Particles

Particles can be thought of as tiny little balls of "stuff". If you use this model, you have to be sure to understand just how small these particles are.

There are a few ways to picture this:

A thimble full of water probably contains 100000000000000000000000 water particles.

This is a huge number! Imagine a model of Britain in which every model person also had a model of Britain and each of these tiny model people also had a model of Britain with the right number of little people. If you count up all the little people from all of these models you are still less than the number of water particles we quoted.

Or imagine you were there at the start of the Earth's history and decided to count up from one at the speed of one number per second. You would still not be at our particle number today, 4.5 billion years later.

Or imagine taking a cup full of water from the sea. If you were somehow able to label "your" water particles and then put them back into the sea and stir up all the seas and oceans, the next cup full of water would contain around ten of your original particles. This shows that there are ten time more molecules in a cup of water than there are cupfulls in all the seas and oceans.