While the candle is still burning, place a narrow glass or flask over the candle. Carefully observe the base of the container, the water level in the container, and the flame. Record your observations. The candle will burn for a time but will eventually go out and you will see that the water rises up into the jar. You will find out that the water will rise about one-fifth of the way up the jar.
Water rises in the container due to an imbalance in pressure.
As the gas inside the container heats and expands causing bubbling around the base. The oxygen inside diminishes, the flame gets cooler, and so does the air resulting in a pressure drop. Water starts to move into the container. When the candle is extinguished, the temperature in the flask drops, causing a further reduction in pressure and a further rise in the water level. Place two sheets of notebook paper on the ruler and press against the table until the paper is flat as possible.