According to Charles's Law, when the temperature of a gas increases, its volume increases proportionally, assuming a constant pressure. This means that as air is heated, its molecules gain kinetic energy and move more rapidly, causing them to spread out and occupy a larger volume. Conversely, when air is cooled, its volume decreases. This relationship between temperature and volume is fundamental in understanding various phenomena, such as hot air balloons rising, air expansion in internal combustion engines, and weather patterns.