Concept:The kinetic theory of gases assumes that gas molecules are in constant motion and that energy is conserved during molecular collisions.
Explanation:Gas molecules are said to move in straight lines between collisions.
This continuous straight-line motion can only be maintained if the collisions do not reduce the molecules' kinetic energy.
If energy were lost during a collision, the molecules would gradually slow down and the straight-line motion between collisions could not continue indefinitely.
A collision in which no kinetic energy is lost is called a perfectly elastic collision.
Therefore, the statement implies that gas molecule collisions are perfectly elastic.
Inelastic collisions would contradict the postulate because they would cause a permanent loss of kinetic energy.
Forces of repulsion or attraction acting between molecules would also disturb their straight-line paths between collisions.
Answer:A. collisions are perfectly elastic.