General Science Solutions Solutions for Class 6 Science Chapter 6 - Substances In Daily Use

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(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.

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Paper is manufactured by the following process:

• Logs of wood are made to pass through a debarker, where the barks of the tree are separated.
• Then the wood is chopped into small pieces and is mixed with some chemicals and water in digetser for the formation of the pulp.
• The obtained pulp is washed refined and sometimes even bleached.
• The pulp is made to travel down the screen to remove excess of water and then to the rollers where it is being dried and squeezed between large rollers to form rolls of paper. 

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a. We must use cotton clothes in summers because they protect us from the heat of the sun. They absorb sweat and help keep our bodies cool. The pores in cotton clothes allow the free movement of air, which helps cool our bodies.

b. We must observe economy in the use of materials because they directly or indirectly affect our environment. Most of the natural materials which we obtain from our environment are exhaustible/non renewable resources i.e. once these resources are finished they cannot be renewed again or even if they can, it would take several years to do so. For example, our forests from where we obtain wood are precious resources because once a forest is destroyed, it would take several years to renew that forest. Also, destroying the forests for our needs affects the habitat of several other species of organisms and plants. The man made materials which we use are largely non biodegradable for example plastic etc. Increased use of man made materials pose a threat to the environment because their disposal is not easy and leads to environmental pollution. These examples state the importance of judicious use of both natural and man made materials.

c. We very well know that paper is obtained from trees. Trees are important resources because they not only provide us with wood or paper but are also a habitat for various organisms. They are important in maintaining the climate as well. The more paper we use or waste, the more no. of trees will have to be cut down for this purpose, thus leading to v arious kinds of harmful effects on our environment. We should make a genuine effort in saving paper by adopting small steps which can make a huge difference.

d. Man made materials have more demand because of their characteristics like easy to use, low cost of production, cheaper products and variety of things which can be made from them.

e. Humus is a natural material because its formation is a natural process. It is the dark-coloured layer of top soil that is rich in nutrients. The decomposers convert the dead plants and animals into humus that is utilised by the plants. It increases the fertility of the soil.

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