Chapter 17 - Man made Materials
1. Try to find it.
a. Plastic shows …… property, hence it can be moulded to any shape.
Ans: plasticity
b. Motor cars are coated with …….
Ans: Teflon
c. Thermocol melts at …… ºC.
Ans: more than 100
d. …… glass dissolves in water.
Ans: Alkali Silicate
2. Who is my partner?
| ‘A’ column | ‘B’ column |
|---|---|
a. Lead glass | i. Plates |
b. Bakelite | ii. Mattresses |
c. Thermocol | iii. Electric bulb |
d. Optic glass | iv. Electric switch |
e. Polypropylene | v. Lens |
Ans:
| ‘A’ column | ‘B’ column |
|---|---|
a. Lead glass | iii. Electric bulb |
b. Bakelite | iv. Electric switch |
c. Thermocol | i. Plates |
d. Optic glass | v. Lens |
e. Polypropylene | ii. Mattresses |
3. Answer the following.
a. Thermocol is produced from which material?
Ans: Thermocol is produced from a thermoplastic material called polystyrene.
b. Write uses of PVC.
Ans: PVC is used for manufacture of bottles, raincoats, pipes, shoes, furniture, ropes, toys, handbags, electric cable insulation, etc.
c. Write the natural or manmade raw material of the following items.
Mattress, glass vessel, bangle, chair, gunny bag, broom, knife, pen.
Ans:
| Evergreen forests | Grasslands |
|---|---|
(i) Evergreen forests are found in the areas where it rains throughout the year. | (i) Grasslands are found in the areas where the rainfall is not enough to support the growth of big trees. |
(ii) The forests are dense and trees compete amongst themselves to get sunlight, thus growing tall. | (ii) Extensive growth of grass is seen however, very few trees and shrubs are also found. |
(iii) The leaves of trees in this forest are broad and green. | (iii) Grassland plants have thin, narrow leaves to reduce transpiration (evaporation). |
(iv) Evergreen forest trees do not shed their leaves completely regardless of the season. | (iv) Grasslands dry during dormant season (period in which growth ceases temporary.) |
d. Which are the main ingredients of glass?
Ans: The main ingredients of glass include sand (silica), soda, limestone, and a small quantity of magnesium oxide.
e. How is the plastic produced?
Ans:
(i) Plastics are produced from natural, organic materials such as cellulose, coal, natural gas, crude oil, etc.
(ii) The production of plastics starts with the distillation of crude oil in an oil refinery.
(iii) The distillation process separates the heavier fraction of crude oil from its lighter fractions.
(iv) One of the fractions, naphtha, is crucial for the production of plastic.
(v) There are two main processes to produce plastics: addition and condensation polymerization, both of which require some additives called catalysts.
(vi) In a polymerization reaction, small units called monomers are linked together to form long polymer chains.
(vii) These are then melted, cooled, and converted into small pellets.
(viii) These pellets are then processed using methods such as extrusion and injection molding. blow molding, rotational molding, etc. to form the required plastic products.
a. Extrusion: This method is used to make plastic films.
b. Injection molding: This method is used to make plastic containers.
c. Blow molding: This method is used to make plastic bottles.
d. Rotational molding: This method is used to make large, hollow items like toys, furniture, tanks, etc.
4. Distinguish between.
a. Man made material and natural material
Ans:
| Man Made material | Natural material |
|---|---|
(i) The materials manufactured by human beings after performing successful research on various natural materials for use in daily life are called manmade materials. | (i) The materials provided by nature and which can be used in our daily life as such or by little modifications are called natural materials. |
(ii) Manmade materials are usually non-biodegradable.
eg. Plastic, glass, thermocol, etc. | (ii) Natural materials are biodegradable.
eg. Jute, paper, cloth, wood, etc. |
Examples are plastic, glass, thermocol, etc. | Examples are jute, paper, cloth, wood, etc. |
b. Thermoplastic and thermosetting plastic.
Ans:
| Thermoplastic | Thermosetting plastic |
|---|---|
(i) A thermoplastic is a plastic that can be moulded into the desired shape and remoulded after heating. | (i) A thermosetting plastic is one that cannot be remoulded after being heated and given a specific shape. |
(ii) This type of plastic can be remoulded and recycled. | (ii) This type of plastic cannot be remoulded.polyurethane, and polyester. |
(iii) It is used in the preparation of bottles, milk bags, pipes, handbags, shoes, etc. | (iii) It is used in the preparation of cooker handles, insulating coverings, electric switches, fiberglass, etc. |
Examples are polyvinyl chloride, polystyrene, polyethylene, and polypropylene. | Examples are bakelite, melamine, polyurethane, and polyester. |
5. Answer the following in your own words.
a. Explain the effect and remedial plans of following materials on environment and human health.
1. Plastic
Ans:
(i) Plastic is a non-degradable material, and hence, it acts as an environmental pollutant.
(ii) If plastic materials are thrown out in the open, they can clog the drainage system.
(iii) When plastic materials are thrown in grasslands, grazing animals might consume those materials, thereby suffocating them to death.
(iv) Plastic materials on fire emit harmful greenhouse gases like sulphur dioxide, nitrogen dioxide, etc.
(v) If plastics are dumped into water bodies, it pollutes the water and destroys the marine habitat.
(vi) Materials on fire emit harmful greenhouse gases like sulphur dioxide, nitrogen dioxide, etc.
(vii) If plastic is dumped in landfills, it remains the same for thousands of years.
2. Glass:
Ans:
(i) Glass is a non-degradable material, and hence, it acts as an environmental pollutant.
(ii) The process of making glass requires a very high temperature (1500 °C) for the melting of raw materials. In this process, harmful greenhouse gases such as carbon dioxide, sulphur dioxide, nitrogen dioxide, etc. are emitted.
(iii) Pieces of waste glass material, when flown into a water body, affect the water ecosystem and, on consumption, may choke aquatic animals to death.
(iv) Drainage may also get blocked due to pieces of waste glass.
3. Thermocol:
Ans:
(i) Thermocol is a non-degradable material and, hence, acts as an environmental pollutant.
(ii) People who are exposed to thermocol for an extended period of time may develop blood cancers such as leukaemia and lymphoma.
(iii) Over time, people working in thermocol production factories may develop problems with their eyes, skin, respiratory system, digestive system, etc.
(iv) Liquid styrene may cause skin burns.
(v) Thermocol plates and cups used to offer food, tea, water, etc., if reheated, may cause styrene (in the thermocol) to dissolve in that food. This may lead to severe health issues.
(vi) The burning of thermocol releases several poisonous gases into the atmosphere, the inhalation of which may cause severe respiratory problems.
b. Which measures will you arrange to minimize the environmental problems arising due to non-degradable plastic?
Ans:
(i) To reduce environmental pollution, the 4R principle must be followed by every responsible citizen. It includes:
a. Reduce: Minimum usage of non-degradable materials
b. Reuse: repeated usage of non-degradable materials
c. Recycle: Repeated usage of materials after proper processing
d. Recover: converting waste into resources (such as fuel, heat, electricity, etc.) through thermal and biological means. It is usually done after attempting to reduce, reuse, and recycle.
(ii) Some of the plastic items that can be replaced by degradable material include the following:
a. Plastic carry bags can be replaced by jute, paper, or cloth bags.
b. Milk pouches can be replaced by using tetrapackets.
c. Food wraps made out of beeswax-coated cotton material can be used. They are reusable and biodegradable, too.
d. Melamine cutlery can be replaced by those made out of cornstarch, and they are highly durable too.
6. Write short notes.
a. Glass production.
Ans:
(i) Glass is a non-crystalline and hard solid material formed mainly from a mixture of silica and silicate.
(ii) Primarily, a mixture of sand, soda, limestone, and a small quantity of magnesium oxide is heated in a furnace.
(iii) Sand, which is chemically silicon dioxide, melts at 1700 °C.
(iv) This temperature is extremely high; hence, pieces of discarded glass are added to the mixture to melt it at a lower temperature, i.e., at 850 °C.
(v) When all the ingredients of the mixture are liquefied, it is heated up to 1500 °C and then suddenly cooled.
(vi) This rapid cooling of the mixture leads to the formation of a homogeneous, amorphous, and transparent material called glass.
b. Optic glass
Ans:
(i) Optic glass or optical glass is produced from a mixture of sand, soda, limestone, barium oxide, and boron.
(ii) Optical glass is a type of pure glass of high quality.
Uses:
(i) It is useful for the production of spectacle lenses, microscopic lenses, etc.
(ii) It is also used for making lenses used in cameras, telescopes, and glass prisms.
3. Uses of plastic.
Ans:
(i) Plastic is used in the healthcare sector, e.g., syringes.
(ii) The vessels used to cook food in a microwave oven are made of plastic.
(iii) Vehicles are coated with Teflon to protect from scratches. Teflon is a type of plastic.
(iv) There are more than 2000 different types of plastic.
(v) Some types of plastic are used in assembling some parts of an aeroplane.
(vi) Polyacrylic is a type of plastic used for manufacturing lenses and artificial teeth.