Why Does Water Rise?

Why Does Water Rise?

A candle and some rising colored water reveal a hidden property of air that’s around you all the time.


Step 1.

Add 2-3 drops of food coloring to the water. This will make the movement of the water easier to see later. It’s interesting to watch how the drops of coloring spread through the water before stirring it.

Step 2 

Pour the colored water into the plate or dish. You want about a half-inch (1 cm) deep puddle in the plate. More is OK.

Step 3

Set the candle straight up in the puddle in the center of the plate. To make sure everything will fit, place the slender container over the candle and into the water. Make sure its base is well above the candle wick and its top edge is submerged under the water. Add water if needed.


Step 4

When the candle is stable, the water is calm, light the candle. The candle flame needs to burn brightly.


Step 5 

Turn the container over again and lower it over the burning candle. Place the container on the plate in the water and let go but don’t take your eyes off of the water level inside it. You may see bubbles coming from inside the container. At first, the candle stays burning and the water level rises slowly. About the time the candle goes out, the water rises quickly. This is the mystery: why does it rise?

Repeat the procedure several times so that you can write or draw an explanation as to why the water rises. HINT: The difference in air pressure inside and outside the container is important.


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