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WATER AND SOLUTIONS

WATER AND SOLUTIONS. 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.

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WATER AND SOLUTIONS

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  1. WATER AND SOLUTIONS

  2. A solutionis a mixtureof 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 solutee.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

  4. Mass of solute + solvent = Mass of solution

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

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. Solubility • 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

  11. Solubility and Temperature • 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. 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

  12. 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

  13. 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 beakerstirring to help the powder to dissolve. Continue adding until the solute no longer dissolves but settles at the bottom of the beaker – solution is concentrated @ 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 concentrated @ 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

  14. 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.

  15. END

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