Answer:
elastic
Step-by-step explanation:
Matter exist in three phase namely solid , liquid and gas. The molecules that make up gases are disorderly . Gaseous molecules tends to fill the whole volume of a container. Gas molecules collides randomly in the container. The individual molecule collide with each other and also collide with the wall of the container.
Generally, gases have no definite volume or shape. It will fill whatever volume that is available to it. Gases also have low density compare to liquid and solid.
Collision between gas molecules or wall of the container is elastic . This means no energy is loss during collision.