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The particles which of the following gases has the highest/lowest average speed? Which gas particles have the highest/lowest average kinetic energy? a.) argon at 20°C. b.)nitrogen at 20°C b.) nitrogen at 100°C. c.) helium at 100°C

1 Answer
Mar 11, 2018


Highest speed: Helium at #100°C#.
Lowest speed: Argon at #20°C#.

Highest kinetic energy: Nitrogen and helium at #100°C#.
Lowest kinetic energy: Nitrogen and argon at #20°C#.


Temperature is a measure of average kinetic energy.

Therefore, at the same temperature, gases have the same average kinetic energy.
But different gas particles move at different speeds with this kinetic energy—gases with smaller particles tend to be moving faster at the same temperature, which means they have a higher speed.

At variable temperatures, gases with both smaller particles and higher temperatures will have a higher speed.

Here are our choices:

  1. Argon at #20°C#.
  2. Nitrogen at #20°C#.
  3. Nitrogen at #100°C#.
  4. Helium at #100°C#.

Helium has both the smallest particles and is at the high temperature of #100°C# , so it will be the gas with the highest speed.
Argon has the biggest particles and is at the low temperature of #20°C#, so it will be the gas with the highest speed.

Particles at the same temperature have the same average kinetic energy, so argon and nitrogen, which are at #20°C#, are the gases with the lowest average kinetic energy.
Nitrogen and helium, at #100°C#, have the highest average kinetic energy because they have the highest temperature.