Rubber bounces because it is an elastic material. Elasticity is the ability of a material to return to its original shape after being stretched or compressed. When a rubber ball hits the ground, it is compressed. The rubber molecules in the ball are stretched and then they quickly return to their original shape. When this happens, the ball bounces back into the air.

The amount of bounce that a rubber ball has depends on a few factors, including the type of rubber, the thickness of the ball, and the temperature. Rubber balls made from natural rubber tend to bounce higher than rubber balls made from synthetic rubber. Thicker balls also tend to bounce higher than thinner balls. And balls that are warmer tend to bounce higher than balls that are colder.

Here is a more detailed explanation of the physics behind why rubber bounces:

When a rubber ball hits the ground, the force of the impact causes the rubber molecules in the ball to stretch. The rubber molecules are held together by chemical bonds, and when these bonds are stretched, they store energy. When the rubber molecules return to their original shape, they release this energy as kinetic energy, which is the energy of motion. This kinetic energy causes the ball to bounce back into the air.

The amount of energy that is stored in the rubber molecules depends on the force of the impact. The harder the ball hits the ground, the more energy is stored in the rubber molecules. And the more energy that is stored in the rubber molecules, the higher the ball will bounce.

The elasticity of rubber also affects how high a ball bounces. Elasticity is a measure of how well a material can return to its original shape after being stretched or compressed. Rubber is a very elastic material, which means that it can return to its original shape very well. This is why rubber balls bounce so high.

The thickness of the ball also affects how high it will bounce. Thicker balls have more rubber molecules, which means that they can store more energy. This is why thicker balls tend to bounce higher than thinner balls.

Finally, the temperature of the ball also affects how high it will bounce. Rubber becomes more elastic as it gets warmer. This is why rubber balls bounce higher when they are warm than when they are cold.