What it shows
Some things disappear in water, such as salt and sugar, and some do not, such as sand and flour. We call the first group soluble.
The science
When a material dissolves, its tiny parts spread out between the water particles and we cannot see them. Salt and sugar dissolve and make clear mixtures. Sand and rice do not dissolve and settle at the bottom. Flour makes a cloudy mixture. Stirring helps things dissolve faster.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Six clear glasses (free)
- Water
- A spoon
- Salt, sugar, sand, rice, flour and turmeric, one spoon each
- Paper and pencil
- Labels
Safety
For this project: Do not drink the mixtures. An adult must supervise and keep turmeric from staining clothes.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Label the glasses with the names of the six materials.
Fill each glass half full of water.
Add one spoon of salt to the first glass and stir.
Look at the glass after one minute and write dissolved or not dissolved.
Add each of the other materials to its own glass and stir.
Wait five minutes and look again.
Sort the materials into dissolves and does not dissolve.
Draw the glasses and write the result for each.
What you should see
Salt and sugar dissolve and look clear. Sand and rice settle. Flour and turmeric make cloudy mixtures.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What does dissolve mean?
To spread out in water so you cannot see it.
2Which did not dissolve?
Sand and rice.
3How can you make sugar dissolve faster?
Stir or use warm water.
4Does the salt disappear forever?
No, it is still in the water. You can get it back by evaporating.
Take it further
Leave the salt water in a plate in the Sun and see what is left.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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