Today’s Wonder of the Day was inspired by Er. Er Wonders, “Does wood melt? Is there liquid wood?” Thanks for WONDERing with us, Er!
How much do you love electricity? It powers your favorite electronic devices. It can cool you in the summer and warm you up in the winter. It lights your way after the Sun goes down.
When a thunderstorm brings lightning and thunder, however, you might lose electricity if important electrical components, such as transformers, get hit by lightning. What do you do then?
You could sit in the dark and wait for the lights to come back on, but that's a bit boring. Instead, you probably grab a flashlight so you can keep reading your favorite book. Can you imagine what it was like for kids long ago before electricity? What would it have been like to read by candlelight every evening?
If you've ever watched a candle burn, you may have noticed something interesting. The candle wick that you light burns. But what about the rest of the candle? The wax melts. So why do some things burn while others melt?
Although it might seem like burning and melting are two sides of the same coin, they're actually different processes. Different materials react differently when exposed to heat.
Melting is a physical process that involves the phase transition of a substance from its solid to its liquid state. Burning, on the other hand, is a chemical process that involves a substance being broken down and changed into different substances.
For example, when an ice cube melts, it changes from a solid cube of ice into liquid water. It's still the same substance, though: water. When wood burns, though, it changes from its original composition (cellulose, lignin, water, etc.) into new substances (charcoal, methanol, carbon dioxide, etc.).
Substances that burn instead of melt have combustion temperatures that are lower than their melting points. Before they have a chance to be heated to a temperature high enough to melt, they react with oxygen in the atmosphere and combust or burn.
This is the case with wood. You've probably noticed that wood exposed to heat doesn't melt. Instead, wood reacts with oxygen in the air and burns, turning into charcoal, ash, and other substances in the process.
If you've ever tried to take charcoal, ash, and the other remnants left over from a campfire and turn them back into wood, you know it's not possible. That's because a chemical change has taken place. If you have liquid water, though, you can cool it to its freezing point to make it complete a phase transition back into a solid.