Mixing and Dissolving
Candle wax will not dissolve in water.

Mixing and Dissolving

In KS2 Science children will conduct experiments involving solvents, solutes and suspensions. They will try mixing different materials and see which 'mix' (sugar dissolving in water for example) and which don't.

Mixtures are created by combining materials together. Solids, liquids, and gases can be mixed together. You will have seen some materials dissolving when you've added them to water. Sugar dissolves in water. It is a solute and water is the solvent. The mix of water and sugar is called a solution. Some other materials, like sand for example, do not dissolve in water. Instead the particles are spread out when you shake the mixture. This is called a suspension. The particles in a suspension will eventually settle to the bottom.

What's the difference between a solvent, a solute and a solution? See how much you can remember from your investigations by trying this Mixing and Dissolving quiz.

Sieving would separate which of these mixtures?
Salt and water
Sand and salt
Sand and gravel
Soil and salt
A very fine sieve would separate the coarsest sand from the salt, but it would also allow fine sand to pass through its holes
Which of these processes would you use to separate salt from the water in which it has been dissolved?
The water can evaporate but salt cannot so it will be left behind
Which of the following statements is not true?
There is no limit to the amount of a particular material that can be dissolved by a liquid
Hot liquid will be able to dissolve more of the solute
Water can dissolve more of some materials than of other materials
Different variables affect how much material a solvent can dissolve
A solution in which no more material can be dissolved is called 'saturated'
When a material is dissolved, what does it make?
A new substance or material
A gas
A force
A solution
Solids can be dissolved in liquids, creating a solution - a solution is not a new substance, however; it is a mixture of two or more materials or substances
If you mixed sand, sugar and water, which material would dissolve?
Sand and sugar
Neither sand nor sugar
Water will dissolve sugar but will not dissolve sand
What is a mixture?
A pure element
A material resulting from a chemical reaction
A chemical compound
The combination of two or more materials (substances)
The name should have given it away! Combination means joined together or mixed
Which of these would help sugar dissolve more quickly in coffee?
Using hot coffee
Using cold coffee
Using cold sugar
Not disturbing the sugar as it dissolves
Stirring, using smaller particles (by crushing, if necessary), and heating the liquid all help materials to dissolve more quickly
Which of these materials would not dissolve in water?
Icing sugar
Gelatine crystals
A candle
Sea salt
Although a candle would melt in very hot water, wax will not dissolve in water - remember that melting and dissolving are not the same process
What is a suspension?
A mixture created by combining two liquids
A mixture of two gases
A clear solution
A mixture of a solid and liquid, where the solid will not dissolve in the liquid
A good example of a suspension is a jar of muddy water - if you look closely, you can see particles suspended (floating) in the water
What is a solvent?
The material which has been dissolved in a liquid
The liquid in which a material has been dissolved
The particles remaining in suspension
The material left after evaporation
When salt is dissolved into water, the salt is a solute, the water is the solvent and the mixture is called a solution
You can find more about this topic by visiting BBC Bitesize - What is dissolving?

Author:  Sheri Smith

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