StraighterLine Physics Practice Test

As temperature rises, the density of a gas typically decreases. This occurs because gases expand when they are heated. According to the ideal gas law, which is represented by the equation PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the universal gas constant, and T is temperature, an increase in temperature (T) while keeping the number of moles and pressure constant leads to an increase in volume (V). Since density is defined as mass per unit volume, if the volume increases while the mass of the gas remains constant, the density must decrease.

This phenomenon is particularly evident in everyday life: for example, warm air is less dense than cold air, which is why hot air balloons rise. The warmer air inside the balloon expands, decreases in density, and allows the balloon to lift off the ground.