Substances in Daily Use Q & A
Q.1. Fill in the blanks using proper works:
(a) Rubber made by vulcanization is a hard 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 .
Q.2. Answer the following questions.
(a) Why did the need for man-made materials arise?
Ans: The need for man-made materials arose :
- To meet the needs of an increasing population.
- Human nature to try to make life more comfortable.
- They can be made available in plenty at a low cost.
- The reserve of natural substances is decreasing.
(b) Which are the natural materials obtained from plants and animals?
Ans: The natural substances obtained from plants and animals are leather, jute, wool, cotton, silk.
(c) What is vulcanization?
Ans: Vulcanization is the process of making rubber. In this process the rubber is heated with sulphur for three to four hours.To give hardness to the rubber, the sulphur is mixed in it and the proportion of the sulphur is determined by the purpose which the rubber will be used.
(d) Which natural materials are used to obtain fibres?
Ans: Cotton, wood pulp and various hydrocarbons obtained from mineral oils are used to obtain fibres.
Q.3. What are we used for?
- Soil
Ans: Soil is used to support plant life and all living things and used for making clay pot, utensils, bricks etc.
- Wood
Ans: Wood is used in paper industry and also used to make furniture.
- Nylon
Ans: Nylon is used to manufacture clothes, fishing nets, ropes, etc.
- Paper
Ans: Paper is used in our textbooks, note books, currency notes, etc.
- Rubber
Ans: Rubber is used in manufacturing erasers, tyres, rubber toys, rubber bands, etc.
Q.4. How is paper manufactured? Write in your own words.
Ans: The paper is manufactured by using trees.
Q.5. Give scientific reasons.
- We must use cotton clothes during summer.
Ans: During summer we sweat more because of high temperature and cotton clothes absorb sweat but synthetic clothes are water repellent so they don’t absorb sweat and we feel uncomfortable that’s why we must use cotton clothes in summer.
(b) We must observe economy in the use of materials.
Ans: Due to excessive use of natural substances by human beings.
(c) Saving paper is the need of the hour.
Ans: Saving paper means saving trees because wood is used as the raw material to manufacture paper.Trees are natural habitat for many Living things, they help in increasing rainfall and water availability, they give us oxygen.That’s why, saving paper helps in saving trees which in turn maintains balance in nature.
(d) Man-made materials have more demand.
Ans: Man-made materials have more demand because they are easy to use and they can be made available in plenty at a low cost.
(e) Humus is a natural material.
Ans: Humus is a natural material because its formation is a natural process. it is obtained from plant and animal wastes and micro-organisms act on these wastes and convert them into humus.That’s why, humus is a natural material.
Q.6. Find out.
(1) How is lac obtained from nature?
(2) How are pearls obtained?