Charles's law describes the relationship of the volume and temperature of
gas at a constant mass and pressure. according to this law, what would
happen to the volume of the gas if its temperature decreased from 400 k to
300 k?

Charles's law states that the volume of a given amount of gas is directly proportional to its temperature on the kelvin scale when the pressure is held constant. with k being a proportionality constant that depends on the amount and pressure of the gas.

Explanation:

that tool would be a compass