Final answer:
Heating a gas sample increases its thermal energy due to an increase in the average kinetic energy of the gas particles, resulting in a higher temperature.
Step-by-step explanation:
This happens because heating the gas increases the average kinetic energy of the gas particles, which in turn means the temperature of the gas also increases. An increase in thermal energy implies that the gas particles are moving faster and therefore have more kinetic energy.
According to the kinetic theory of gases, the temperature of a gas is directly proportional to the average kinetic energy of its particles. So when heat is added (i.e., when the gas absorbs thermal energy), the average kinetic energy of the gas particles increases, leading to an increase in the system's temperature.