* Deflation: The air inside the tennis ball can leak out, causing it to become softer and less bouncy.

* Compression: When a tennis ball is hit, it compresses, changing its shape temporarily. This compression is essential for the ball's bounce.

* Wear and tear: Over time, the felt covering of a tennis ball can wear down and fray, affecting its spin and aerodynamics.

* Exposure to weather: Extreme temperatures, humidity, and sunlight can all affect the ball's shape, bounce, and overall condition.

* Impact damage: A tennis ball can get cuts, scrapes, or punctures from hitting the court, fences, or other objects.

Important Note: These are all physical changes, meaning they don't alter the chemical composition of the tennis ball. If the ball undergoes a chemical change (like burning or dissolving), it wouldn't be a tennis ball anymore!