A scientist triples the temperature of a gas at constant pressure. By what factor does the gas’s volume change?

Answer 1

At constant pressure, the temperature and volume of a gas are proportional. This means that when the scientist triples the temperature of the gas, the volume of the gas will triple as well.

This is also the definition of Charles Law:  the volume of a given amount of gas is directly proportional to its temperature on the kelvin scale when the pressure is held constant.