Weather is the result of interactions between Earth, the atmosphere, water, and the Sun. It is about the movement of matter around the planet. Water, for example, changes phase from liquid to gas and then back to liquid as it moves from oceans to the atmosphere, to clouds, and down to Earth as rain. The atmosphere is composed of different gases, so the study of the behavior of gases is important in understanding weather. The gas laws are mathematical equations that describe the relationship between changing temperature, volume, and pressure of gases. Understanding the behavior of matter in relation to temperature allows weather experts to make predictions about the weather.