write Precautions, conclusion and observation
Answers
After a few seconds, you can see the flame comes down slowly and eventually goes off. You can try opening the glass when the flame is low to see how it picks up oxygen again and the flame goes higher.You can also see a small sediment of moisture in the inner walls of the glass. That is a proof that fire releases H2O.
Science Behind Candle Glass Experiment
Assume candle as a miniature version of a chemical factory. So much of chemical equations are involved in that small matter. The candle is made up of wax and the wick draws fuel called oxygen from air and burns when lighted with a matchbox. When the glass tumbler is kept on the candle the oxygen in the surrounding goes off in a while and then the candlelight also follows.
Therefore oxygen is required for the candle to burn for a long time.
Detailed science with terminologies
Hydrocarbons present in the wax are converted to carbon dioxide and steam and this chemical process is called combustion. The oxygen gets pulled at the bottom and the wick draws the fuel. This will provide heat at the top and that makes air hot to rise up. This is how a candle burns. The steam part gives the blue color to the fire. The unburned carbon deposit makes the walls nearby black. Better oxygen means brighter the flame. Match stick is required to ignite and that produces the activation energy to start the entire burning process.
The chemical equation for your reference
Methane (hydrocarbon) + Oxygen –> Carbon dioxide and Water
CH4 + 2 O2 –> CO2 + 2 H2O