2. What is a solution? The amount of a substance that dissolves in a given volume of solvent at a given temperature A solution in which the solvent is water What is solubility? What is an Aqueous Solution? The other substances are called solutes. What is a solute? What is a solvent? A homogenous mixture, in which the components are uniformly intermingled. The substance present in the largest amount

3. Solubility in Water : The simple rule to remember is ‘like dissolves like ++ 2-2- ++ Water is a polar solvent and will dissolve polar molecules and substances that contain charged particles. Substances that dissolve in H 2 O are said to be soluble E.g. Sugar, ethanol which are polar most ionic compounds sucrose Site of polarity can form H-bonding

4. When solid sodium chloride (NaCl) dissolves in water it breaks up into its individual ions. How is this different from dissolving sugar? Think about the experiment.

5. Water is polar, the different ends are attracted to the charged ions. 2-2-  + Cl - Na +

6. Dissolving an Ionic substance in water cationanion Surrounding water molecules

7. Substances that don’t dissolve are called insoluble E.g. Petroleum (crude oil), which are non-polar So if you want to dissolve grease which is non-polar, you need to use a non-polar solvent. Petroleum in a non-polar organic molecule

8. Remember water molecules are weakly bonded to each other by hydrogen bonds. In order for a substance to dissolve in water, the water molecules must be more attracted to the new substance added. Will this substance dissolve in water? Yes, because water will be attracted to it.

9. The substance present in the largest amount is the solvent The other substance or substances is the solute.

10. Saturated and unsaturated solutions: Even for every soluble substances there is a limit to the amount of solute that can be dissolved in a given amount of solvent When a solution can dissolve as much solute as will be dissolved at that temperature, it is said to be saturated. A solution that has not reached the limit of solute it will dissolve in it is said to be unsaturated.

11. In a saturated solution an equilibrium is reached between dissolving and recrystallization.

13. What is a concentrated solution? A solution that has a relatively small amount of solute dissolved in it. E.g. weak coffee What is a dilute solution? A solution that has a relatively large amount of solute dissolved in it. E.g. strong coffee How do you measure the composition of a solution? By mass percent and molarity (concentration)

14. 1. We can describe the concentration of a solution by using the mass percent. Mass percent is the mass of solute present in a given mass of solution. Mass Percent = mass of solute  100% Mass of solution = grams of solute  100% (grams of solute) + (grams of solvent)

15. Example 1: We make a solution by dissolving 1.0g of sodium chloride in 48g of water. What is the mass percent of the solute? Mass Percent = 1.0 g solute  100% 49 g solution = 2.0% NaCl Example 2: A solution is prepared by dissolving 1.00g of ethanol, C 2 H 5 OH, with 100.0g of water. What is the mass percent of ethanol in this solution? Mass Percent = 1.00 g ethanol  100% 101 g solution = 0.990% C 2 H 5 OH

16. Example 3: Cow’s milk typically contains 4.5% by mass of the sugar lactose, C 12 H 22 O 11. Calculate the mass of lactose present in 175 g of milk. Mass of solution (milk) = 175g Mass percent of solute (lactose) = 4.5% Mass Percent = grams of solute  100% grams of solution 4.5% = grams of solute  100% 175 g Grams of solute = (4.5%)  (175 g) = 0.045  175g 100% Grams of solute = 7.9g lactose