If a scuba tank (a rigid, sealed gas cylinder) heats up, the correct option would be:
a. The pressure exerted by the gas in the tank would increase.
This is because, according to Gay-Lussac's Law, if the volume of a gas is held constant (as it would be in a rigid tank), the pressure of the gas is directly proportional to its temperature in Kelvin. As the temperature increases, the kinetic energy of the gas molecules increases, which results in more frequent and forceful collisions with the walls of the tank, thus increasing the pressure.
The other options are incorrect for the following reasons:
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b. The size of the gas particles in the tank would increase. Gas particles themselves do not change size with temperature. However, their kinetic energy increases, causing them to move more rapidly.
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c. The number of particles in the tank would increase. The number of gas particles is determined by the amount of gas initially in the tank and does not change simply due to an increase in temperature.
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d. The density of the gas in the tank would increase. Since the number of particles remains the same and the temperature increases (which typically leads to an increase in pressure), the density of the gas (mass/volume) does not increase; it may actually decrease if the gas expands under pressure. However, in a rigid tank, the volume doesn’t change, but density remains constant with a given amount of gas.
Thus, the most accurate answer is option a.