1. The problem statement, all variables and given/known data If we initially lighted a candle, and then put a jar over it, what can we say about the fire? What kind of observations can we make? How can you verify your claim? 3. The attempt at a solution Well the observations are quite obvious. The flame is put off soon or later. I want to know is it true that there is as much CO2 produced as O2 used? If the initial state has 10 C, and 10 O2 molecules, we can make 10 CO2. The mass + energy is conserved, also. What kind of scientific sensor / tool can detect and find out the composition of air (quantitatively) ? I haven't done chemistry for a few years so I am sorry for the abrupt question here. Thanks!