Evidence for Molecules
When a lump of sugar dissolves in water, it disappears and all you can see is a clear liquid. It seems as if the sugar has disappeared. Yet, if you drink the liquid, you can taste the sugar. Therefore the sugar is in the liquid somewhere. Why can’t you see it?
The question is easily answered. Think of sugar as being made of millions of molecules all packed closely together. Water is also made up of millions of molecules but they are not packed so closely together. They move around quite freely.
When sugar dissolves in water, the sugar molecules move into the spaces between the water molecules. Remember that the water molecules are not packed closely together. The sugar and water molecules mix together and make a solution.
Answer these questions based on the text.
1. What will happen if a lump of sugar dissolves in water?
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2. Do you think it really disappears? Why?
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3. Which one are closer packed, molecules of water or sugar? How do you know?
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4. Where are the molecules of sugar when it dissolves in water?
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5. What thing is made when the sugar and water molecules mix together?
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