Final answer:
According to kinetic molecular theory, individual molecules in a gas move at variable speeds, which are constantly changing due to collisions, though the average speed remains constant at a given temperature.
Step-by-step explanation:
According to the kinetic molecular theory, individual molecules in a gas move at variable speeds. This is based on the idea that each molecule behaves independently and experiences countless collisions that alter its speed. The Maxwell-Boltzmann distribution graphically represents this variability of molecular speeds, showing a range of velocities at which molecules in a gas can move at a given temperature. At any instant, there are a range of values of molecular speeds in a sample of gas, with single molecules constantly changing speeds upon collisions with others, although the average speed of all the molecules remains constant at a constant temperature.