【英语时差8,16】火—人类最重要的工具之一（下）

A fire needs oxygen and some kind of fuel. This fuel–whether it’s candle wax, wood, or gasoline–usually contains big molecules¹ that have carbon atoms inside them. You can think of these molecules as little containers of energy. When they’re allowed to combine with oxygen, this energy is released as heat and light. Fire is a rapid chemical reaction known as oxidation. Inside a fire, oxygen molecules break bigger molecules apart into carbon dioxide and water vapor². All the heat and light of a fire comes from big, carbon-based molecules combining with oxygen. So what is fire? It’s not the fuel or the oxygen or the heat or the light. Fire is what happens between all these things. It’s a chemical reaction.

1 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

2 vapor   

n.蒸汽，雾气

参考例句：

• The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
• This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。