Physics experiment: the candle that raises the water

by iw_azeheb 03 Mar

How about observing the effects of atmospheric pressure and gas expansion? The experiment of the candle that raises the water is very simple and enables us to observe these two physical phenomena. Look that:

Materials

  • A deep dish
  • A candle
  • Water
  • Dye (this item is optional, but it makes it easy to see the effect)
  • Match or lighter
  • Glass container (preferably a bottle)

The experiment

To assemble the experiment you must first glue the candle in the center of the dish and deposit the water with dye in the bottom of the dish. Then light the candle and put the glass bottle with the mouth down, leaving the candle inside the container.

What happens next is that the water begins to enter the bottle, at the same time that the flame of the candle decreases, until it is totally extinguished. When this happens, the water stops rising in the bottle..

Explanation

The most common explanation was that the burning of oxygen inside the bottle would cause the pressure to decrease, thus causing the water to rise. But the scientists gave a new explanation, because the burning of oxygen generates products (carbonic gas and water vapor) that also occupy space inside the bottle. What’s more, not all of the oxygen is burned by the flame.

The new explanation is: by placing the bottle slowly over the candle (before touching the water) the container begins to be filled with hot air and the cold air exits. When the bottle touches the water and seals the environment, the candle burns the oxygen in the container and decreases until it goes out. Simultaneously with the reduction of the flame until it goes out, the air cools and shrinks, reducing the pressure inside the bottle and the atmospheric pressure being higher causes the water to rise.

Check out the following video:

Simple and interesting, don’t you think? Now just get the materials and carry out the experiment. You can also check out other experiments that we have already told about here on the blog.

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