1. Solvent, Solute, Solutions and Solubility

2. Matter Pure Substances ElementsCompoundsMixturesSolutionsSuspensions

3. Solutions All solutions consist of 2 parts – Solvent (the substance that does the dissolving, makes up the majority of the solution – usually liquid, but can also be solid or gas) – Solute (the substance that dissolves – can be solid, liquid or gas) Solution Solvent Solute A solution is formed when a solute dissolves in a solvent

4. State at RTP SolidLiquidGas SolventIronWaterNitrogen SoluteChromiumSugarOxygen, carbon dioxide and other gases SolutionStainless steel (Metal alloy) Sugar syrupAir

5. Liquid solutions at rtp – Solvent = Water? Usually, we use water as a solvent because many substances can dissolve readily in it. However, the solvent does not have to be water! Substances that do not dissolve in water may be soluble in other solvents E.g. ethanol (an alcohol), oil.. We shall focus mainly on aqueous solutions

6. Chlorine – Greenish-yellow gas – Low melting and boiling point – Poor electrical conductor Chlorine is used in bleaches for our clothes. Solvent : Solute : Water Chlorine gas

7. 7 Uses: antiseptic Iodine is a non- metallic element that sublimes when heated to form a violet vapour. When dissolved in ethanol, it forms tincture of iodine, used as an antiseptic. Solvent : Solute : Ethanol Iodine

8. Is a solution a.. Element? Compound? Mixture? Mixture! No fixed proportion of solute / solvent required

9. Solubility The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature (units: g / 100 g) Copper(II) sulfate has a solubility of 32 g /100 g in water (at 20°C)

10. Describing solutions Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C) 100 g of water (100 ml) – 2 g of copper(II) sulfate – 30 g of copper(II) sulfate – 32 g of copper(II) sulfate – 35 g of copper(II) sulfate Dilute solution Concentrated solution Saturated solution Suspension

11. Factors affecting solubility? Type of solute – e.g. copper(II) sulfate / salt / sugar Type of solvent – e.g. water / ethanol Temperature of solvent – Generally, solubility  as temperature  Pressure of surroundings – Generally, solubility  as pressure 

12. Suspension? The amount of substance present is over its solubility limit 35 g100 g Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C)

13. Suspension? The substance does not dissolve in the solvent

14. SolutionsSuspensions What happens when it is passed through filter paper? No visible change Solid particles are trapped on filter paper What happens when it is left to settle? No visible change Solid particles settle on the bottom of the beaker Is it homogenous (same throughout)? YesNo Can light pass through? Yes – solutions are ALWAYS CLEAR! No – a suspension is ALWAYS CLOUDY.

15. Common errors.. Clear solution? Transparent solution? Colourless solution! Cloudy solution? White colour solution? Milky solution? Suspension! (White precipitate in a colourless solution) X X X X X

17. Rate of dissolving

18. Rate of dissolving is NOT solubility! Recall: Rate of dissolving: How fast it dissolves The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature

19. Making solutions quickly Factors affecting rate of dissolving – Temperature of solvent – Particle size of solute – Stirring Assumption: The amount of solute used is << solubility limit