Explanation

Rock salt is the natural mineral form of sodium chloride (NaCl).

It is commonly used for de-icing roads and in cooking as table salt.

Explanation

Reactivity is a chemical property that describes how easily a substance undergoes chemical change.

It indicates how a substance reacts with others to form new substances.

Explanation

Carbon dioxide, methane, and chlorofluorocarbons (CFS) are all significant air pollutants.

They contribute to global warming, ozone depletion, and air quality deterioration.

Explanation

Explanation

Explanation

Chlorine atoms in Chlorofluorocarbons (CFCs) are primarily responsible for the depletion of the ozone layer. 

Explanation

Melting of ice changes only the state from solid to liquid.

No new substance is formed, so it's a physical and reversible change.

Explanation

Biogas is produced under anaerobic conditions; the process is denominated as anaerobic digestion.

The major constituent of biogas is methane (55-70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia.

Explanation

Hydrogen and helium are the two lightest gases, both significantly lighter than air. 

Hydrogen: Considered the lightest gas.

Helium: Also lighter than air, but twice as heavy as hydrogen.

Air: Has a higher molecular weight than both hydrogen and helium. 

Explanation

Filtration is used to separate an insoluble solid (like sand) from a liquid (like water).

The sand stays on the filter paper, while the water passes through.