Materials
- Shallow dish or tray
- 1 tea candle (tealight)
- Matches or lighter (adult supervision required)
- Water
- Food coloring
- Clear plastic bottle or glass (wide enough to cover the tea candle)
Instructions
- Place the tea candle upright in the center of a shallow dish.
- Pour water into the dish so it surrounds the candle but does not reach the wick.
- Add a few drops of food coloring to the water to make the movement easier to see.
- With adult supervision, light the tea candle.
- Carefully place the clear bottle upside down over the candle so the opening rests in the water and traps air inside.
- Observe the candle flame as it burns and then goes out.
- Watch how the colored water rises up into the bottle after the flame extinguishes!
What’s going on?
- As the tea candle burns, it heats the air trapped inside the bottle and uses some of the oxygen. When the flame goes out, the air inside the bottle cools. Cooler air takes up less space and creates lower air pressure inside the bottle.
- The higher air pressure outside the bottle pushes the colored water upward into the bottle. The rising water is a visible result of this pressure difference, not simply the “use up” of oxygen.
Safety
- Adult supervision is required when using fire. Keep flammable materials away and allow the bottle and candle to cool before touching.
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