Final answer:
The decrease in temperature from 22℃ to -21℃ leads to a decrease in the average kinetic energy of the gas particles in the weather balloon, causing them to move more slowly.
Step-by-step explanation:
The change in temperature from 22℃ to -21℃ will affect the gas-particle motion inside the weather balloon. According to the kinetic molecular theory, the temperature of a gas is related to the average kinetic energy of the particles. When the temperature decreases, the kinetic energy of the gas particles also decreases, which causes the particles to move slower.
The decrease in particle movement inside the balloon at the higher altitude where it is colder would, under constant pressure, lead to a decrease in volume according to Charles's Law. However, depending on the conditions, the balloon may not shrink because the external pressure also decreases with altitude and may compensate for the internal pressure drop. But the specific question regarding the effect on gas-particle motion would result in slower moving particles at the decreased temperature.