rayon is different from synthetic fibres because it is obtained from a natural source, wood pulp.

Question 13: Give examples which indicate that nylon fibres are very strong.

Answer: Nylon fibres are very strong as it is used to make parachutes and ropes for rock climbing.

Question 14: What is polythene?

Answer: Polythene (Poly + ethene) is a type of plastic that is used for making commonly used polythene bags.

Question 15:  Is plastic bag non-biodegradable? Why?

Answer: Plastic bag is non-biodegradable because it takes several years to degenerate.

Question 16:  Can we store jams and pickles in plastic containers? Give reason.

Answer: We can store jams and pickles in plastic containers because plastics do not react with water and air and do not get corroded easily.

Question 17: Do all plastics have same type of arrangement of units?

Answer: All plastics do not have the same type of arrangement of units. In some it is linear, whereas in others it is cross-linked.

Question 18:  Why nylon is called fully synthetic fibre?

Answer: Nylon is called fully synthetic fibre because it is prepared from coal, water and air.

Question 19:  What is polyester?

Answer: Polyester (Poly+ ester) is actually made up of the repeating units of a chemical called an ester.

Question 20:  Write one use of acrylic.

Answer: Acrylic is used as a substitute of natural wool for knitting sweaters, shawls, blankets etc.

Short Answer Type Questions

Question 1:  Why is nylon used for making parachutes and ropes for rock climbing?

Answer: Nylon is used for making parachutes and ropes for rock climbing because nylon fibre is strong and can hold heavy weight.

Question 2:  What is polymer?

Answer: Synthetic fibres and plastics, like natural fibres, are made of very large units called polymers. Polymers are made up of many smaller units.

Question 3: Define petrochemicals.

Answer: All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.

Question 4: Why should we use a cotton carry bag or jute bag while going for shopping?

Answer: We should use cotton or jute bags while going for shopping in order to minimise the use of plastic bags.

Question 5: Why plastic articles are available in all shape and size?

Answer: Plastic articles are available in all possible shapes and sizes because plastic is easily mouldable i.e. can be shaped in any form.

Question 6:  Why is Teflon used for nonstick coating on cookware? Or Which material is used for coating non-stick kitchen wares and why?

Answer: Teflon is used for nonstick coating on cookwares because it is a special plastic on which oil and water do not stick.

Question 7: Explain why plastic containers are favoured for storing food.

Answer: Plastic containers are favoured for storing food because of their light weight, lower price, good strength and easy handling.

Question 8:  What is PET? Write its uses.

Answer: PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Question 9: Give the composition of Polycot and Polywool.

Answer: Polycot is a mixture of polyester and cotton.

Polywool is a mixture of polyester and wool.

Question 10: “Tin, aluminium and other metal can are considered non-biodegradable.” Give reason.

Answer: Tin, aluminium and other metal can are considered non-biodegradable because they approximately take 100 to 500 years to degenerate.

Question 11: Give two uses of rayon.

• It is mixed with cotton to make bed sheets.
• It is mixed with wool to make carpets.

Question 12: Suggest some ways in which we can contribute towards reducing the use of plastic materials?

Answer: Ways to reduce use of plastic materials are

• Avoid the use of plastics as far as possible.
• Make use of bags made of cotton or jute when you go for shopping.

Question 13: Give examples to show that plastics are noncorrosive in nature. Or Why are the chemicals in the laboratory stored in plastic containers? Or Why are plastic containers used to store chemicals in labs?

Answer: Plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.

Question 14: What type of cookware is used in microwave oven and why?

Answer: Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel.

Question 15: How is plastic useful in healthcare industry?

Answer: Plastics find extensive use in the health-care industry. Some examples of their use are the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.

Question 16: Why is melamine used for making floor tiles, kitchenware and fabrics which resist fire?

Answer: Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.

Question 17: Why electrical wires have plastic covering, and handles of screw drivers are made of plastic?

Ans. Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic.

Question 18: Why should recycled plastic not be used for the storage of food? Or Why is recycled plastic not suitable for storage of food items? Or Can recycled plastics be used in food containers? Why or why not?

Answer: Most of the thermoplastics can be recycled. However, during recycling certain colouring agents are added. This limits its usage especially for storage of food.

Question 19: Why plastic finds such a variety of uses?

Answer: The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

Question 20: Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

Answer: The handle and bristle of a toothbrush should not be made of same material as the handle of the toothbrush should be hard and strong while the bristle should be soft and flexible.

Question 21: List the characteristics of synthetic fibres which make them popular dress materials. Or What are characteristics of synthetic Fibres? Or Mention the general characteristics of synthetic plastics.

Answer: Synthetic fibres possess unique characteristics which make them popular dress materials. They dry up quickly, are durable, less expensive, readily available and easy to maintain.

Question 22: Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Answer: Rana should buy cotton shirts for summer because cotton absorbs sweats away from the body and helps eliminate moisture buildup between clothes and skin in order to keep the body dry.

Question 23: How is rayon made? Write two advantages of using rayon. Or What are the advantages of artificial silk over natural silk?

Answer: Rayon is obtained by chemical treatment of wood pulp.

Advantages of Rayon are:

• It is cheaper than silk and can be woven like silk fibres.
• It can also be dyed in a wide variety of colours.

Question 24:  Explain why the following are made of thermosetting plastics.

(a) Saucepan handles

(b) Electric plugs/switches/plug boards

Answer: (a) Saucepan handles are made of thermosetting plastics because it is a poor conductor of heat.

(b) Electric plugs/switches/plug boards are made of thermosetting plastics because it is a poor conductor of heat and electricity.

Long Answer Type Questions

Question 1: Explain why some fibres are called synthetic.

Answer: Some fibres are called synthetic because they are made by human beings by chemical processing.  Such fibre is made up of small units that join together to form long chains. Each small unit is actually a chemical substance.

Question 2: Give three advantages of polythene over natural materials.

Answer: Three advantages of polythene over natural materials are:

• It is light, strong and durable.
• It can be rolled into sheets.
• It does not react with water and air.

Question 4: ‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment

Answer: Natural fibres are obtained from plants and animals, which means cutting off lots of trees. This leads to deforestation. But synthetic fibres are obtained by chemical processing of petrochemicals and hence help in conservation of forests.

Question 5:  What properties of plastics make them so useful?

Answer: Characteristic properties of plastics as follows

• Plastic is non-reactive
• Plastic is light, strong and durable
• Plastics are poor conductors

Question 6:  Why is a plastic bucket preferred over an iron bucket?

Answer: Plastic bucket preferred over an iron bucket because

Question 7:  What are some uses of nylon?

Answer: Uses of Nylon

• Nylon is used to make articles such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc.
• It is also used for making parachutes and ropes for rock climbing.

Question 8:  Why is acrylic fibre more popular than wool?

Answer: Acrylic fibre is more popular than wool because

• Clothes made from acrylic are relatively cheaper.
• They are available in a variety of colours.
• Synthetic fibres are more durable.

Question 9: Name two polyester fabrics and write their uses.

Answer:   Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn.

PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Question 10: Why should we not wear synthetic clothes while working in in the kitchen or in a laboratory?

Answer: Synthetic fibres melt on heating. If the clothes catch fire, it can be disastrous. The fabric melts and sticks to the body of the person wearing it. We should, therefore, not wear synthetic clothes while working in in the kitchen or in a laboratory.

Question 11: Differentiate between natural and synthetic fibres.

Answer: Difference between natural and synthetic fibres

Question 12: “Even though plastics are very useful, they are not environment friendly.” Justify the statement.

Answer: Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.

Question 13: ‘Avoid plastics as far as possible’. Comment on this advice.

Answer: Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution. Thus, we should avoid plastic as far as possible.

Question 14: Suggest some ways to solve plastic pollution. Or How can pollution due to plastics be solved?

Answer: Ways to solve plastic pollution

• The biodegradable and non-biodegradable wastes should be collected separately and disposed off separately.
• Recycle the plastic waste.

Question 15: Explain the difference between the thermoplastic and thermosetting plastics.

  Question 16: Why we should not throw polybags in the water bodies or on the road?

Answer: We should not throw polybags in the water bodies or on the road because:

• Cow while eating garbage waste food items swallow the polythene bags and wrappers of food. The plastic material chokes the respiratory system of these animals, or forms a lining in their stomachs and can be the cause of their death.
• The polybags carelessly thrown here and there are responsible for clogging the drains, too.

Question 17: Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’: Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Question 18: Describe an activity to show that thermoplastic is a poor conductor of electricity.

Answer: In order to show that thermoplastic is a poor conductor of electricity, we will design a circuit. For that, we need a bulb, some wires, a battery, a piece of metal and a plastic pipe. After switching on the current, the bulb glows in the former case. In the latter case, the bulb does not glow. Hence a plastic pipe (which is a thermoplastic) is shown to be a poor conductor of electricity.

Question 19: Differentiate between biodegradable and non-biodegradable materials.

Answer: Difference between biodegradable and non-biodegradable materials

At Study Path, you can also learn more about Class 8 Science Chapter 3 Synthetic Fibres and Plastics by accessing the free exhaustive list of study materials and resources related to the chapter such as NCERT Solutions, Notes, Important Questions, and MCQ.

Case Study Based Questions: Some Natural Phenomena | Science Class 8 PDF Download

Case study 1.

Roy and his friends were swimming in a pool. Suddenly he saw a huge flash of light in the sky and heard a loud sound of thunder. His friends continued swimming but Roy asked everyone to stop swimming and be safe. Few of his friends immediately got into the car. Roy and a few of them went inside the nearby building.

Q1: What should Roy and his friends do to save themselves from a thunderstorm? (a) They should stop swimming and stand in the pool. (b) They should stop swimming and go inside a building. (c) They should continue swimming. (d) They should run immediately and take shelter under a tall tree. Ans: (b) Sol: During a thunderstorm, it is safest to get out of the water and seek shelter inside a building to avoid lightning strikes and electrical hazards.

Q2: What should be done by Roy’s friends who got into the car? (a) They should stay inside the car with doors and windows closed. (b) They should stay inside the car with doors and windows open. (c) They should stay inside the car with doors closed but windows opened. (d) They should stay inside the car with doors opened but windows closed. Ans: (a) Sol: Staying inside a car with doors and windows closed provides a safe environment during a thunderstorm because the car’s metal body acts as a Faraday cage, protecting occupants from lightning.

Q3: Identify the correct statement/statements related to lightning and thunderstorm. i. Lightning is an electric discharge that occurs in nature on a large scale. ii. Lightning Conductor is a device used to protect buildings from the effect of lightning. iii. It is safe to travel on a motorbike during a thunderstorm. (a) Both i and ii (b) Both ii and iii (c) Only i (d) Only iii Ans: (a) Sol: Lightning is indeed an electric discharge and a lightning conductor is used to protect buildings. However, it is not safe to travel on a motorbike during a thunderstorm due to the risk of being struck by lightning.

Case Study 2

Seetha prepared an electroscope as shown in the figure. She has replaced the copper wire with ebonite rod. When charged body was bought in contact with the ebonite rod, she observed that the aluminium strips did not diverge. Q: What is the reason behind it?

Ans:  The aluminium strips did not diverge because the ebonite rod is an insulator and does not conduct electricity. In an electroscope, the metal wire or rod (usually made of a conductor like copper) is essential for conducting the charge from the charged body to the aluminium strips. Since the ebonite rod is a non-conductor, it prevents the flow of charge to the aluminium strips, which is why they did not diverge. For the electroscope to function properly and show divergence of the strips, a conductive material must be used to transfer the charge.    

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• Reproduction in Plants Class 7 Case Study Questions Science Chapter 8

Last Updated on October 22, 2024 by XAM CONTENT

Hello students, we are providing case study questions for class 7 science. Case study questions are the new question format that is introduced in CBSE board. The resources for case study questions are very less. So, to help students we have created chapterwise case study questions for class 7 science. In this article, you will find case study questions for cbse class 7 science chapter 8 Reproduction in Plants.

Table of Contents

Case Study Questions on Reproduction in Plants

Question 1:

Read the given passage below and answer the question:

Reproduction is necessary for all living organisms. It is an ability to reproduce is a common characteristic of all living organisms. The parts of a plant are grouped into vegetative parts and reproductive parts. There are several ways by which plants produce their offspring, it is generally groups into two types: asexual and sexual reproduction. Asexual reproduction is not only found in plants but it is also the primary form of reproduction for single-celled organisms.

Q.1. Which parts of a plant is involved in the sexual reproduction? (Easy) (a) Flower (b) Fruit (c) Seed (d) All of these

Difficulty Level: Easy

Ans. Option (a) is correct Explanation: Flowers are the reproductive parts of a plant.

Q.2. Which of the following statement is true about asexual reproduction: (Medium) (a) plants can give rise to new plants without seeds. (b) plants can reproduce on its own without the involvement of another individual. (c) vegetative reproduction is a type of asexual reproduction. (d) All of the above.

Difficulty Level: Medium

Ans. Option (d) is correct. Explanation: In asexual reproduction, plants can give rise to new plants without seeds. In asexual reproduction an individual can reproduce on its own without the involvement of another individual of the same species. The type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds is called vegetative propagation.

Q.3. Asexual reproduction in plants occurs through: (a) budding, fragmentation, fertilisation and spore formation (b) fragmentation, vegetative propagation, budding and spore formation (c) vegetative propagation, spore formation, pollination and budding (d) fragmentation, fertilisation, vegetative propagation, and spore formation

Ans. Option (b) is correct. Explanation: Asexual reproduction in plants occurs through budding, fragmentation, vegetative propagation and spore formation. Pollination and fertilisation are involved in sexual reproduction in plants.

Q.4. Name and define the type of reproduction which occurs using vegetative parts? Name the vegetative parts of plants.

Ans. The reproduction using vegetative parts is called vegetative propagation. Vegetative propagation is a type of asexual reproduction in which new plants are produced from vegetative parts of the plant like roots, stems, leaves and buds.

Q.5. Why is reproduction necessary? What will happen if there is no reproduction?

Difficulty Level: Hard

Ans. Reproduction is essential for the continuation of a species. It is a biological process through which living organisms produce offspring’s similar to them. In the absence of reproduction, the species will not be able to exist for a long time and may soon get extinct.

• Electric Currents and Its Effects Class 7 Case Study Questions Science Chapter 10
• Motion and Time Class 7 Case Study Questions Science Chapter 9
• Transpirations in Animals and Plants Class 7 Case Study Questions Science Chapter 7
• Respiration in Organisms Class 7 Case Study Questions Science Chapter 6
• Physical and Chemical Changes Class 7 Case Study Questions Science Chapter 5
• Acids Bases and Salts Class 7 Case Study Questions Science Chapter 4
• Heat Class 7 Case Study Questions Science Chapter 3

Nutrition in Animals Class 7 Case Study Questions Science Chapter 2

Nutrition in plants class 7 case study questions science chapter 1, topics from which case study questions may be asked.

• You will understand about different modes of reproduction in plants.
• You will learn about vegetative reproduction and its types.
• You will understand the formation of seeds and fruit.
• You will understand the process of seed dispersal.

All living things eat, drink, grow and reproduce. Animals and human beings produce offspring of same as of them. Plants also produce same kind of plants by the process of reproduction.

Reproduction is the process of producing offsprings. In plants reproduction is categorised into two types: (i) asexual, and (ii) sexual reproduction

For further practice on case study questions related to Class 7 Science Chapter 7 Reproduction in Plants, we recommend exploring the link given below.

Frequently Asked Questions (FAQs) on Reproduction in Plants Case Study Questions

Q1: what are case study questions for cbse examinations.

A1: Case study questions in CBSE examinations typically involve scenarios or real-life examples, requiring students to apply their understanding of concepts to solve problems or analyze situations.

Q2: Why are case study questions important for understanding class 7 science chapters?

A2: Case study questions provide a practical context for students to apply theoretical knowledge to real-world situations, fostering deeper understanding and critical thinking skills.

Q3: How do case study questions differ from other question types?

A3: Unlike direct questions that test specific knowledge, case study questions involve analyzing a scenario, understanding the context, and applying various scientific concepts to answer the questions. They test higher-order thinking skills such as analysis, synthesis, and evaluation.

Q4: Are there any resources available online for students to practice case study questions on class 7 science chapters for CBSE exams?

A4: Yes, several educational websites offer case study questions for CBSE students preparing for science examinations. We also offer a collection of case study questions for all classes and subject on our website. Visit our  website  to access these questions and enhance your learning experience. There is another website Physics Gurukul that offers a large collection of case study questions.

Q5: How can students effectively prepare for case study questions on Reproduction in Plants for CBSE exams?

A5: Effective preparation strategies include regular revision of concepts, solving practice questions, analyzing case studies from previous exams, seeking clarification on doubts, and consulting with teachers or peers for guidance and support.

Q6: How can teachers incorporate case study questions on Reproduction in Plants class 7 science into classroom teaching?

A6: Teachers can integrate case studies into lesson plans, group discussions, or interactive activities to engage students in active learning, promote problem-solving skills, and facilitate a deeper understanding of Reproduction in Plants.

Q7: What steps should I follow to correctly answer case study questions?

A7: Follow these steps: Read the case study carefully. Understand the scenario and the information provided. Identify the key concepts. Determine which scientific principles or concepts are relevant to the case study. Analyze the information. Break down the information, identify relationships, and note any data or facts given. Answer the questions. Apply your knowledge to answer the questions, ensuring that your responses are based on the case study and the relevant scientific concepts.

Q8: What should I check when reading a case study?

A8: Check the following: Context and background: Understand the setting and context of the case study. Key facts and data: Identify important details, data points, and observations mentioned. Relevant concepts: Recognize which scientific concepts and principles are applicable. Questions asked: Carefully read each question to understand what is being asked and how it relates to the case study.

Q9: What are common mistakes to avoid when answering case study questions?

A9: Common mistakes include: Not reading the case study carefully: Missing important details and context. Ignoring key concepts: Failing to identify and apply relevant scientific principles. Superficial analysis: Providing answers that lack depth and do not fully address the questions. Making assumptions: Adding information not provided in the case study or making unsupported assumptions.

Q10: How can I ensure my answers are thorough and well-structured?

A10: Ensure your answers are thorough and well-structured by: Organizing your thoughts: Structure your answer logically with a clear introduction, body, and conclusion. Using evidence: Support your answers with specific information from the case study. Applying relevant concepts: Clearly explain how scientific principles relate to the case study. Reviewing your answers: Check for completeness and accuracy, ensuring all parts of the question are addressed.

Q11: What are the important keywords from the chapter “Reproduction in Plants”?

A11: Important keywords from the chapter “Reproduction in Plants” are given below: Gametes: The reproductive cells of an organism. Zygote: A cell formed as a result of fusion of male and female gametes. Pollen grains: Microscopic spores found in anther. Dispersal: The process of spreading things. Vegetative: Relating to reproduction in plants achieved through asexual mode. Budding: Having or developing buds in a plant. Fragmentation: A type of vegetative reproduction in plants. Spore: Cells produced by fungi, ferns and bacteria.

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