Friday, August 10, 2012

CBSE 8th Science Ch.5.Coal and Petroleum Solved questions

CBSE Class VIII (8th) Science | Chapter 5. COAL AND PETROLEUM
Q. What is Fuel?
Ans: Substances that burn in air to give heat energy are called fuels.
Q. What is Fossil Fuels?
Ans: A Naturally occurring substances that are extracted from the earth crust and also used as fuels is called Fossil Fuels like Coal, crude oil and natural gas.
Q.What is different types of coal?
Ans: 1. Lignite (Brown Coal) contains 25 – 35 % carbon.
2. Bituminous coal (Soft coal)  contains 45 – 86 % carbon.
3. Anthracite coal (Hard coal - It has the highest heat energy) contain 87 – 97%carbon.
Q. How coal is formed ?
Ans: Coal is formed by degradation of wood under the influence of high pressure and temperature over millions of years is called carbonization.
Q. What is destrictive distillation of coal?
Ans: When coal is heated in the absence of air is called destructive distillation of coal.
Q. What are the different products obtain from destructive distillation of coal?
Different products
1. Coal Gas - main constituent are H2,CH4 and CO
As a fuel in cooking food , street lighting
2. Liquid Ammonia
To make fertilizers
3. Gas Carbon
Carbon electrodes in batteries
4. Coke(grayish Black)
As a fuel and as a reducing agent in steel manufacturing,
Produce fuel gas like water gas (CO+H2) and Producer gas(CO+N2)  
For producing Carbide like CaC2,SiC , and Al4C3
5. Coal Tar (black Terry material)
To make plastics, paints,  dyes, naphthalene balls and explosives, Perfumes
Q. What do you mean by  fractional distillation?
Ans: The process of heating a mixture of many liquids having different boiling points and separating them by cooling is called fractional distillation.
Q. How Petroleum and Natural Gas are formed?
Ans: Dead plants and animals buried at the bottom of the sea millions of years ago. They got covered with layers of sand and clay. Due to high pressure and temperature, they got transformed into petroleum.
Petroleum is obtained by drilling through the earth. The crude oil is pumped out from a well as a black liquid.
Q. How do various constituents  of petroleum is separated?
Ans:  Various constituents of petroleum are separated by fractional distillation in fractionating  columns is known as refining of petroleum. The various fractions of petroleum obtained are
Petroleum Gas
Fuel for home (LPG)
Motor fuel
Fuel for stove and jet aircrafts.
Fuel for heavy motor vehicles.
Lubricating oil
Fuel Oil
Fuel for Power Stations and Ship
Paraffin wax
Candles, Vaseline
Paints, road surfacing
Q. How is natural gas formed?
Ans: Natural gas is formed whenever vegetation decomposes in marshes, sewage and in coal or petroleum mines. It is made up of 90 % methane.
Q.What are the main uses of Natural gas
Ans: (a) it is used for producing H2 gas by heating 1250k .
(b) For manufacturing Carbon black that is used in rubber industry as reinforcing agent to make tyre.
(c) For manufacturing Petrochemical and fertilizer
Q. Why natural gas is called an ideal fuel?
Ans:  It is an ideal fuel because
 (a) Burn with smoke less flame
(b) Do not leave ash
(c) Having high calorific value about 55kgJ/g

1 comment:

J Sunil said...

8th science: Ch:Reaching the age of adolescence solved questions

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