* Kinetic Energy: The speed of a particle is related to its kinetic energy, which is the energy of motion. The equation for kinetic energy is:

KE = 1/2 * mv²

where:

* KE is kinetic energy

* m is mass

* v is velocity (speed)

* Equal Kinetic Energy: If two particles have the same kinetic energy, the heavier particle will have a lower speed than the lighter particle. This is because the heavier particle needs to move slower to have the same amount of kinetic energy.

* Temperature: In a system of particles, like a gas, the average kinetic energy of the particles is directly proportional to the temperature. Therefore, at a given temperature, all particles will have the same average kinetic energy, regardless of their mass. This means heavier particles will move slower than lighter particles.

Example: Imagine a bowling ball and a ping pong ball. If they both have the same kinetic energy, the bowling ball will move much slower than the ping pong ball.

Important Note: This explanation assumes that the particles are at the same temperature. If the particles are at different temperatures, the heavier particles will have a higher kinetic energy at a higher temperature, and therefore a faster speed.