I don't know what it is, but I always seem to have candles burning a lot more frequently around Christmas time than any other time of year (which in my case means more than one time a day which is my norm). Maybe it's the whole lighting of the advent candles at church that influences me. Or maybe I'm a pyromaniac whose tenancies increase in December?? Either way, candles are very important to me and since physics is everywhere, it's definitely in candles!
Let's start with the lighting of a candle. I use matches. On the side of the match box is a strip of rough material. When you apply a force to the matchstick as you push it across this strip, the friction in between the tip of the match and the strip causes a release of energy. Due to the conservation of energy, the loss of energy in the match has to go somewhere. As you probably know, striking a match causes flame. Flames create both light and heat. That's where this energy goes. This energy is then transferred to the candle. From here, the candle experiences a phase change. The energy, in the form of heat, continues to add to the stored energy of the candle. When the energy gets high enough, the object begins to break down. So you'll notice as a candle burns longer, it starts to melt due to the addition of this form of energy.
So next time you light a candle- maybe while singing Silent Night in your church's Christmas Eve service, or maybe while writing a blog post- make sure to thank physics for making it possible.