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Nothing screams summer more than an exploding watermelon theme experiment. Also, see my 4 Week Free Watermelon Unit Study & Best Hands-on Ideas.

The exploding melon experiment is a perfect example of physics and engineering in action.

Just so you know this is one of the coolest and messiest science activity we’ve done. Be sure to do this outside for a fun summer day.

The idea is simple: you stretch rubber bands around the middle of the melon, one at a time.

Eventually, the melon explodes, shooting juice and pieces everywhere.

However, there is a lot of science to learn from this simple experiment.

KIDS BOOKS & RESOURCES ABOUT WATERMELON

First, add some of these books and fun resources.

Next, look at more fun summer themed activities.

MORE WATERMELON THEME ACTIVITIES

• How to Make a Watermelon Sensory Bin for Play and Learning
• Math Game: Roll & Cover
• How to Make Fun Watermelon Seed Slime For Summer Learning
• Seed spitting measurement
• Quilled Pendant
• Sponge Painting
  
  

Finally, look at how to do this experiment.

EXPLODING WATERMELON EXPERIMENT

You will need:

• A medium-sized watermelon
• 400-600 rubber bands
• Safety goggles

The very first step is to put on your safety goggles. 

Ensure that all observers also have their eye protection in place. This cannot be stressed enough – flying watermelon pieces can cause serious eye injury.

Choose a flat outdoor surface and set down the watermelon. 

If you are using protective sheeting, lay it down before placing the watermelon. 

Have your camera or phone ready to record the event. Consider the lighting and the angle that will best capture the explosion.

Apply the first layer, carefully placing rubber bands around the circumference of the watermelon. 

Ensure that they are distributed somewhat evenly around the widest part of the fruit.

There’s no specific pattern required, just aim for relatively uniform coverage.

Layer by layer, continue adding rubber bands, one at a time. 

As you add more, you will start to feel the tension increasing. The rubber bands will begin to bunch together and press firmly against the watermelon’s rind. 

Try to weave the new rubber bands in among the existing ones to distribute the pressure as evenly as possible. 

Using a mix of rubber band sizes can help achieve better coverage and prevent too much stress on a single point.

Once you have applied a significant number of rubber bands, pause and observe the watermelon closely. 

MELON EXPERIMENT

You may start to hear subtle cracking or popping sounds emanating from the rind.

These are indicators that the pressure is building and the watermelon’s structural integrity is being challenged. 

Be patient; the explosion won’t happen instantaneously.

Keep adding rubber bands. As the pressure intensifies, the watermelon will likely begin to deform slightly. The area around the equator will appear compressed, and the rubber bands will be tightly stretched. 

The cracking and popping sounds may become more frequent and pronounced. 

This is the exciting phase where the internal forces are nearing their limit, you can see how one end of the watermelon is bulging and catch where it was just beginning to burst.

Eventually, the cumulative pressure from the rubber bands will exceed the tensile strength of the watermelon rind. This will result in a sudden and often surprisingly powerful explosion.

The watermelon will rupture, sending chunks of rind and flesh flying outwards. Be prepared for a loud noise and a shower of watermelon debris. Maintain a safe distance during this stage.

Almost as cool as the explosion was that the rubber bands formed a tight rubber band ball when the watermelon pushed through them.

The exploding watermelon experiment  illustrates several key scientific concepts:

SCIENTIFIC CONCEPTS MELON EXPERIMENT

Energy Release: The potential energy stored in the stretched rubber bands and the compressed watermelon is suddenly released during the explosion, propelling the fragments outwards.

External Pressure: The rubber bands exert an external compressive force on the watermelon. Each rubber band contributes a small amount of tension, and the cumulative effect of hundreds of these bands creates significant pressure directed inwards towards the watermelon’s core.

Internal Pressure: Watermelons, like many fruits, have a high water content, which contributes to internal turgor pressure. This internal pressure pushes outwards against the rind, helping the fruit maintain its shape.

Tensile Strength: The watermelon rind possesses a certain amount of tensile strength, which is its ability to withstand being pulled apart or stretched. The rind can endure a certain level of external pressure before its structural integrity is compromised.

Accumulation of Force: Individually, a single rubber band exerts a relatively small force. However, by applying a large number of rubber bands, these small forces add up to create a substantial overall pressure. This demonstrates how multiple small forces can combine to overcome a greater resistance.

Material Failure: The explosion occurs when the total external pressure exerted by the rubber bands exceeds the tensile strength of the watermelon rind plus its internal pressure. At this point, the rind can no longer withstand the forces acting upon it, and it ruptures catastrophically.