The process of transformation of a substance in a gaseous state into a liquid state due to change in pressure or temperature of the substance is called:

condensation

The correct answer is option 2. condensation.

Condensation is the process by which a substance in its gaseous state transforms into its liquid state. This transformation occurs when the temperature or pressure of the gaseous substance decreases to the point where the molecules lose enough kinetic energy to come together and form liquid droplets.

Here's a more detailed explanation:

1. Temperature Decrease: When the temperature of a gas decreases, its molecules lose kinetic energy. As a result, they move more slowly and have less energy to overcome the intermolecular forces of attraction between them.

2. Pressure Increase: Alternatively, condensation can occur when the pressure on the gas increases. This can happen, for example, when a gas is compressed. Increasing pressure on a gas reduces the space between its molecules, making it easier for them to come together and form liquid droplets.

3. Formation of Liquid Droplets: As the temperature decreases or pressure increases, the gas molecules come closer together and begin to cluster. Eventually, they reach a point where they are close enough to form liquid droplets. These liquid droplets then coalesce and collect on surfaces, resulting in condensation.

4. Examples: Condensation commonly occurs in various natural phenomena, such as the formation of dew on grass in the early morning, the formation of clouds in the atmosphere, or the mist that forms on a cold surface when warm, humid air comes into contact with it.

In summary, condensation is the reverse process of evaporation. While evaporation involves the transformation of a liquid into a gas, condensation involves the transformation of a gas into a liquid. It occurs when the temperature decreases or pressure increases, causing gas molecules to come together and form liquid droplets.