Question

A hard material X which is mined from the earth is used as a household fuel and also for the generation of electricity at Thermal Power Stations. A soft material Y is also used as a fuel in the form of candles. A gaseous material Z which occurs alongwith petroleum is increasingly being used as a fuel in running vehicles in its compressed form.
(a) What are materials, X, Y and Z?
(b) When materials X, Y and Z are burned separately:
(1) When material burns by producing a yellow, luminous flame?
(2) Which material ultimately burns without producing a flame?
(3) Which material can burn in a gas stove by producing a blue flame?

Answer 1

(a) The hard material, X, mined from the Earth and used in the generation of electricity is coal. The soft material, Y, used as a fuel in the form of candles is wax. The gaseous material, Z, occurring along with petroleum and increasingly used as a vehicular fuel in its compressed form is natural gas.

(b) (1) Wax burns by producing a yellow, luminous flame due to incomplete combustion. This is because oxygen doesn't get a proper way to get into the wax vapour to burn it completely.

(2) Coal ultimately burns without producing a flame. It comprises some volatile substances that burn with a flame, and once the those substances have completely burned out, the coal starts glowing red.

(3) Natural gas can burn in a gas stove by producing a blue flame. This is because a stove has holes in its burner that allows proper amount of oxygen needed for the complete combustion of the natural gas.