The substances W is a fossil fuel. It occurs deep below the ground in certain areas of the earth. Another fossil fuel X is found trapped above the deposits of W. when W is subjected to a process called Y, then a number of different products are collected at different temperature ranges which are put to different uses. A special grade of product z obtained in this way is used an aviation fuel in jet aero planes.

(a) What are (i) W, and (ii) X

(b) what is the physical state of (i) W, and (ii) X?

(c) Name the process Y?

(d) Name the product Z?

(a) The substance W is Petroleum and substance Y is Natural gas. Natural gas is a fossil fuel other than coal and petroleum. Petroleum can be extracted with giant drilling machines. The layer containing petroleum oil and natural gas is above that of water.

(b) The physical state of W is a liquid. Petroleum is a dark oily liquid. It has an unpleasant odor. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.

The physical state of X is Gas. Natural gas is a fossil fuel other than coal and petroleum. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

(c) Process Y is known as Fractional distillation. It is the process of separation of a mixture into its components, by the difference in their boiling points. Mixture is heated which causes one or more components to vaporize at different temperatures. The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery.

(d) The product Z is Kerosene. Kerosene is one of the constituent of petroleum. It is a fossil fuel. It is used as a fuel for stoves, lamps and for jet aircrafts.