Today’s experiment is very simple but hopefully fascinating for even very young children. We’re going to investigate which solids dissolve in water.
When a substance dissolves in water, you can’t see it anymore; it’s still there but has mixed with the water to make a transparent liquid called a solution.
We call substances that dissolve in water soluble. Sugar and salt are examples of soluble substances.
Substances that do not dissolve in water are called insoluble. Sand and flour are examples of insoluble substances.
- Transparent containers – test tubes or beakers
- Water ( warm and cold )
- Substances to try to dissolve, e.g. sugar, coffee, pepper, sand, flour, salt.
Add a teaspoon of whichever solid you are testing to a glass of cold water and a glass of warm water. Stir and observe the difference.
Watch to see if the solid dissolves in warm and cold water and if one is better than the other.
Remember to use the same amount of each solid and the same amount of cold and warm water to make the investigation a fair test.
Can you design a chart for recording your observations?
Which solids dissolve in water
Things like salt, sugar and coffee dissolve in water. They are soluble. They usually dissolve faster and better in warm or hot water.
Pepper and sand are insoluble; they will not dissolve even in hot water.
Dissolving for older children
Everything is made of particles which are constantly moving. When a soluble solid ( solute ) is mixed with a suitable liquid (solvent), it forms a solution. This process is called dissolving.
Two things that affect the speed at which a solid dissolves are temperature and the size of the grains of the solid.
Caster sugar, made of fine particles, will dissolve quickly, but bigger sugar particles will take longer.
Solids dissolve faster in hot water; in hot water, molecules move more quickly, so they bump into each other more often, increasing the rate of reaction.
An example of a physical change
Dissolving is an example of a physical change. The particles involved are rearranged, but no chemical bonds are changed.
In a physical change, there is no change in mass. If you dissolved 10g of salt in 100g of water, you’d have 110g of solution.
More Dissolving Experiments
Make a naked egg and watch as vinegar dissolves the calcium carbonate of the eggshell.
Lava lamps work because the effervescent tablet dissolves in water releasing carbon dioxide.
Solute – the solid being dissolved
Solvent – the liquid the solid is dissolving into.
Solution – the solute and the solvent
Soluble – solute that does dissolve
Solubility – how much of a solute will dissolve
Insoluble – does not dissolve
Saturated – a solution that won’t dissolve any more solute at that temperature.
More Science for Kids
Don’t forget we have lots more easy science experiments for kids at home you can try too!
You might also like our science books! This IS Rocket Science contains 70 fun space experiments for kids, including bottle rockets, film canister rockets, space marble runs and shadow puppets.
Snackable Science contains 60 tasty and edible science snacks!!
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Last Updated on January 24, 2023 by Emma Vanstone