Dissolving and mixing — Chemistry, 4–6 years
Sometimes one material spreads through a liquid so well that it seems to disappear. The liquid and the material are still there, even though the mixture looks different.
Where did the sugar go?
When sugar is stirred into water, the sugar breaks into tiny parts and spreads through the water. It has dissolved, not vanished. The water may look clear, but it tastes sweet because the sugar is still mixed into it. A mixture is made when materials are together without becoming one new material.
Why dissolve things?
People wanted flavours, medicines and useful powders to spread evenly through water. A lump at the bottom would not reach every sip or spoonful, so mixing solved that problem. We learn about dissolving from everyday actions such as sweetening a drink, making salty water or washing with soap.
Example: sweet water
1. Pour 100 millilitres of water into a glass. 2. Add one small teaspoon of sugar. 3. Before stirring, some sugar sits at the bottom. 4. Stir ten times with a spoon. 5. The sugar is no longer visible and the water tastes sweet. It has dissolved and spread through the water.
The disappearing trap
It is natural to say that the sugar is gone when our eyes cannot see it. Stirring really does make the crystals disappear from view. But taste gives us another clue: the sugar is still in the water. If too much sugar is added, some may stay at the bottom because the water cannot dissolve it all.
Where it helps
Dissolving helps make a drink taste the same throughout, mix salt into cooking water and spread soap through water. Adults also use the idea when following instructions for powders or medicines. Only use medicines with a trusted adult; chemistry explains the mixing, not what is safe to take.
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