Q1. Which of the following is not a synthetic fibre?
- 1) Coir
- 2) Acrylic
- 3) Nylon
- 4) Rayon
Solution
Coir is a natural fibre obtained from plants.
Q2. Select the type of plastic that can be recycled.
- 1) Both
- 2) Thermoplastic
- 3) None
- 4) Thermosetting
Solution
Thermoplastics can be heated and reformed over and over again. This property helps in recycling.
Q3. 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.
Q4. Which of the following is a property of plastics?
- 1) All of the above
- 2) Wrinkle free
- 3) Mouldable
- 4) Insoluble in water
Solution
Plastics are mouldable, wrinkle free and insoluble in water and hence have a number of applications and uses.
Q5. Which synthetic fibre is known as artificial silk?
- 1) Terylene
- 2) Rayon
- 3) Nylon
- 4) Polyester
Solution
Rayon has properties similar to silk, but is man-made fibre obtained by chemically treating wood-pulp.
Q6. What type of resources are thermoplastics?
- 1) Natural
- 2) Renewable
- 3) Can be made easily
- 4) Non-renewable
Solution
Thermoplastics are a renewable resource as it can be recycled and reused.
Q7. Polyester shirts are easy to maintain.
- 1) False
- 2) True
Solution
True
Q8. 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.
Q9. Which synthetic fibre was first discovered?
- 1) Nylon
- 2) Polyester
- 3) Rayon
- 4) Polycot
Solution
Nylon was the first fully synthetic fibre.
Q10. Polythene is prepared from which monomer?
- 1) Ethene
- 2) Methane
- 3) Ethane
- 4) Acetylene
Solution
Ethene molecules join to form polythene.
Q11. Bakelite is a typical _______ plastic.
Solution
Bakelite is a typical thermosetting plastic.
Q12. Select the correct characteristic of thermosetting polymers.
- 1) Cross-linked chain polymers
- 2) Can be reused
- 3) Good conductor of heat
- 4) Are soft
Solution
Thermosetting plastics are heavily cross-linked and hence can’t be remoulded after reheating.
Q13. Which of the following is the most commonly used polyester?
- 1) Terylene
- 2) Nylon
- 3) Cotton
- 4) Rayon
Solution
Terylene is the most commonly used polyester. It is blended with natural fibres to improve its properties.
Q14. All plastics are cross-linked polymers.
- 1) True
- 2) False
Solution
False. Some plastics are cross-linked polymers while some are linear polymers.
Q15. 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.
Q16. The number of repeating units of monomers in polymers is
- 1) 5 to 10
- 2) Very large
- 3) 10 to 20
- 4) 2 to 5
Solution
Polymers are very large molecules formed by joining small units called monomers.
Q17. Nylon is made from
- 1) Coal, water, air
- 2) Animals
- 3) Plants
- 4) Both plants and animals
Solution
Nylon is first fully synthetic fibre prepared from coal, water and air.
Q18. The small repeating unit of polymer is known as
- 1) Monomer
- 2) Homomer
- 3) Co-polymer
- 4) Dimer
Solution
Polymer is a large molecule made up of many smaller and identical repeating units called monomers.
Q19. Synthetic polymers cause environmental pollution as they are ________.
Solution
Synthetic polymers cause environmental pollution as they are non-biodegradable.
Q20. 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.
Q21. Plastics that can be heated and reshaped are
- 1) Thermoplastics
- 2) Thermosetting plastics
- 3) All plastics
- 4) All polymers
Solution
Thermoplastic can be heated and reformed over and over again.
Q22. It is advised not to throw plastic in garbage dumping area as:
- 1) They fly.
- 2) They are biodegradable.
- 3) Plastics produce rotting smell.
- 4) It chokes respiratory system of animals.
Solution
The plastic material chokes the respiratory system of animals and can cause death.
Q23. 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.
Q24. Rayon is chemically made by treatment of
- 1) Amylase
- 2) Protein
- 3) Glucose
- 4) Cellulose
Solution
Rayon is made from wood-pulp. The wood obtained from plants are made of cellulose.
Q25. 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.
Q26. 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.
Q27. Which of the following is not a property of plastics?
- 1) They are light.
- 2) They are relatively cheap.
- 3) They are not durable.
- 4) They are water proof.
Solution
Plastics are durable as they are strong and resistant to decay, rusting and chemical attack.
Q28. ________ is used in making parachutes.
Solution
Nylon is used in making parachutes.
Q29. PET is a very familiar form of polyester.
- 1) True
- 2) False
Solution
True
Q30. 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.
Q31. Rayon cannot be dyed in different colours.
- 1) True
- 2) False
Solution
False. Rayon can be dyed in different colours.
Q32. Bio-degradable substances are materials that:
- 1) Melt on heating
- 2) Are used as food for animals
- 3) Undergo natural decomposition by bacteria
- 4) Can grow
Solution
Bio-degradable substances are materials that get decomposed by microbial action.
Q33. Polymers can be both thermal and electrical _________.
Solution
Polymers can be both thermal and electrical insulators.
Q34. Thermoplastics become soft on heating and can bend easily.
- 1) True
- 2) False
Solution
True
Q35. Plastics cause environmental pollution as it releases greenhouse gases on burning.
- 1) True
- 2) False
Solution
True
Q36. Synthetic fibres ________ on burning.
Solution
Synthetic fibres melt on burning.
Q37. Rayon is first fully man-made fibre.
- 1) False
- 2) True
Solution
False. Nylon is first fully man-made fibre.
Q38. (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.
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.
Q39. Give four common uses of nylon fibres.
Solution
Nylon fibres are most often used for making stockings, tooth brushes, ropes and parachutes.
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. The waste created by plastics is environment friendly.
- 1) True
- 2) False
Solution
False. The waste created by plastics is hazardous to environment.
Q42. 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.
Q43. 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.
Q44. Synthetic polymers cause environmental pollution.
- 1) False
- 2) True
Solution
True
Q45. Which among the following is not a natural polymer?
- 1) Cotton
- 2) Silk
- 3) Wool
- 4) Nylon
Solution
Nylon is a synthetic (man-made) polymer.
Q46. 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.
Q47. Clothes made of ________ should be worn in kitchen.
Solution
Clothes made of natural fibres should be worn in kitchen.
Q48. Terylene is a typical ________ polymer.
Solution
Terylene is a typical polyester polymer.
Q49. 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.
Q50. 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.
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. 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.
Q53. 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.
Q54. Rayon was originally called _______.
Solution
Rayon was originally called artificial silk.
Q55. Plastic materials are _______.
Solution
Plastic materials are water proof.