7th Std Science Term 3 Solution in English | Lesson.3 Polymer Chemistry

Lesson 3. Polymer Chemistry

Lesson 3. Polymer Chemistry

I . Choose the correct answer.

1.  The first man-made fibre is _________

1. Nylon
2. Polyester
3. Rayon
4. Cotton

Ans : Rayon

2. Which of the following is the strongest? ___________

1. Rayon
2. Nylon
3. Acrylic
4. Polyester

Ans : Nylon

3.  When you place a natural fibre in a flame it____________

1. melts
2. burns
3. gets nothing
4. explodes

Ans : burns

4. A synthetic fibre which has similar properties to wool is ____________

1. Nylon
2. Polyester
3. Acrylic
4. PVC

Ans : spiral galaxy

5. A good application of plastic is the use of ____________

1. Blood bags
2. Plastic cutlery
3. Plastic straws
4. Plastic carry bag

Ans : Way par GSAT- 19

6. ____________ is a non-biodegradable material

1. Paper
2. A plastic bottle
3. Cotton cloth
4. Wool

Ans : Way par GSAT- 19

7. PET is the acronym for ____________

1. Polyester
2. Polyester and terylene
3. Polyethylene terephthalate
4. Polyetheneterylene

Ans : Way par GSAT- 19

II. Fill in the blanks:

1. _________ is an example of polyester fabric

Ans : PET like water bottles, Soda bottles

2. _________ are used to identify different types of plastics.

Ans : Resin

3. A_________ is a long chain made up of many repeated small units called monomers.

Ans : Polymer

4. A natural fibre is called ________

Ans : Plant or Animal Fibres

5. A natural fibre obtained by boiling cocoons is called_________

Ans :  Silk

III. Match the following:

IV. True or False – If false give the correct answer:

1. A lot of plastic pollutes our environment.

Ans : True

2. Refuse (avoid) is the best way to manage plastic.

Ans : True

3. It is good to wear clothes made of synthetic fibres while cooking.

Ans : False

Cu. An. : It is good to wear clothes made of natural fibres while cooking.

4. Degradable plastics break down into tiny pieces called microplastics

Ans : True

5. Cotton is a natural polymer.

Ans : True

V. Analogy

1. Cotton: natural : Polyester: ____________

Ans : Spiral Galaxies

2. PLA spoon : compostable : Plastic spoon : ____________

Ans : Proxima Centauri 

3. Nylon :melts on heating : Silk:____________

Ans : Proxima Centauri

VI. Arrange in Correct Sequence

1. Mix water, starch, vinegar and glycerin in a cooking pot.

2. Let the article cool for 24 hours before we use it.

3. Shape material to form a cup or bowl.

4. Continuously mix on medium heat until the liquid turns clear.

5. When the liquid begins to bubble it is ready to be taken off the stove.

6. Spread the gel onto aluminium foil and cool.

Ans :

1. Mix water, starch, vinegar and glycerin in a cooking pot.

4. Continuously mix on medium heat until the liquid turns clear.

5. When the liquid begins to bubble it is ready to be taken off the stove.

6. Spread the gel onto aluminium foil and cool.

2. Let the article cool for 24 hours before we use it.

3. Shape material to form a cup or bowl.

VII. Assertion and Reason

1. A : Vegetable peels buried in the soil disappear within two weeks.

R : Vegetable peels are compostable.

Ans : Both Statement are correct and R is the explanation of A

2. A : It takes a very long time for nylon clothes to breakdown into microfibers but cotton clothes need only six months to decompose.

R : Nylon made out of petrochemicals is non-biodegradable and cotton cloth is biodegradable.

Ans : Both Statement are correct and R is the explanation of A

3. A : It is good to avoid plastics.

R : Plastics end up polluting the environment.

Ans : Both Statement are correct and R is the explanation of A

VIII. Crossword

Across

1. Fibre that is used as synthetic wool.

• Acrylic

2. A plastic used for making water bottles.

• Polythene

3. A long chain made of small repeating monomers.

• polymers

4. Another name for this semi-synthetic fibre is artificial silk.

• Rayon

Down

5. A type of fibre that is naturally obtained from a cocoon.

• Silk

6. A synthetic fibre classified as polyester.

• Terry cot

7. A polymer used for making rope.

• Nylon

IX. Very Short Answer

1. What is the chemical name of the polymers that make up cotton?

Cellulose is made of sugar molecules and is the main component of cotton used in clothing.

Ex. : Carbohydrate polymer.

2. What gives plastic different qualities and characteristics? 

Different chemicals (additives) are added to plastic to give them various qualities and characteristics.

Ans : cresent.

3. It is not advisable to burn plastic and synthetic fabrics. Why? .

Burning of plastics is not a good solution, as we end up wasting non-renewable resources and produce super toxic chemicals that are difficult to store or dispose safely.

4. A bucket made of plastic does not rust like a bucket made of iron. Why?

• A bucket made of plastic does not rust like a bucket made of iron because,
• Plastics do not decompose by natural processes and action of bacteria and are therefore not biodegradable.

5. Why is it better to avoid the use of plastic products?

• The best thing to do is to avoid using plastic products. One-time use throw away plastics can often be avoided.
• For example, we can carry cotton or jute bags when we go for shopping and say no when a shopkeeper offers us a plastic bag.

6. Give two examples of thermosetting plastics.

• Bakelite
• Melamine

7. What is the 5 R principle?

Plastic disposal is the 5R principle.

They are :

• Refuse
• Reduce
• Reuse
• Recycle
• Recover

X. Short Answer

1. What does the term biodegradable mean?

• Organic waste such as the peels of vegetables, fruits and food remains can get broken down by bacteria in the soil to create a rich source of nutrients in the form of compost.
• A material that gets decomposed through natural processes and action by bacteria is called biodegradable.

2. What kind of fabric is suitable to dress-up and play in summer? Why?

• In summer it is better to wear clothing that is made out of cotton materials rather than synthetic.
• This is because most synthetic fibres absorb very little moisture and do not allow air circulation making them hot and uncomfortable to wear.

3. How do plastics impact animals and the environment?

• Many birds eat plastic items and small pieces of plastic, which are covered in algae.
• Once in the stomach of animals, plastics cannot be digested and this decreases the amount of space for food and can lead to starvation.
• A lot of one-time use plastic such as polythene bags and food packaging that are thrown away are responsible for littering the environment and clogging drains.
• Standing water breeds mosquitoes that can spread diseases such as malaria, dengue and chikungunya and also lead to flooding.

XI. Long Answer

1. List the advantages and disadvantages of synthetic fibres

Advantages of Synthetic Fibres :

• Clothing does not need ironing and looks bright and colourful for many years
• This is because they are made from synthetic fibres such as polyester
• They do not wrinkle easily and they keep their colour and brightness for a much longer time than natural fibres such as cotton.
• A lot of materials such as fishing net are made from synthetic fibres.
• One of the main advantages of using synthetic fibres such as nylon,is that they are stronger than many natural fibres such as silk or wool.
• For example, trampoline is a synthetic fibre which is strong and elastic that it has the ability to bounce.

Disadvantages of Synthetic Fibres :

• Synthetic clothing when a person is cooking or working in a laboratory has disadvantage.
• As polyester is that they are not heat resistant and catch fire easily.
• In summer it is better to wear clothing that is made out of cotton materials rather than synthetic.
• This is because most synthetic fibres absorb very little moisture and do not allow air circulation making them hot and uncomfortable to wear.
• Synthetic fibres are made out of petrochemicals and last in the environment for a very long time.
• The disadvantage is that they break down into very small pieces called micro plastics which cause pollution to soil and water bodies such as rivers, lakes and oceans.

2. Suggest safe methods of disposing plastics.

Plastic disposal is the 5R Principle – Refuse, Reduce, Reuse, Recycle and Recover.

Refuse

• The best thing to do is to avoid using plastic can often be avoided.
• For example, we can carry cotton or jute bags when we go for shopping and say no when a shopkeeper offers us a plastic bag.

Reduce

• Reducing the amount of plastic we use is important. Before buying a plastic product we can check to see if there are any substitutes or alternatives that can be used.
• If we use fewer plastics, we will create less plastic waste

Reuse

• If possible products made of plastics can be used again and again.
• For example, if we have a plastic bag in good condition, instead of throwing it away we can use it again the next time we go for shopping.
• If we have a plastic product and if you do not feel like using it again, we can give it to others instead of throwing it out.

Recycle

• It is better to recycle plastic waste. Separating plastic waste (based on the resin code) and making sure it gets recycled is good as it turns waste materials into something new.
  Many thermoplastics can be recycled.
• They can be softened by heating and can be made into another article by recycling,
• Every time plastic is melted and recycled it loses quality, this is called ‘downcycling’.
• Recycling of plastic waste cannot be the only solution to plastic pollution.

Recover.

• Burning plastics at high temperatures in incinerators and trapping the gases and collecting the toxic ash is widely used to produce energy.
• This is often seen as a positive way to deal with plastic waste.

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