You can tell this reaction is unbalanced because there are four carbon atoms on the left side and only one carbon atom on the right. There are 10 hydrogen atoms on the left side and only two on the right. As you can see, there will be no butane left after the reaction is completed. Although the fuel is consumed, the atoms that made up the fuel still exist as parts of other molecules. At some point you have seen the element magnesium burning.
Magnesium burns with a blinding white light.
A white powder called magnesium oxide. Suppose you took a piece of magnesium, put it in a ceramic crucible, and massed it on a balance and found that the total mass was 25.210 g. Then you lit the magnesium on fire, watched it burn until it stopped, and then massed it again. The second mass would be higher than the first mass. The second time you massed the compound magnesium oxide, which has a greater unit mass then the magnesium alone.