Why wouldn't you expect all the molecules in a gas to have the same speed?

Answer 1

As soon as they collided, they chance their speed. All in a different way.

Th

Answer 2

See molecules in a gas follows brownian movement, so some molecules undergoes more collision as compared to another, hence, speed difference comes in. If every molecule has the same speed then either there will be no collision, or there is only molecule or the brownian movement is false, and I neither agree with the three.

Answer 3

The speed of a molecule is directly related to its temperature. Or vice versa... temperature is a measure of the average kinetic energy of atoms or molecules. So, just as the air in a room may be different temperatures in different spaces so will any container of gases.

Ther are also other factors involved like the collisions or lack of collisions between atoms or molecules where energy in the form of momentum can be transferred.

The mass of the gas atom or molecule will also make a difference. Larger mass, larger inertia, requiring more energy to make it move.

Answer 4

All other things being equal, If they were infinitely spaced and unconfined they could, but in a confined space there would be energy losses associated with collisions with each other and the walls of the container.
You measure the average speed of the molecules.