Answer the Questions given in the worksheet pdf given below
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Answers
1) Some fibres are called synthetic fibres because they are made by man using chemicals.
2) Nylon is a man-made fibres made from coal,water and air. A nylon thread is actually stronger than a steel wire. The following examples indicate that nylon fibres are very strong
Nylon is used in making parachutes.
it is used in making ropes for rock climbing.
It is used in making sport accessories like rackets.
It is used in making ropes of boats.
It is used for making fishing nets,seat belts,etc.
3)Plastic containers are favoured for storing food due to the following reasons :
Plastic containers are lightweight.
They do not react with the food items and so safer to store unlike aluminium which reacts with lemon pickles.
It has good strength,durability and quality.
4) thermosetting plastic
Thermosetting plastics cannot be easily bent. If forced to bend, they will break.
Do not soften on heating
Cannot be moulded and reshaped
Cheaper
Not recyclable
hard and strong
It is used in making handles of cooking utensils.
Example: bakelite and melamine.
thermoplastic
Thermoplastic can be easily bent.
Softens on heating
Can be moulded and reshaped
Expensive
Recyclable
Soft and weak
It is used in making toys,combs and various containers
Example: Polythene and PVC.
5.(a) the handles of a saucepan are made of thermosetting plastic because it is a bad conductor of heat and does not get heated up while cooking.
(b) Electric plugs/ switches/ plug boards are saucepan is made of thermosetting plastic because it is a bad conductor of electricity.
6.Recyclable: Toys, carry boys, cooker handles, ball point pen, plastic chairs, electric wire Rest can't be recycled.
7.Rana should buy a cotton shirt for the summer and not a synthetic shirt. Cotton is a good absorber of water. So it can soak the sweat coming out of the body and expose it to the environment. Thus, it helps in evaporating the sweat and helps in cooling our body.
8.Plastics are non-corrosive in nature even if they come in contact with strong chemicals which is because of their non-reactive nature with most of the materials. For example, the cleaning chemicals that we use at home are stored in plastic bottles, instead of metal containers.
9.No, the handle and bristles of a toothbrush cannot be made of the same material. This is because the handle has to be hard and strong while bristles have to be soft and flexible.
10.Plastics should not be used for the following reasons:-
They are non biodegradable and take several years to decompose.
It adds to the pollution in the environment.
By burning plastics, poisonous gases are released that cause air pollution.
Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily.
11.Yes, 'manufacturing synthetic fibres is actually helping conservation of forests'. As synthetic fibres are obtained from petrochemicals, they have very well substituted the use of natural fibres like cotton, silk, wool and jute which are obtained from plants and animals.
12.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 (as shown in the figure below). After setting the experiment switch on the current, you will observe that 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.
13.Natural fibre: Fibres obtained from natural sources like plants and animals are called natural fibres. Examples: Cotton, Silk, Wool, Jute .
14.Meetu is the answer as Cotton gets evaporated easily.
B.
1) (b) it is obtained from wood pulp
2) (c) polyamine
3. (b) Teflon.
4. (b). bakelite
C.
1. man-made or artificial fibres.
2.petrochemicals
3.polymer
4.insulators
5.polymerization
D.
(i) Polyester (d) Fabrics do not wrinkle easily
(ii) Teflon (c) Used to make non-stick cookware
(iii) Rayon (a) Prepared by using wood pulp
(iv) Nylon (b) Used for making parachutes and stockings.
1. true
2. true
3. true
4. true