Important Questions for CBSE Class 8 Science Chapter 3 - Synthetic Fibres and Plastics

Very Short Answers Questions                                                                         1 Mark

1. Why plastic is used in aircraft and spaceships.

1. Plastics are lighter compared to metals.

2. Plastics are cheaper.

3. Plastics are easy to handle.

4. Plastic can be recycled.

Ans: A. Plastics are lighter compared to metals.

2. Which one of the following is non-biodegradable material?

1. Paper

2. Metal cans

3. Cotton cloth

4. Wood 

Ans: B. Metal cans

3. Plastics are poor conductor of ________

1. Air  

2. Water 

3. Heat and electricity

4. None of these

Ans: C. Heat and electricity

4. What is PET?

1. Polyester

2. Polyester and Terylene

3. Poly Ethene Terephthalate

4. Poly Ethene Terylene

Ans: C. Poly Ethene terephthalate

5. Rajesh found that woolen blankets were expensive as it was made from natural fibre. He wanted a blanket that was similar to woolen blanket, but cheaper. He can buy a blanket made of ________ fibre.

1. Silk 

2. Nylon 

3. Acrylic 

4. Cotton 

Ans: C. Acrylic

6. Terylene is a popular form of _________.

1. Nylon 

2. Plastic 

3. Rayon  

4. Polyester 

Ans: D. polyester

Short Answers Questions                                                                                2 Marks

1. Write any two examples of polyester fabric.

Ans: A polyester is a type of fabric and its two examples are terylene and PET.

2. Write any one use of Bakelite.

Ans: Electrical switches are made using Bakelite.

3. Polycot is a mixture of _______ and _______ .

Ans: Polycot is a mixture of polyester and cotton.

4. Synthetic fibres are obtained by chemical processing of _________.

Ans: Synthetic fibres are obtained by chemical processing of petrochemicals.

5. Choose the odd one out – nylon, rayon, silk, acrylic.

Ans: Silk (nylon, rayon, and acrylic are synthetic fibres whereas silk is natural).

6. Give two examples of thermosetting plastics.

Ans: Two examples of thermosetting plastics are bakelite and melamine.

7. _______ is a large single unit made up of many repeated small units.

Ans: Polymer is a large single unit made up of many repeated small units.

8. What is the $\text{5R}$ principle?

Ans: $ \text{5R} $ principle works on the following rules:

• Reduce

• Reuse

• Recycle

• Recover 

• Refuse

9. __________ is made up of a large number of glucose units.

Ans: Cellulose is made up of a large number of glucose units.

Short Answer Questions                                                                                  3 Marks

1. Draw a simple diagram of the linear and cross-linked arrangement of units in plastic.

Ans: Diagrams of linear and cross-linked arrangement of units in plastic are given below:

2. List any three characteristic properties of plastic.

Ans: The three characteristic properties of plastic are:

1. Non-reactive in nature.

2. They are light in weight but are strong and durable.

3. Poor conductor of heat and electricity.

3. What do you mean by biodegradable?

Ans: As the name suggests, biodegradable means naturally degradable i.e., the products that are environmentally friendly and are capable of decomposing by natural processes such as the action of bacteria. For example – paper, cotton cloth, wood, etc.

4. Why is nylon suitable for making clothes?

Ans: Nylon is suitable for making clothes because it is strong, elastic, light, lustrous, and easy to wash. 

5. ‘Plastic is a poor conductor of heat and electricity. With an example to justify the statement.

Ans: Plastic is a poor conductor of heat and electricity. This statement can be justified because the electric wire has a plastic covering. Also, the handles of screwdrivers and testers are made of plastic. The plastic covering is used because it prevents the chances of electric shock. 

6. Sort the following materials into - biodegradable and non-biodegradable plastic bottle, flower, wooden bowl, banana peel, cotton cloth, soda can

Ans: Biodegradable products are flowers, wooden bowls, banana peels, and cotton cloth. Non-biodegradable products are plastic bottles and soda cans.

7. Write two differences between natural and synthetic fibre.

Ans: The differences between natural and synthetic fibre are:

8. Answer the following:

1. Which is the fibre obtained from the natural source?

Ans: The fibre that is obtained from the natural source is cotton.

2. Write a short note on this fibre.

Ans: Rayon is obtained from a natural source; it grows in a protective case around the seeds of the cotton plants. It is cheaper than silk. It is spun into yarn or thread and is used to make a soft, breathable fabric. The fabrics made of cotton are used in clothing, furnishing, and industrial areas. Cotton is mixed with rayon to make bed sheets.

9. What is the disadvantage of synthetic fibre?

Ans: The main disadvantage of synthetic fibres is that they are inflammable i.e., they melt on heating and if clothes catch fire, the fabric melts and sticks to the body of the person wearing it. 

10. Being responsible citizens, how can we avoid plastics?

Ans: Being a responsible citizens, we can avoid plastics by the following practices:

1. Using steel or copper water bottles instead of plastic.

2. Using cotton or jute carry bags instead of plastic.

3. Using a steel lunch box instead of a plastic one.

11. Identify and correct the errors in the following statements.

1. Polyester is a strong fibre that is used for making parachutes and ropes for rock climbing.

Ans: Instead of polyester, nylon should be there as all the characteristics given in the statement are of nylon. Nylon is a strong fibre that is used for making parachutes and ropes for rock climbing.

2. Natural fibres are more durable and affordable which makes them more popular than synthetic fibres.

Ans: The use of synthetic and natural are interchanged. Synthetic fibres are more durable and affordable which makes them more popular than natural fibres.

Long Answer Question                                                                                   5 Marks

1. Describe the following with examples:

1. Thermoplastic

Ans: Thermoplastics are materials that get deformed easily on heating. They are malleable and can be easily bent. Some examples of thermoplastics are polythene and PVC. Thermoplastics are mainly used in the manufacturing and production of toys and combs.

2. Thermosetting plastics.

Ans: Thermosetting plastics are materials that can be moulded only once and cannot be softened by heating. Some examples of thermosetting plastics are bakelite and melamine. Melamine resists fire and can tolerate heat, it is used for making floor tiles, kitchenware, and fabrics. Bakelite is a poor conductor of heat and electricity and is used for making electrical switches, handles of various utensils, etc. 

2. Write the applications of plastics in different industries.

Ans: Some applications of plastics in different industries are:

1. Healthcare industry – packaging of tablets, threads used for stitching wounds, syringes, and doctors’ gloves.

2. Cooking – some microwave plastic cookware.

3. Cooking – Teflon coating is used for non-stick coating on cookware.

4. Uniforms of firemen – they have a coating of melamine plastic. 

3. Complete the following crossword using the clues given below.

Across

3. Fabrics do not wrinkle easily

4. Used for making parachutes and stockings

Down

1. Prepared by using wood pulp

2. Used to make non-stick cookware

Ans: The solved cross-word is given below:

4. The government of India has declared many areas as “Plastic Free Zone” and has banned the use of plastic and polythene bags. Why do you think the government has taken this decision? What are the possible hazards of plastics?

Ans: Plastic takes a long time to degrade and is harmful to the environment. It has a negative impact on the environment. Furthermore, the synthetic materials’ burning process is slow, and it does not simply burn fully. It pollutes the air by releasing a large number of harmful gases into the atmosphere. Not only that, but it has a variety of effects on animals. They consume items such as polythene bags and food wrappers when consuming food trash in the rubbish. The plastic material suffocates these animals; respiratory systems or creates a lining in their stomachs, perhaps leading to death. Polybags tossed improperly are also responsible for obstructing drains. The government has outlawed plastic in specific locations as a result of the aforementioned activities.

5. With the help of activity show that synthetic fibre dries up faster than natural fibres.

Ans: Let’s take two identical cloth pieces, each about half a metre square. At least one of these should be made of natural fibre. The alternative option is to use synthetic fibre. You can enlist your parents; assistance in choosing these items. Soak the pieces in separate mugs with the same quantity of water in each. After five minutes, remove the pieces from the containers and place them in the sun for a few minutes. Compare the amount of water that is left in each container. 

Conclusion: Synthetic fibres take less time to dry than natural fibres because they absorb less water. 

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

Chapter 3 of Class 8 is referred to as “Synthetic fibers and Plastics”. The chapter deals with the introduction of Synthetic fibers and plastics, their classification, properties, and their advantages as well. 

Synthetic Fiber: 

Synthetic fiber is typically a chain of small units that are connected; a chemical product is a small unit. Human beings make synthetic fibers, so they are called synthetic or man-made fibers. Cotton, wool, silk, etc. that are obtained from plants or animals are the natural source of fibers. In today's era of modernization, synthetic fibers are omnipresent. They are around us everywhere, in garments, furnishings, home appliances, etc. Fiber is considered a thin thread of an artificial or natural material. Synthetic fibers are man-made fibers. It is a chain of units that are assembled to form a polymer. These tiny units, placed together to form a larger structure, contain a polymer. Some polymers exist freely in nature, however. For example, cotton consists of a polymer called cellulose, which consists of a group of glucose units in turn. During the extrusion phase of fiber, these fibers are formed either by one of these spinning processes, melt, wet or dry, at the manufacturing point. After undergoing various refining processes, synthetic fibers are prepared using raw materials such as petroleum. The synthetic fibers have plenty of important questions that deals with day to day life and are easily available. While preparing the chapter, one must go through the questions and can score well.

However, one of the drawbacks of using this fiber is that these fibers appear to melt when heated. Some synthetic fibers are high in strength and not easily spread, such as polyesters and polyamides, so they are used in textiles.

There are different types of synthetic fibers:

Rayon:

•  Artificial Silk 

• Rayon fiber is obtained from the chemical treatment of wood pulp.

• Rayon is a soft, absorbent, and comfortable fabric.

• Dyeing in a wide range of colours is simple.

• To make bedsheets, rayon is mixed with cotton.

• For making carpets, Rayon is mixed with wool.

Nylon:

• first synthetic fiber 

• Fiber prepared from coal and water.

• Nylon is very shiny, simple, and elastic to wash.

• It dries rapidly and retains its form.

• Nylon is used for car seat belts, sleeping bags, socks, ropes, etc.

• For rock climbing, making parachutes, and fishing nets, nylon is also used in ropes.

Polyester: 

• It is wrinkle-free fiber 

• From coal, water, air, and petroleum, this form of synthetic fiber is obtained.

• Repeating units of a compound known as esters are made of polyester.

• Polyester is easy to wash and stays wrinkle-free, making dress material very fitting.

• Polyester retains and stays crisp in its form.

• In making ropes, nets, raincoats, jackets, etc, polyester is used.

Properties of Synthetic Fiber:

• These fibers are naturally crystalline filaments that are High elastic and sturdy.

• Far cheaper than natural fiber 

• Stronger than a natural fiber,

• Quite durable, very durable,

• Dry up easily, therefore, used in the manufacture of dress materials

• Compared to natural fibers, readily available

• Can easily be managed

• Simple to clean

• Chemically resistant fibers

• Such fibers do not shrink.

• It is consumer-friendly because it has the following characteristics: waterproof, stain-resistant, stretchable material.

• There is little or no dirt or impurity,

• Highly easy to use

• As seen in natural fiber, the fabric is not susceptible to any insect damage due to its man-made nature.

Benefits of Synthetic Fibres:

• Synthetic fibers are very durable and don't easily wrinkle.

• They are elastic and can be stretched quickly.

• They are powerful and can sustain heavy loads.

• They are soft and are also used in clothing supplies.

• They are cheaper than natural fibers in comparison.

• The drawbacks of synthetic fibers

• There is no absorption of moisture by most synthetic fibers.

• If washed using hot water, synthetic fiber may be affected.

• Compared to natural fibers, they catch fire easily.

Synthetic Fibers and Plastics Class 8 Important Questions

Plastic, like synthetic fibers, is also a kind of polymer. A common example of plastic is polythene (Poly + ethene). The word widely used to describe a wide variety of synthetic or semi-synthetic materials used in a large and growing range of applications is plastics. You'll find plastic everywhere you look. To help make our lives cleaner, smoother, safer, and more enjoyable, we use plastic items. In the clothing we wear, the houses in which we live, and the vehicles in which we drive, we find plastic. The toys we play with, the screens we watch, the IT instruments we use, and plastics are all included in the medical devices we profit from.

Just like wood, paper, or wool, plastics are organic materials. Natural products such as cellulose, coal, natural gas, salt, and, of course, the raw materials used to manufacture plastics. The word " plastic " is derived from the word " plastikos " in Greek, which means fit for molding. This refers to the malleability or plasticity of the material during production, which enables it to be cast, pressed, or extruded into a variety of forms, such as films, fibers, plates, tubes, bottles, boxes, and much more.

Plastic stays around for ages in the environment, threatening wildlife and spreading toxins. Plastic leads to global warming as well. Almost all plastics are produced from chemicals that come from planet-warming fuel processing (gas, oil, and even coal).

Plastic is the common material that is used by an individual in daily usage. This is one of the important topics which is asked in the examination. So the students must undergo all the important questions of the chapter synthetic fibers and plastics to score well in the examinations.

Melamine is fire resistant and can better tolerate heat than other plastics; it is therefore used to make floor tiles, kitchenware, and fabrics. A material that is decomposed by natural processes, e.g. by bacterial action, is known as biodegradable. A material is known as non-biodegradable, which can not be easily decomposed by natural processes. Plastic is not generous to the climate.

Different Types of Plastics:

Forms of Plastic Materials 

1. Thermoplastic: Thermoplastic is known as thermoplastic for plastics that can be quickly bent or deformed when heated. Examples of thermoplastics are PVC and polythene.

2. Thermosetting Plastic: Thermosetting plastics are referred to as plastics that are not deformed or softened on heating when once molded. E.g. Melamine and Bakelite. Bakelite is a poor heat and electricity conductor; it is therefore used in the manufacture of electric switches, handles of different utensils, etc.

Characteristics of Plastics

A weak conductor of heat and electricity is plastic. Plastic and several chemicals do not react with air and water. Lightweight, sturdy, inexpensive, and very strong are plastics. Non-biodegradable substances are plastics. It takes several years to decompose and often it does not decompose at all. Plastic is also not eco-friendly. Not rusting plastic.

Uses of Plastics:

Plastics are highly flexible materials and are suitable for a wide variety of applications for consumer and industrial use. The relatively low density of most plastics brings the benefits of lightweight to plastic products. And, although most have outstanding thermal and electrical insulation properties, certain plastics can, if necessary, be made to conduct electricity. They are resistant to the corrosion of many substances that attack other materials, making them durable and acceptable for use in harsh environments. Some are translucent, making it possible for optical devices. They can be easily molded into complex forms, facilitating the incorporation of other materials into plastic goods and making them suitable for a wide range of functions. Also, if the physical properties of a given plastic do not fully comply with the stated specifications, the balance of properties may be changed to satisfy the requirements of the particular application by incorporating reinforcing fillers, colours, foaming agents, flame retardants, plasticizers, etc.

Effect of Plastic on the Environment:

Plastic remains around for years in the climate, damaging biodiversity and transmitting contaminants. Plastic leads to global warming as well. Almost all plastics are produced from chemicals that come from planet-warming fuel processing (gas, oil, and even coal). Toxic emissions cause damage to humans, animals, and plants due to plastic contamination. Plastic will take hundreds or even thousands of years to break down, so the damage to the ecosystem is long-lasting. When plastic is consumed, toxins make their way up the food chain and can even be found in the fish people eat. Ingestion, suffocation, and entanglement of hundreds of aquatic organisms are the most noticeable and alarming impacts of marine plastics. When their stomachs are packed with plastic litter, marine wildlife such as seabirds, whales, fish, and turtles, mistake plastic waste for prey, and most die of starvation. Microplastics that reach the human body through direct exposure through ingestion or inhalation can lead to a variety of health effects, including inflammation, genotoxicity, oxidative stress, apoptosis, and necrosis, linked to a variety of negative health outcomes, including cancer, cardiovascular diseases.

Benefits of Referring to Important Questions of Chapter 3 - Synthetic Fibres and Plastics

Students will get many benefits while referring to the important questions of class 8 Chapter 3 - Synthetic Fibres and Plastics. Here is the list of benefits given below:

• Solutions are designed by experienced teachers and subject-matter experts.

•  Solutions are written in a comprehensive and easy-to-understand language. 

• Answers to each question are described in the attached PDF.

• Students can download the PDF and start studying anywhere and anytime.

So, my dear child, waiting for what? Start your preparation now, download the free PDF and score high in the exams.

Conclusion

Understanding important questions related to CBSE Class 8 Science Chapter 3 - Synthetic Fibres and Plastics is crucial for a comprehensive understanding of the topic. This chapter explores the world of synthetic fibers and plastics, their properties, uses, and environmental impact. By addressing key questions, students can enhance their knowledge and grasp concepts more effectively. Some important questions may revolve around the types of synthetic fibers and their advantages, the process of making plastics, their recycling methods, and the impact of plastics on the environment. By delving into these questions, students can develop a deeper understanding of synthetic fibers and plastics, enabling them to make informed choices and contribute to sustainable practices in the future.