Which candle will be extinguish first? | English
Channel: IISER Pune Science Activity Centre
Date: 2018-09-27

Three candles of different heights are extinguished by putting a glass over them. Which one will extinguish first? What is the reason if one of them goes off first? Let’s find out by actually performing this experiment and learn the science behind it!


When you try to extinguish a candle by putting a glass above it, does all the oxygen get consumed? Or there is any other reason why the candle goes off? What will happen if you had three candles of different heights? Which one will go off first? Or all of them will go off simultaneously?
All this questions can be answered by a really simple experiment. Three candles of different heights are lit. Put an inverted glass over them to extinguish them. You’ll notice that he tallest candle extinguishes first followed by the middle one and the shortest one is the last to go off. Why did this happen?
Burning produces carbon dioxide which is heavier than other gases in air. This suggests that the lowest one should get extinguished first. But as the carbon dioxide is being produced, it is also heated up due to the flame. This hot gas expands and has lower density this accumulates at the top of the glass. Thus the top candle experiences deficit of oxygen first followed by the middle one and finally the last one.
This happens due to the combination of expansion of hot gases and oxygen deprivation which results in extinguished candles. This experiment allows students to think about multiple factors that may play a role in certain experiment and how to account for them while interpreting results.
Hope you learned something new today and understood the process pf convection currents. For more exciting experiments about math’s and science subscribe to or YouTube channel.
Thanks!

Team: Ashok Rupner, Chaitanya Mungi, Neha Apte, Sajeda Sayyad_Shaikh, Pinki Saha, Students of NCL School Pune, Dr. B N Das