Step-by-step explanation:
These are some unaccounted mass that was involved. 
According to the law of conservation "matter is neither created nor destroyed but can be combined with one another". 
- The rule applies to all substances with no exception 
- When burning a candle, a phase change process is going on. 
- Some candle part of the candle occur in molten form whereas the other part is a solid. 
- In this experiment, the molten wax was not taken into consideration. 
- This accounted for the mass deficit.