Final answer:
Decreasing the pressure in a sealed system results in a decrease in temperature due to the direct relationship between pressure and temperature, as described by Charles's Law and Boyle's Law.
Step-by-step explanation:
When you suddenly decrease the pressure in a sealed system, the temperature of the system also decreases. This phenomenon is described by Charles's Law which states that, at constant mass, the volume of a gas is directly proportional to its temperature (in Kelvin). When the pressure is decreased, the volume tends to increase, and if the volume cannot change because the system is sealed, the temperature must decrease as a result. Similarly, Boyle's Law indicates that if the volume increases, the pressure decreases, and vice versa, at a constant temperature.
A practical example of this is when a balloon is placed in a refrigerator. The decrease in temperature results in a decrease in the internal gas volume; the balloon shrinks but if taken out and warmed up, it will expand again. In a graph of pressure versus temperature, this is shown as a direct relationship: as a gas is cooled, the pressure decreases.