8th Science Guide Lesson 15 Chemistry in Everyday Life

8th Std Science Guide Lesson 15  Chemistry in Everyday Life | English Medium

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8th Science Guide Lesson 15 Chemistry in Everyday Life

I. Choose the best answer.

1. The chemical mixed with LPG that helps in the detection of its leakage is __________

1. methanol
2. ethanol
3. camphor
4. mercapton

Ans : mercapton

2. Which is known as syn gas?

1. Marsh gas
2. Water gas
3. Producer gas
4. Coal gas

Ans : Water gas

3. The unit of calorific value of fuel is __________

1. kilo joule per mole
2. kilo joule per gram
3. kilo joule per kilo gram
4. joule per kilo gram

Ans : kilo joule per kilo gram

4. __________ is the coal of superior quality.

1. Peat
2. Lignite
3. Bituminous
4. Anthracite

Ans : Anthracite

5. The main component of natural gas is __________

1. methane
2. ethane
3. propane
4. butane

Ans : methane

II. Fill in the blanks.

1. Producer gas is a mixture of __________ Ans : Carbon monoxide and 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.

1. Octane rating – Diesel
2. Cetane rating – Methane
3. Simplest hydrocarbon – Petrol
4. Peat – Bown in colour
5. Lignite – First stage coal

Ans : 1 – c, 2 – a, 3 – b, 4 – e, 5 – d

IV. Answer in brief:

1. What do you mean by catenation?

• Te property of carbon atom to form bonds with itself resulting in a single large structure or chain.

2. Mention the advantages of natural gas.

• It produces lot of heat as it is 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.

CNG – 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 as 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 is the highest grade coal.
• It is hard and dark black in colour.
• 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

6. Distinguish between octane number and cetane number.

7. Name the places in Tamilnadu harnessing wind energy from wind mills.

• Wind mills are mostly located at Kayathar, Aralvaimozhi, Palladam and Kudimangalam in Tamil Nadu.

8. Solar energy is a non depleting energy. Justify.

• Solar energy is the only viable fuel source of non depleting nature for, sun 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 the fossil fuel in order to meet the needs of the world.
• With the advancements in science and technology, solar energy has become more affordable, and it can overcome energy crisis. Solar energy is a clean energy.
• With the minimum efforts maximum energy can be harnessed using various equipments.

VIII. Answer in detail:

1. Explain the different types of coal.

Lignite

• Lignite is a brown colored coal of lowest grade.
• It has least content of carbon.
• 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 sulfur 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 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

• It is the highest grade coal. It is hard and dark black in colour.
• 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?

The products obtained from fractional distillation of petroleum are

• Liquefied petroleum gas
• Petrol & diesel
• Kerosene
• Lubricating oil
• Paraffin wax
• Bitumen
• Refinery Gas
• Naphtha
• Fuel Oil
• Chemical
• Jet Fuel

3. What are the different types of 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.