Dwayne Pointer, age 13, of  Portland, Ore., for his question:

WHAT CAUSES CONDENSATION?

Condensation in physics is the process by which matter is reduced to a more dense form, as in vapor or steam turning to liquid. Condensation comes about as a result of reducing temperature by the removal of latent heat of evaporation. The liquid product that results is known as condensate.

Removing heat shrinks the volume of the vapor and decreases the velocity of, and the distance between, molecules. According to the kinetic theory of behavior of matter, the loss of energy will lead to transforming the gas into a liquid condensate.

Condensation is an important part of distillation. It is also important to the operation of steam engines, where exhaust steam is converted back into water by a device called a condenser.

In meteorology, both the formation of clouds and the precipitation of dew, rain and snow are known as condensation.

In chemistry, condensation is a reaction involving the union of atoms in the same or different molecules.