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VIII SCIENCE - CHEMISTRY IN EVERYDAY LIFE- ANSWERS FOR TEXTBOOK EXERCISES
CHEMISTRY IN EVERYDAY LIFE
TEXTBOOK EXERCISES
I. Choose the best answer.
1. The chemical mixed with LPG that helps in the detection of its leakage is __________
a. methanol
b. ethanol
c. camphor
d. Mercaptan
Ans: d. Mercaptan
2. Which is known as syn gas?
a. Marsh gas
b. Water gas
c. Producer gas
d. Coal gas
Ans: b. Water gas
3. The unit of calorific value of fuel is__________
a. KJmol-1
b. KJg-1
c. KJkg-1
d. Jkg-1
Ans: c. KJkg-1
4. _____________ is the coal of superior quality.
a. Peat
b. Lignite
c. Bituminous
d. Anthracite
Ans: d. Anthracite
5. The main component of natural gas is __________
a. methane
b. ethane
c. propane
d. Butane
Ans: a. methane
II. Fill in the blanks.
1. Producer gas is a mixture of _______ and _______
Ans: Carbon monoxide, Nitrogen
2. __________ is known as marsh gas.
Ans: Methane
3. The term petroleum means __________
Ans: Rock oil
4. Heating coal in the absence of air is called __________
Ans: destructive distillation
5. An example for fossil fuel is __________
Ans: coal.
III. Match the following.
Ans:
IV. Answer briefly.
1. What do you mean by catenation?
The property of a carbon atom to form bonds with itself resulting in a single large structure or chain is called catenation.
2. Mention the advantages of natural gas.
The advantages of natural gas:
◼️ It produces lot of heat as it can be easily burnt.
◼️ It does not leave any residue.
◼️ It burns without smoke and so causes no pollution.
◼️ This can be easily supplied through pipes.
◼️ It can be directly used as fuel in homes and industries.
3. Expand CNG. List out its uses.
Expansion of CNG is Compressed Natural Gas.
When the natural gas is compressed at high pressure, it is called Compressed Natural Gas.
◼️ It is the cheapest and cleanest fuel.
◼️ Vehicles using this gas produce less carbon dioxide and hydrocarbon emission.
◼️ It is less expensive than petrol and diesel
4. Identify the gas known as syngas. Why is it called so?
Water gas is called syngas or synthesis gas.
Because, it is used to synthesize methanol and simple hydrocarbons.
It is used as an industrial fuel also.
5. Anthracite is known as the highest grade coal. Give reason.
◼️ Anthracite coal has a very light weight and the highest heat content.
◼️ It is very hard, deep black and shiny.
◼️ It contains 86-97% carbon and has a heating value slightly higher than bituminous coal.
◼️ It burns longer with more heat and less dust.
6. Distinguish between octane number and cetane number.
7. Name the places in Tamilnadu harnessing wind energy from windmills.
Wind mills located in Tamil Nadu are
Kayathar,
Aralvaimozhi,
Palladam and
Kudimangalam.
8. Solar energy is a non depleting energy. Justify.
◼️ Solar energy is the only viable fuel source of non depleting nature for the sun and provides a free and renewable source of energy.
◼️ It is the renewable type of energy without endangering the environment.
◼️ It is the potential source to replace fossil fuel in order to meet the needs of the world.
◼️ Solar energy is clean energy.
V. Answer in detail.
1. Explain the different types of coal.
Types of Coal Coal is classified into four main categories based on the amounts of carbon it contains and the heat energy it can produce.
They are;
Lignite
-Lignite is a brown colored coal of lowest grade.
-It has the lowest carbon content.
-The carbon content of lignite is 25 – 35%.
-Lignite contains a high amount of water and makes up almost half of our total coal reserves.
-It is used for electricity generation.
-The other uses include generating synthetic natural gas and producing fertilizer products.
Sub-bituminous
-When lignite becomes darker and harder over time sub-bituminous coal is formed.
-Sub bituminous coal is a black and dull coal.
-It has higher heating value than lignite and contains 35-44% carbon.
-It is used primarily as fuel for electricity power generation.
-This coal has lower sulphur content than other types and burns cleaner.
Bituminous
-With more chemical and physical changes, sub-bituminous coal is developed into bituminous coal.
-Bituminous coal is dark and hard.
-It contains 45-86% carbon. It has a high heating value.
-It is used to generate electricity.
-Other important use of this coal is to provide coke to iron and steel industries. -By-products of this coal can be converted into different chemicals which are used to make paint, nylon, and many other items.
Anthracite
-Anthracite is the highest grade coal.
-It has a very light weight and the highest heat content.
-Anthracite coal is very hard, deep black and shiny.
-It contains 86-97% carbon and has a heating value slightly higher than bituminous coal.
-It burns longer with more heat and less dust.
2. What is known as destructive distillation? Write about the products obtained from fractional distillation of petroleum.
Destructive distillation:
Coal when heated in the absence of air does not burn but produces many by-products. This process of heating coal in the absence of air is called destructive distillation.
The products obtained from fractional distillation of petroleum are;
◼️ Liquefied Petroleum Gas
◼️ Diesel and petrol
◼️ Kerosene
◼️ Lubricating oil
◼️ Paraffin wax
◼️ Bitumen
◼️ Refinery Gas
◼️ Naphtha
◼️ Fuel Oil
◼️ Chemicals
◼️ Jet fuel
3. Explain the different types of fuel gases
Fuels are classified into different types according to their physical state. They are classified into solid, liquid and gaseous fuels.
Solid fuels
Fuels like wood and coal are in solid state and they are called solid fuels. This type of fuel was the first one to be used by man. These fuels are easy to store and transport. The production cost is also very low.
Liquid fuels
Most of the liquid fuels are derived from the fossil remains of dead plants and animals. Petroleum oil, coal tar and alcohol are some of the liquid fuels. These fuels give more energy on burning and burn without ash.
Gaseous fuel
Coal gas, oil gas, producer gas and hydrogen are some of the gaseous fuels. These fuels can be easily transported through pipes and they do not produce pollution.
