YADNYA e-Learning
Science Studies - 6th Standard
6. Substances in Daily Use
Question And Answer
1. Fill in the blanks using proper words.
(a) Rubber made by vulcanization is a man-made material.
(b) Man-made materials are made by processing natural materials.
(c) Nylon thread was developed simultaneously in New York and London.
(d) Rayon is also known as synthetic silk.
2. Answer the following questions.
(a) Why did the need for man-made materials arise ?
Ans: For several years, human have been dependent on natural materials to meet their demands. However there has been a shift towards the use of man-made materials as well. Increasing population, deforestation and limited natural resources are some of the reasons due to which the need for man-made materials arise.
(b) Which are the natural materials obtained from plants and animals ?
Ans: Leather and wool are obtained from animals and jute and cotton are obtained from plants.
(c) What is vulcanization ?
Ans: Vulcanization is the process carried out for the production of rubber. In this process, rubber is heated with sulphur for three to four hours. To give hardness to the rubber, sulphur is mixed in it. The proportion of sulphur in the mixture is determined by the purpose for which the rubber will be used.
(d) Which natural materials are used to obtain fibres ?
Ans: Wool and silk are natural materials of animal origin which are used for obtaining fibres. Cotton and jute examples of natural materials of plant origin which are used for obtaining fibres.
3. What are we used for ?
(a) Soil
Ans: construction, medicine and cosmetics.
(b) Wood
Ans: Making furniture, as a source of fuel, musical instruments, wooden toys
(c) Nylon
Ans: Tents, sleeping bags, rope, tennis strings, fishing nets
(d) Paper
Ans: envelopes, notebooks, packaging purpose etc.
(e) Rubber
Ans: Balloons, erasers, rubber toys, rubber balls etc.
4. How is paper manufactured ? Write in your own words.
Ans: Coniferous trees like pine are used to make paper. The bark of the logs of these trees is first removed and the wood is broken into small pieces. The mixture of these pieces and some chemical process is completed, the fibrous substances from wood pulp are separated, and some dyes are added. The pulp is then passed through rollers, dried to form paper and finally wound on reels.
5. Give scientific reasons.
(a) We must use cotton clothes in summer.
Ans: They are light weighted and comfortable. They do not absorb light. The sweat is observed in this fibres does skin infection is prevented.
(b) We must observe economy in the use of materials.
Ans: To save our natural resources and prevent its depletion we must observe economy in the use of materials.
(c) Saving paper is the need of the hour.
Ans: Paper and wood are closely related. For making paper many trees undergo cutting. To save trees and to prevent large scale deforestation. It is necessary to use paper sparingly.
(d) Man-made materials have more demand.
Ans: Man made substances are easier to use and can be made available in plenty at a low cost. Therefore man-made materials have more demand.
(e) Humus is a natural material.
Ans: Humus is the dark organic matter that forms in the soil when plant and animal matter the case. Thus, humus is a natural material.
6. Find out.
(1) How is lac obtained from nature ?
Ans: Lac is the scalar resinous of a number of species of lac insect. Cultivation begins when a farmer gets a stick that contains eggs ready to hatch and ties it to the tree to be infested. Thousands of lac insects colonize the branches of host tree and secrete the resinous pigment. The coated branches of the host trees are cut and harvested.
(2) How are pearls obtained ?
Ans: Pearls are formed inside the cells of bivalve marine animal. If any foreign particles enters the body of these animal a layer of protective substance called the chancre is deposited around it. This protective layer forms pearls.
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