Home : Patterns : Effect of Surface Area
Look at the two diagrams below
There are plenty of red molecules floating around in solution
There are the same number (25) of solid blue molecules in each diagram
For a reaction to happen a red molecule must bump into a blue molecule
The red molecule can only bump into the blue molecules on the outside of the solid
The blue molecules that are available to be bumped into are coloured in light blue
How many light blue moleculesare there in this mixture ?
How many blue molecules canreact in this mixture ?
You can see from the diagrams that the blue crystals that have been broken up into smaller pieces have more of their molecules on the outside. This means that the smaller crystals have a bigger surface area than the same amount of big crystals. The red molecules have a better chance of bumping into the smaller crystals .... This is because the smaller molecules have a bigger surface area.
Do molecules need to bump into each other for a reaction to occur ?
You can speed up the movement of molecules by giving them what sort of energy ?
You can make it more likely that they bump into each other by increasing or decreasing their concentration ?
If you grind big crystals into a powder do you make the total surface area of the crystals bigger or smaller ?
With powdered crystals are there more or less molecules on the outside of the crystal than a bigger one ?
If there are less molecules on the outside of a big crystal is it more or less likely that it will be hit by another molecule ?
The salt crystals that you use in a dishwasher are big - will they dissolve quickly or slowly ?
Icing sugar crystals are tiny - will they dissolve quickly or slowly ?
When gunpowder burns there is a very fast reaction ... are the particles big or small in gunpowder ?
Will logs of wood take a longer or shorter time to burn than the same amount of sawdust ?