Final answer:
Pressure and temperature of a gas are directly proportional to each other when volume is held constant. This means if temperature increases, pressure also increases. Conversely, when temperature is constant, pressure and volume show inverse proportionality.
Step-by-step explanation:
The relationship between pressure and temperature of a gas is described by the Gas Laws. According to these laws, when the volume is held constant, the pressure of a gas is directly proportional to the temperature. This means that as temperature increases, so does the pressure and vice versa, assuming the amount of gas and the volume it occupies remain unchanged.
The exact opposite is true when temperature is held constant; pressure and volume are inversely related. Therefore, if the volume of the gas expands, the pressure decreases, and if the volume decreases, the pressure increases, when no other factors are changed.
A graph of pressure vs. temperature for a gas at constant volume illustrates this direct relationship. If a gas is cooled (temperature decreases) at constant volume, its pressure will also decrease, continuously, until the gas condenses into a liquid.
Considering Boyle's Law, which states that for a fixed amount of gas at a constant temperature, pressure decreases as volume increases (and vice versa), we can understand the inverse relationship when temperature is constant.