What happens to the core of a high-mass star after it runs out of hydrogen? a. It shrinks and heats up.
b. It shrinks and cools down.
c. Helium fusion begins right away.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.