Substances in Daily Use | Class 6 | Science | Chapter 6 | Maharashtra State Board
In this educational video, we will discuss substances and objects that we use in our daily lives. We will learn that there are two types of substances: natural substances and man-made substances. Natural substances are further classified into biotic and abiotic substances. Next, we will explore the production of various substances, such as rubber, paper, and synthetic fibers or threads. We will demonstrate the process of vulcanization of rubber and the manufacturing of paper. We will also examine synthetic fibers or threads, including nylon, rayon, dacron, terylene, and terene, in detail. Finally, we will discuss the advantages and disadvantages of synthetic fibers, highlighting their strengths and weaknesses. By the end of this lesson, you will have a better understanding of the different types of substances, their production processes, and their uses in daily life.
Questions & Answers
1. Fill in the blanks using proper words.
Rubber made by vulcanization is a hard material.
Man-made materials are made by processing natural materials.
Nylon thread was developed simultaneously in New York and London.
Rayon is also known as synthetic silk.
2. Answer the following questions.
(a) Why did the need for man-made materials arise?
Ans. The need for man-made materials arose due to the following reasons:
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. Leather, jute, wool, cotton, silk are the natural substances obtained from plants and animals.
(c) What is vulcanization?
Ans. Vulcanization is the process in which rubber is heated with sulphur for three to four hours. Sulphur is mixed to give hardness to rubber. The proportion of sulphur depends on the purpose for which the rubber is to 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.
3. What are we used for?
(a) Soil -
Ans. Soil supports plant life and hence indirectly supports all living things. It is used for making clay pot, utensils, bricks etc.
(b) Wood -
Ans. Wood is used in paper industry. It is also used to make furniture.
(c) Nylon -
Ans. Nylon is used to manufacture clothes, fishing nets, ropes, etc.
(d) Paper -
Ans. Paper is used in our textbooks, note books, currency notes, etc.
(e) Rubber -
Ans. Rubber is used in the manufacture of erasers, tyres, rubber toys, rubber bands, etc.
4. How is paper manufactured? Write in your own words.
Ans.
Coniferous trees like pine trees 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 with some chemicals is kept soaked for a long time to form pulp.
On completion of chemical process, 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. During summer we sweat more due to high temperature. Cotton clothes absorb sweat. Synthetic clothes are water repellent. They do not absorb sweat and we feel uncomfortable. Hence, 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 to fulfil their needs; they are getting depleted at a faster rate. At the same time, it takes a very long time for these substances to get naturally formed again. Hence, we must observe economy in the use of materials so that they are available for the future generation also.
(c) Saving paper is the need of the hour.
Ans. Saving paper means saving trees as wood is used as the raw material to manufacture paper. Trees are natural habitat for many Living things. Trees help in increasing rainfall and water availability. Hence, saving paper helps in saving trees which in turn maintains balance in nature.
(d) Man-made materials have more demand.
Ans. Man-made substances are waterproof, lightweight and easy for transportation. Substances in Daily Use. They are easier to use and can be made available in plenty at a low cost. Hence, there is more demand for man-made materials.
(e) Humus is a natural material.
Ans. Humus is obtained from plant and animal wastes. Micro-organisms act on these wastes and convert them into humus. Hence, humus is a natural material.
6. Find out.
(1) How is lac obtained from nature?
Ans. Lac is a resinous substance secreted from the glands present in the skin of female lac insect. Lac insects live on the Palash trees. In India lac is mainly produced in the states of Rajasthan and Bihar.
(2) How are pearls obtained?
Ans. Pearls are formed when a foreign particle such as a grain of sand or a small particle of rock accidentally enters the space between the mantle and shell of an oyster’s body.
Oysters cannot reject the particle, and as a defence mechanism it produces a shining coating called nacre on the particle layer by layer.
As the shiny layers get added, a pearl is formed.
Cultured pearls are artificially formed by inserting a bead in oyster shell and allowed to coat it with nacre over several years.
E X T R A
1. Fill in the blanks using proper words.
Natural rubber is obtained from latex of trees.
Changes where the original constituent substances cannot be obtained again from the new substances are called irreversible changes.
A paper factory in Maharashtra is situated at Ballarpur .
Glass can be made from sand and calcium .
Botanical name of rubber plant is Hevea brasiliensis .
Hydrocarbons obtained from mineral oils are used to make polymer chains.
The maximum production of rubber in India is in Kerala .
Charles Goodyear invented the process of vulcanisation.
2. Answer the following in one or two sentences.
(a) Why was Rayon named so?
Ans. The threads of Rayon have shine and strength. They appeared to be shining bright like the sun’s rays. Hence, they were named ‘Rayon.
(b) How are TV sets, refrigerators, etc. packed? Why?
Ans. To pack TV sets, refrigerators, etc. big cartons and thermocol are used. These man-made substances are water resistant, light weight and easy for transportation.
(c) Where was the process of making paper invented?
Ans. The process of making paper was invented in China.
(d) Give the properties and uses of nylon.
Ans. Nylon threads have a shine and are strong, transparent and water resistant. They are used to manufacture clothes, fishing nets, ropes, etc.
(e) What is latex?
Ans. Latex is a milky white natural substance produced in the stems of rubber trees.
(f) What kind of paper is used for currency notes manufacturing?
Ans. Flax fibre is used in the manufacture of currency notes.
3. Answer in brief.
(a) What are the advantages of synthetic fibre?
Ans. Advantages of synthetic fibre are:
These fibres can be manufactured on a large scale.
They cost less.
They are strong and durable.
They can be used for a long time.
They are water repellent. They dry easily.
They are light weight and comfortable to wear.
Clothes made from these threads are wrinkle free and scratch free.
(b) Give the shortcomings of synthetic fibre.
Ans. Shortcomings of synthetic fibre are:
They are water repellent. Hence, they do not absorb sweat from the skin.
Continuous use of these clothes keeps the skin moist which may cause skin diseases.
Synthetic clothes are uncomfortable to wear especially in summer.
They catch fire easily.
If they catch fire, they stick to the skin and cause skin injuries.
These fibres are not decomposed by micro-organisms.
(c) Write a short note on natural rubber.
Ans. Rubber is a natural substance obtained by collecting the latex of certain trees. The botanical name of this tree is ‘Hevea brasiliensis’. In India, the maximum production of rubber is in Kerala.
(d) What are dacron, terylene and terene?
Ans. Dacron, terelyne and terene are synthetic fibres prepared from hydrocarbons.
Various hydrocarbons obtained from mineral oil are used to make polymer chains.
A solution of such polymer is pressed through a strainer with fine holes.
The fibre formed after cooling are long and unbroken threads.
These threads have been named as dacron, terylene and terene.
(e) Why natural substances are depleting?
Ans. Due to increase in population, there is an increase in demand. To meet this demand, natural substances are used to a greater extent.
Due to human nature to make his life more comfortable, he learnt to use natural resources and also began to process them to make new substances. Hence, natural substances are depleting at an alarming rate.
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