what causes watermelons to explode
The gas will try its best to escape the water melon but as it slowly increases due to the rotting in the water melon, the pressure will continue to increase. When the skin of the watermelon is no longer strong enough to hold the gas inside, it will explode, often spraying all nearby surfaces with rotten water melon.
Place a bunch of rubber bands around the middle of the watermelon. Be careful though as all that pressure from the outsite will start to explode the watermelon. Rubber bands are a great example of potential energy. Potential energy is energy that is stored up, not being used, just waiting to be unleashed.