Reactions fast and slow
Chemical reactions lie behind a great many of the changes going on around us. You have almost certainly met several of them today without noticing.
Some changes brought about by chemical reactions
- Iron rusting
- Fruit ripening
- Food being digested
- Yoghurt being made from milk
- Firewood burning
- A piece of zinc reacting with a dilute acid
- Sodium metal reacting with water
- Petrol vapour catching fire
- A firecracker going off
What they share, and what they do not
All nine have one thing in common: in every one of them the reactants are used up and new products appear. Every one, in other words, is a chemical change.
But there is something on which they differ sharply. A firecracker takes less than a second to go off. An iron nail takes years to rust away. Both are the same kind of change, yet the speed at which they happen is worlds apart.
The question this chapter asks
How fast does a chemical reaction go, how do we measure that, and what changes it?