1. WATER AND SOLUTIONS

2. A solution is a mixture of a solute and a solvent.
A solvent is a substance that dissolves other materials to form a solution e.g. Water, White Spirit, nail Varnish remover.
A substance that dissolves in the solvent is called the solute e.g. coffee, salt, sugar.

3. SOLUTION solute + solvent >>>> solution
Examples of Solutions
Sugar (solute) in water (solvent)
Copper sulfate (solute) in water (solvent)
Sea water

5. Mass of solute + solvent
= Mass of solution

6. Concentrated orange solution Dilute orange solution
Bottle of
Concentrated orange solution
Glass of
Dilute orange solution

7. Concentrated solution
SOLUTIONS
A dilute solution has a small amount of solute in a large amount of solvent.
A concentrated solution has a large amount of solute in a small amount of solvent.
Dilute
solution of
copper
sulfate
Concentrated solution of
copper sulfate

8. Dilute & Concentrated Solutions
A dilute solution has a small amount of solute in a large amount of solvent.
A concentrated solution has a large amount of solute in a small amount of solvent.

9. A Solution can be made concentrated by adding more solute.
Eventually the solvent will not dissolve any more solute at that temperature. Some solute will remain un-dissolved at the bottom of the beaker
A Solution can also be made concentrated by removing some solvent - evaporation

10. Saturated Solution
Saturated Solution: A solution that contains as much dissolved solute as possible at a given temperature
The solubility of a solvent increases with temperature.

11. Solubility varies from solute to solute
The solubility of a substance is its mass (in grams) that will dissolve in 100 grams of solvent at a fixed temperature e.g.
Solubility of copper sulfate is 40g at 60°C.
Solubility varies from solute to solute

12. Solubility and Temperature
In a concentrated solution some solute will remain un-dissolved at the bottom of the beaker.
This solute can be made to dissolve by increasing the temperature of the solvent
The amount of solute that will dissolve in a solvent depends on the temperature e.g.
Coffee grains dissolve more easily in hot water than in cold water.

13. Solubility Curve for copper sulphate (solute) in water (solvent) –
The curve of the graph shows that as the temperature of the solvent increases more solute will dissolve – click to show

14. Experiment – To grow crystals of Copper Sulphate
Method;
Grind up copper sulphate using a pestle and mortar to help it dissolve more quickly
Gradually add the powdered substance to 100 cm’ of water in a beaker stirring to help the powder to dissolve. Continue adding until the solute no longer dissolves but settles at the bottom of the beaker – solution is room temperature
Heat the water to about 60 °C and note that excess copper sulphate dissolves (as seen slide).
Add more copper sulphate until no more will dissolve – solution is 600C
Pour about half of the solution into a warm evaporating basin and put it aside to cool slowly.
Cool the other half quickly by holding the beaker under running water from the tap.
Result - Crystals of Copper Sulphate are formed
Conclusion – Crystals are formed when a hot concentrated solution is cooled

15. Crystallisation
Crystallisation: The forming of crystals when a hot saturated solution is cooled. When a hot saturated solution of copper sulphate is allowed to cool, blue crystals of copper sulphate are formed.

16. END