Which law states that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature?

Charles's law

The correct answer is option 3. Charles's law.

The law that states that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature is Charles's law.

Charles's law, also known as the law of volumes, states that the volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature. This means that as the temperature of the gas increases, its volume increases proportionally, and vice versa, as long as the pressure remains constant. Mathematically, it can be expressed as \(V \propto T\), where \(V\) is the volume and \(T\) is the absolute temperature.