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Q1. Bakelite is a typical _______ plastic.

Solution

Bakelite is a typical thermosetting plastic.

Q2. Heating a PET bottle will make it _______ and lose it's shape.

Solution

Heating a PET bottle will make it soft and lose it's shape.

Q3. Which of the following is not a property of plastics?

• 1) They are light.
• 2) They are water proof.
• 3) They are relatively cheap.
• 4) They are not durable.

Solution

Plastics are durable as they are strong and resistant to decay, rusting and chemical attack.

Q4. Which among the following is not a natural polymer?

• 1) Cotton
• 2) Nylon
• 3) Silk
• 4) Wool

Solution

Nylon is a synthetic (man-made) polymer.

Q5. The number of repeating units of monomers in polymers is

• 1) Very large
• 2) 5 to 10
• 3) 2 to 5
• 4) 10 to 20

Solution

Polymers are very large molecules formed by joining small units called monomers.

Q6. The waste created by plastics is environment friendly.

• 1) False
• 2) True

Solution

False. The waste created by plastics is hazardous to environment.

Q7. It is advised not to throw plastic in garbage dumping area as:

• 1) Plastics produce rotting smell.
• 2) They fly.
• 3) They are biodegradable.
• 4) It chokes respiratory system of animals.

Solution

The plastic material chokes the respiratory system of animals and can cause death.

Q8. Select the correct characteristic of thermosetting polymers.

• 1) Cross-linked chain polymers
• 2) Are soft
• 3) Can be reused
• 4) Good conductor of heat

Solution

Thermosetting plastics are heavily cross-linked and hence can't be remoulded after reheating.

Q9. All plastics are cross-linked polymers.

• 1) True
• 2) False

Solution

False. Some plastics are cross-linked polymers while some are linear polymers.

Q10. Rayon is chemically made by treatment of

• 1) Cellulose
• 2) Protein
• 3) Glucose
• 4) Amylase

Solution

Rayon is made from wood-pulp. The wood obtained from plants are made of cellulose.

Q11. All plastics are polymers and all polymers are plastics.

• 1) True
• 2) False

Solution

False. All plastics are polymers but all polymers are not plastics.

Q12. Plastics that can be heated and reshaped are 

• 1) All plastics
• 2) All polymers
• 3) Thermoplastics
• 4) Thermosetting plastics

Solution

Thermoplastic can be heated and reformed over and over again.

Q13. Bio-degradable substances are materials that:

• 1) Undergo natural decomposition by bacteria
• 2) Melt on heating
• 3) Can grow
• 4) Are used as food for animals

Solution

Bio-degradable substances are materials that get decomposed by microbial action.

Q14. Rayon cannot be dyed in different colours.

• 1) True
• 2) False

Solution

False. Rayon can be dyed in different colours.

Q15. Synthetic fibres ________ on burning.

Solution

Synthetic fibres melt on burning.

Q16. Select the type of plastic that can be recycled.

• 1) None
• 2) Both
• 3) Thermoplastic
• 4) Thermosetting

Solution

Thermoplastics can be heated and reformed over and over again. This property helps in recycling.

Q17. Rayon is first fully man-made fibre.

• 1) True
• 2) False

Solution

False. Nylon is first fully man-made fibre.

Q18. Since plastics take several years to degrade, it is classified as ________.

Solution

Since plastics take several years to degrade, it is classified as non-biodegradable.

Q19. Clothes made of ________ should be worn in kitchen.

Solution

Clothes made of natural fibres should be worn in kitchen.

Q20. Polythene is prepared from which monomer?

• 1) Ethene
• 2) Ethane
• 3) Methane
• 4) Acetylene

Solution

Ethene molecules join to form polythene.

Q21. Which of the following is a property of plastics?

• 1) All of the above
• 2) Wrinkle free
• 3) Insoluble in water
• 4) Mouldable

Solution

Plastics are mouldable, wrinkle free and insoluble in water and hence have a number of applications and uses.

Q22. You must have seen PET jars and bottles used by your mother in kitchen for storing rice, sugar etc. What are these PET jars and bottles made of?

Solution

PET jars and bottles used in kitchen are made of polyester.

Q23. Polyester shirts are easy to maintain.

• 1) False
• 2) True

Solution

True

Q24. Which synthetic fibre was first discovered?

• 1) Nylon
• 2) Polyester
• 3) Rayon
• 4) Polycot

Solution

Nylon was the first fully synthetic fibre.

Q25. Which synthetic fibre is known as artificial silk?

• 1) Nylon
• 2) Polyester
• 3) Terylene
• 4) Rayon

Solution

Rayon has properties similar to silk, but is man-made fibre obtained by chemically treating wood-pulp.

Q26. Nylon is made from

• 1) Animals
• 2) Both plants and animals
• 3) Coal, water, air
• 4) Plants

Solution

Nylon is first fully synthetic fibre prepared from coal, water and air.

Q27. Synthetic polymers cause environmental pollution as they are ________.

Solution

Synthetic polymers cause environmental pollution as they are non-biodegradable.

Q28. Which of the following is not a synthetic fibre?

• 1) Coir
• 2) Rayon
• 3) Acrylic
• 4) Nylon

Solution

Coir is a natural fibre obtained from plants.

Q29. Which of the following is the most commonly used polyester?

• 1) Rayon
• 2) Terylene
• 3) Cotton
• 4) Nylon

Solution

Terylene is the most commonly used polyester. It is blended with natural fibres to improve its properties.

Q30. Rayon was originally called _______.

Solution

Rayon was originally called artificial silk.

Q31. Plastics cause environmental pollution as it releases greenhouse gases on burning.

• 1) True
• 2) False

Solution

True

Q32. What type of resources are thermoplastics?

• 1) Non-renewable
• 2) Renewable
• 3) Natural
• 4) Can be made easily

Solution

Thermoplastics are a renewable resource as it can be recycled and reused.

Q33. Name the following: A. Polyester mixed with cotton B. Polyester mixed with wool

Solution

(A) When polyester is mixed with cotton, it is called Polycot.(B) When polyester is mixed with wool, it is called Polywool.

Q34. ________ is used in making parachutes.

Solution

Nylon is used in making parachutes.

Q35. PET is a very familiar form of polyester.

• 1) True
• 2) False

Solution

True

Q36. Thermoplastics become soft on heating and can bend easily.

• 1) True
• 2) False

Solution

True

Q37. The _______ type of plastic does not go back into its original form when heated.

Solution

The thermosetting type of plastic does not go back into its original form when heated.

Q38. Plastic materials are _______.

Solution

Plastic materials are water proof.

Q39. Synthetic polymers cause environmental pollution.

• 1) False
• 2) True

Solution

True

Q40. Most of the fabrics made from synthetic fibres should be ironed very carefully. Why?

Solution

The fabrics made from synthetic fibres should be ironed very carefully because they melt very easily on heating.

Q41. (a) Explain the difference between thermoplastics and thermosetting plastics (two differences each). (b) Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride (PVC) (c) Explain why, plastic containers are preferred for storing food.

Solution

(a) Thermoplastics Thermosetting plastics 1. It can be softened repeatedly by heating and can be moulded into different shapes again and again. 1. Once set, it does not become soft on heating and cannot be moulded a second time. 2. These can be used for making those articles which do not get too hot and are flexible. 2. These are used for making those articles which may get too hot during use and are hard and rigid.   (b) Thermoplastics: Polythene and Polyvinyl chloride (PVC).       Thermosetting plastics: Melamine and Bakelite. (c) It is because of the lower price, easy availability, lightweight, durability and corrosion resistance of plastic that the plastic containers are preferred for storing food.

Q42. Why is it advised not to wear fabrics made of synthetic fibres while working in kitchen or near any other source of fire?

Solution

We should not wear fabrics made of synthetic fibres while working in kitchen or near any other source of fire because they catch fire easily.

Q43. The small repeating unit of polymer is known as

• 1) Co-polymer
• 2) Monomer
• 3) Dimer
• 4) Homomer

Solution

Polymer is a large molecule made up of many smaller and identical repeating units called monomers.

Q44. Terylene is a typical ________ polymer.

Solution

Terylene is a typical polyester polymer.

Q45. Place a plastic spoon and a metal spoon in a jug of hot water. Which one can you hold directly? Why?

Solution

We can hold the plastic spoon directly in a jug of hot water. This is because plastics are poor conductor of heat.

Q46. Both nylon and rayon are man-made fibres. Is there any difference between the two? Explain.

Solution

Yes, nylon and rayon differ in the source from which they are obtained. Rayon is obtained by the chemical treatment of wood pulp which is a natural source while nylon is made without using any natural raw material. It is obtained from coal, water and air.

Q47. What is meant by biodegradable and non-biodegradable materials? Give examples of two biodegradable and two non-biodegradable materials.

Solution

A material which gets decomposed through natural processes such as the action of bacteria is called biodegradable material. Examples: Peels of vegetables and fruits, wood.  A material which is not easily decomposed by natural processes such as action of bacteria is called non-biodegradable material. Examples: Plastics, glass.  

Q48. Plastic pot and pan handles in kitchen utensils suggest that plastic is thermal ________.

Solution

Plastic pot and pan handles in kitchen utensils suggest that plastic is thermal insulator.

Q49. Give reason. Thermoplastics can be recycled.

Solution

Thermoplastics are made up of linear chains of molecules with a few cross linkages. This allows them to soften when heated and to be bent into a variety of shapes and forms.

Q50. We should not wear fabrics made from synthetic fibres in hot summer weather. Why?

Solution

We should not wear fabrics made from synthetic fibres in hot summer weather because most of the synthetic fibres absorb very little moisture. Thus, they become sticky when body sweats which makes them uncomfortable to wear in hot weather.

Q51. Why are plastics not suitable for building large and heavy structures?

Solution

Plastics are flexible and are non-rigid. Hence, they are not suitable for building large and heavy structures.

Q52. Give four common uses of nylon fibres.

Solution

Nylon fibres are most often used for making stockings, tooth brushes, ropes and parachutes.

Q53. Burning of plastics is not advisable. Give one reason to support this statement.

Solution

Burning of plastics is not advisable as it releases poisonous gases into the atmosphere.

Q54. Polymers can be both thermal and electrical _________.

Solution

Polymers can be both thermal and electrical insulators.

Q55. What is the need for recycling plastic bottles? Is it advisable to dispose off the plastic wastes by burning? Give reasons.

Solution

Plastic bottles should be recycled as they are non-biodegradable and do not decompose easily. No, plastic wastes should not be burned for disposing them off because burning of plastic wastes gives out harmful gases which pollute the air.