To solve this problem, we need to understand the effects of temperature on a gas in a container.$\\$Let's analyze each option:$\\$• Option 1: Increase in its mass$\\$The mass of a gas in a closed container does not change with temperature.$\\$Mass is a measure of the amount of matter, and unless gas is added or removed,$\\$the mass remains constant.$\\$• Option 2: Increase in its kinetic energy$\\$According to the kinetic theory of gases, the average kinetic energy of gas molecules$\\$is directly proportional to the absolute temperature. As the temperature increases,$\\$the kinetic energy of the gas molecules also increases. This is the correct option.$\\$• Option 3: Decrease in its pressure$\\$For a gas in a closed container, an increase in temperature generally leads to an$\\$increase in pressure, assuming the volume is constant (as per Gay-Lussac's law).$\\$Therefore, this option is incorrect.$\\$• Option 4: Decrease in intermolecular distance$\\$As temperature increases, the kinetic energy of the molecules increases, causing them$\\$to move more vigorously and generally increasing the intermolecular distance.$\\$Thus, this option is incorrect.$\\$Therefore, the correct answer is Option 2: Increase in its kinetic energy.