Final answer:
When the volume of an ideal gas is doubled at constant pressure, following Charles's law, the temperature also doubles to maintain the volume-temperature ratio.
Step-by-step explanation:
If the volume of an ideal gas is doubled at constant pressure, the change in the temperature of the gas can be found using Charles's law. According to Charles's law (V1/T1 = V2/T2), at constant pressure, the volume of a gas is directly proportional to its temperature in kelvins. Thus, when the volume is doubled (V2 = 2V1), the temperature also doubles to maintain the ratio, meaning T2 = 2T1.
Therefore, the correct answer to what happens to the temperature when the volume is doubled at constant pressure is that the temperature will be doubled. This can be represented mathematically as T'=2T, where T' is the new temperature.