What happens to pressure if temperature is doubled and why does increasing the temperature of the gas cause the volume to increase?
In a first order approximation, one can often consider gases as perfect (cf. https://en.wikipedia.org/wiki/Perfect_gas). In such framework, the product of pressure by volume divided by the absolute temperatire is constant. So if temperature is doubled, pressure can be anything as a function of volume. If volume is constant, pressure will double. This answer leaves obviously aside many aspects including but not limited to Equation Of State beyond perfect gas law, chemistry, .... A lead to dig into the why would be to look for Boltzmann approach to the perfect gas model.
If you heat a gas you give the molecules more energy so they move faster. This means more impacts on the walls of the container and an increase in the pressure. Conversely if you cool the molecules down they will slow and the pressure will be decreased. Hence, if temperature is doubled the pressure will also be doubled. The two quantities are directly proportional to one another. The ratio of Pressure/ Temperature remains constant. As such, a doubling of the Kelvin temperature wills double the pressure of the gas. As you can see, air pressure does vary according to temperature. Cold air is denser than warm air, i.e., it weighs more. As a result, it tends to sink. Warm air, on the other hand, is less dense. As the temperature increases, the average kinetic energy increases as does the velocity of the gas particles hitting the walls of the container. The force exerted by the particles per unit of area on the container is the pressure, so as the temperature increases the pressure must also increase. As the temperature increases, the kinetic energy of the gas molecules increases, and their velocity also increases. Also, their intermolecular forces weaken, resulting in the expansion of spaces between the molecules, which in turn leads to an increase in the volume. In simple terms, at constant pressure, the volume of a fixed mass of gas is directly proportional to temperature. It can be stated as: “The volume of a fixed mass of a gas decreases on cooling it and increases by increasing the temperature. As temperature of gas molecules increase, they become more energetic, so they move a lot faster and spread out a lot more to occupy more space. The volume of a sample of gas is dependent upon the Kelvin temperature of the gas. Increasing the Kelvin temperature increases the volume. The two quantities are directly proportional to one another. A doubling of the Kelvin temperature wills double the volume of the gas.
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