Materials
- Shallow dish or tray
- Small candle
- Matches or lighter (adult supervision required)
- Water
- Food coloring
- Clear plastic bottle (wide enough to fit over the candle)
Instructions
- Place the candle upright in the center of a shallow dish.
- Pour water into the dish so it surrounds the candle but does not cover the wick.
- Add a few drops of food coloring to the water to make the movement easier to see.
- With adult supervision, light the candle.
- Carefully place the clear plastic bottle upside down over the candle so the opening rests in the water and traps air inside.
- Observe what happens to the candle flame and the water level inside the bottle.
What’s going on?
- When the candle is lit, the flame uses oxygen inside the bottle and warms the trapped air. As the oxygen level drops and the flame goes out, the air inside the bottle cools and its pressure decreases.
- The higher air pressure outside the bottle then pushes the colored water up into the bottle. The rising water shows the pressure difference between the air inside and outside the bottle.
Safety
- Adult supervision is required when using fire. Keep flammable materials away. Allow the bottle and candle to cool before touching.
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