A quick kitchen science activity that turns candy into a chemistry lesson!
Sometimes the most surprising science lives in your pantry. In this experiment, we watched marshmallows magically grow… then completely collapse! Kids love the “wow” moment — and it secretly teaches them about air pressure, heat energy, and molecular movement.
What We Used
- Marshmallows (any size or shape)
- Microwave-safe plate
- Microwave
- Adult supervision
What We Did
- We arranged the marshmallows on a plate (we even stacked them into a little tower!).
- We microwaved them for about 20–30 seconds.
- We watched through the window as they inflated like balloons.
- We carefully removed the plate and let them cool.
- Within seconds… they shrank, wrinkled, and turned sticky!
What We Observed
- The marshmallows puffed up HUGE inside the microwave.
- They looked soft and airy while hot.
- As they cooled, they flattened and collapsed.
- The texture changed from fluffy → gooey → chewy.
The Science Behind It
Marshmallows are actually tiny foam structures filled with thousands of microscopic air pockets.
When heated:
- The air inside warms up.
- Warm air molecules move faster.
- Faster molecules push outward.
The marshmallow expands!
When removed from heat:
- The air cools.
- Molecules slow down.
- The structure can’t hold its shape anymore.
The marshmallow collapses.
You just witnessed gas expansion and pressure changes — the same principle used in hot air balloons!
Big STEAM Concepts
Science
- States of matter
- Gas expansion
- Heat energy transfer
Engineering
- Structure vs stability
- Why materials fail when cooled
Math
- Estimate how big it will grow
- Compare before & after size
Questions to Ask Kids
- Why did the marshmallow get bigger?
- Why did it shrink afterward?
- What do you think would happen if we heated it longer?
- Would a mini marshmallow react the same as a jumbo?
Try This Next!
- Freeze a marshmallow first — does it behave differently?
- Put one in the fridge after heating — faster collapse?
- Test different shapes or brands
- Draw what it looks like before, during, and after
Safety Note
Marshmallows become extremely hot and sticky. Always let them cool before touching or tasting.
