Title: Modification of traditional drinking candle experiment, showing water rushing into the flask when a little ethyl alcohol is rubbed inside.
Description:
In this experiment, we will modify the candle experiment by using some ethyl alcohol inside the flask, thereby reducing the pressure further
Difficulty: Easy , but need adult supervision
Materials:
1.A plate, preferably a porcelain plate
2.A small candle
3.Water, preferably water with some food coloring added
4.An Erlenmeyer flask or a similar jar to cover the candle
5.A lighter to light the candle
6.Ethyl Alcohol
Procedure:
1.Light the candle and stick it to the porcelain plate
2.Add some colored water to the plate
3.Add some ethyl alcohol to the flask and swirl it so it spreads
3.Cover the candle with the flask
4.You can see the fire momentarily jumping to the top of the flask. Also the candle will go out immediately and water will rush up to almost the top of the flask.
How It Works:
There is a chemical and physical reaction in this experiment. There are 2 chemical reactions happening here.
1. A candle is made of paraffin wax, a hydrocarbon with formula CnH2n+2. When a candle is lit, the paraffin reacts with the oxygen in the atmosphere producing water and Carbon dioxide. For n=1, the equation is
2O2 + CH4 --> CO2 + 2H2O
2.The ethyl alcohol inside the flask is set on fire by the candle. Ethyl alcohol reacts with oxygen in the atmosphere producing carbon dioxide and water per equation below
C2H5OH + O2 --> CO2 + H2O
When the candle is covered by a jar or flask, it limits the air within the flask and all the oxygen is used up in the flask by both the ethyl alcohol and the candle. As a result, the candle goes out. Both the burning candle and burning ethyl alcohol heats the air inside the flask causing it to expand. When the flame goes out, the air cools down and compresses resulting in a low pressure area within the flask. Because of the added effect of ethyl alcohol burning, the air inside the flask is very less and so more water gets sucked into the flask!.