Do atoms or molecules of different compound have different speed (kinetic energy) when the temperature is the same?

If they have the same mass?

Yeah, there will be a range.

Yes, there will be a range, but for the same mass, the average speed will be the same. Temperature is related directly to kinetic energy.

What's that it mean?

think of simple water, when it`s ice, it`s molecules are stationary, then add some heat (energy) to it, and it becomes water and free to move. Add some more heat (Energy) to is and it becomes Steam, and VERY free to move, the H2O is vibrating like crazy at that point with enough "speed" to cause a burn as it`s molecules transfere their vibrational speed to your skin, like zillions of tiny collisions (friction).

 

the common factor here is: Energy = Speed/vibration (in molecules)

 

this is only a simplified answer/ expansion on Swansont`s post, and does not take into account the ranges

Read this

I believe that the question was not talking about the speed difference of different atoms within one substance, but instead its asking if there is a difference between the speeds of atoms within two different substances. For instance, lets consider three different beakers: one contains air, one contains water, and one is filled with salt. If we just looked at the beaker filled with water molecules we would find that the molecules of H2O within the beaker were moving at different speeds. Water molecule one is moving at 1mile per hour, molecule 2 is moving at 2 miles per hour, and molecule 3 is moving at 3 miles per hour(completely unrealistic speeds). The average speed of the beaker is 2 miles per hour and every other beaker of water at the same temperature and pressure has the same average speed of H2O molecules. However if you compared the average speed of the water molecules to the solid salt molecules you would find them moving slower at an average of 1 mile per hour and the beaker's average molecule speed would be higher at 3 miles per hour.

 

Larger molecules move more slowly at the same temperature. This is because to contain the same amount of energy they have to move more slowly. Molecules of different states move at different speeds: gas>liquid>solid

 

The molecules of the air im breathing now are moving more quickly than the atoms of the chair im sitting in and the molecules of O2 that im inhaling are moving faster than the CO2 that im exhaling.

there`s no one in disageement with that though