Leah all set to get dissolving

Activity: Dissolving Sugar

On SCOPE's Medicines episode, you saw Leah find out about solubility by using sugar. Here's how she did it:

Watch this clip.

What you need

• 3 types of sugar (raw, brown and coffee)
• 3 glasses
• 3 spoons

What to do

1. Fill the three glasses with equal quantities of cold water.
2. Place the different sugars each behind a glass.
3. Add one spoonful of brown sugar to the first glass, raw sugar to the middle glass and coffee sugar to the final glass.
4. Stir each glass 20 times.
5. When everything has settled it is time to look at the results.

What's happening?

Anyone who has sugar in their tea or coffee knows that it dissolves, but, not all sugars dissolve the same way. In our experiment the brown sugar completely dissolved, the raw sugar mostly dissolved and the coffee crystals had only dissolved a small amount.

The reason for this is surface area. The more surface area the sugar crystals have the quicker they will dissolve. The brown sugar is made up of very fine particles. They have a large surface area and will be surrounded by water and dissolved quicker than the mid-sized crystals of raw sugar and the large coffee crystals.

It is important in this experiment that the only variable (or thing we change) is the type of sugar being tested. This means all the other factors (amount and temperature of water, amount of sugar, amount of stirring etc) must be kept the same as far as possible.