|Take four household substances: oil ,water, margarine and milk|
|This will give an example of each of the possibilities as the oil and water won't mix, the oil and margarine will and the milk and oil will mix somewhat. |
|Your students, then, can determined that oil and margarine are one type of liquid and water and perhaps milk are another.|
The oil group fit in the "H" group, which means that they have molecules that have hydrogen in them.The water group, on the other hand has an "OH" group, which means that they have a set of oxygen and hydrogen in them.
|Your students can see that soap is both a little like water and a little like oil and so soap mixes with both types of liquids|
Now have them add a teaspoon of liquid dish soap to each of the cups and mix. The oil dissolves in the oily part of soap and the watery part of soap dissolves in the water, and this is why soap works as a cleaner.