Some familiar mixtures
Four mixtures you have met, and what is actually in each of them. Notice how many components some of them have.
| Mixture | Components |
|---|---|
| Cement mortar | Sand, cement, water |
| Cake | Sugar, flour, water, colouring, butter |
| Well water | Water, dissolved oxygen, dissolved carbon dioxide, various salts |
| Sea water | Water, dissolved oxygen, sodium chloride, magnesium chloride, magnesium sulphate, calcium sulphate and other salts |
What the last two rows are telling you
Well water and sea water both look like one clear liquid, and both are long lists. Nothing about looking at a mixture tells you how many components it has. Sea water in particular is the mixture this chapter ends on — every salt in that row comes out of it in a different pond of a saltern.
A mixture has no fixed recipe
Two cakes can hold different amounts of sugar and both still be cake. That is the difference from a compound, where the proportion is fixed and changing it gives you a different substance entirely.
The question that comes next
Knowing what is in a mixture is one thing. How evenly it is spread through the mixture is another, and it turns out to matter a great deal — which is where the next skill begins.