When air is heated, its mass remains constant. Heating air primarily affects its density and volume rather than its mass.
According to the ideal gas law, PV = nRT, where P represents pressure, V represents volume, n represents the number of moles, R is the gas constant, and T is the temperature in Kelvin. In this equation, the mass of the gas is not explicitly included.
When air is heated, its temperature increases, leading to an increase in the kinetic energy of its molecules. As a result, the average speed of the air molecules increases, causing them to collide with each other and with the container walls more frequently and with greater force.
Due to these increased collisions, the pressure of the air can increase. However, since the mass of air remains constant, the total number of air molecules also remains constant.
The volume of air, on the other hand, tends to expand when heated. This expansion occurs because the increased kinetic energy of the air molecules pushes them farther apart, increasing the average distance between molecules and thereby increasing the volume.
In summary, when air is heated, its mass remains unchanged, but its density decreases due to the expansion of the volume caused by increased molecular motion.