A substance X is added to LPG cylinders while filling so as to make the detection of leakage of LPG from the cylinders easy.

(a) Name the substance X

(b) How does substance X make the detection of leakage of LPG easy?

Fossil fuels are energy rich compounds of an element X which were originally made by the plants with the help of sun’s energy.

(a) Name the element X

(b) Name another element which is usually found in combination with X in fossil fuels.

The energy in petrol originally came from the Sun. Explain how it got into petrol.

The pollution of air caused by burning petroleum fuels (like petrol and diesel) in vehicles can be controlled by fitting a device X in the exhaust system of vehicles.

(a) Name the device X

(b) How does this device help in controlling air pollution ?

A hydro-power plant converts one from of energy into another. Name the two forms of energy.