GEOLOGY

Detailed explanation-1: -Convection is a process in which hot, less dense materials rise upward and are replaced by colder, more dense materials.

Detailed explanation-2: -When a liquid or gas is heated, the molecules move faster, bump into each other, and spread apart. Because the molecules are spread apart, they take up more space. They are less dense.

Detailed explanation-3: -Warm air rises primarily due its lower density as compared to cooler air. As the temperature increases, the density of the air decreases. But even air that is of a lower density will not begin to rise by itself.

Detailed explanation-4: -So air, like most other substances, expands when heated and contracts when cooled. Because there is more space between the molecules, the air is less dense than the surrounding matter and the hot air floats upward. This is the concept used in the hot air balloons.

Detailed explanation-5: -Because there’s more space between the molecules, a volume of hot water has fewer molecules in it and weighs a little bit less than the same volume of cold water. So hot water is less dense than cold water.