Science Experiment – Underwater candle

Science Experiment – Underwater candle

Ooh, have you heard of the underwater candle Science Experiment? Maybe yes, maybe not. You may even think of putting a candle under the water but we are doing it slightly different from that. In fact, we just require some water around the candle. Not necessarily requiring the candle to be submerged in the water.  Ok, why not we head straight to the experiment and you see how fun this can be.

What you need:
– a saucer
– some water
– an empty glass or cup
– a candle
– a lighter

Steps:
1. Stick the candle in the middle of the saucer and add some water to the saucer.
2. Light up the candle.
3. You may add some colour to the water to make it more visible.

4. Cover the candle with the glass/cup and watch what happens.

5. Water slowly starts collecting inside the glass/cup and when the flame goes off, there is a bigger gush of water going into the glass.

So, what is happening here?
When the flame is burning, the hot air expands quickly. As you cover the candle, some of the expanding air escapes from under the glass/cup. When the flame slowly fades and goes out, the air in the glass/cup cools down and the air contracts, therefore taking up less space. This contraction – low pressure – creates a very weak vacuum in the container. While the pressure outside the glass is high, it pushes the water into the glass/cup until the pressure is equalized both inside and outside.

Now you know what is happening? Isn’t this fun and interesting? Go ahead and try out with different types of candles and/or different sizes of the glasses/cups and observe what happens. Have fun!

Catch our video here while smarties were having fun with the experiment.

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