1. Solutions

2. Announcements
Lab sessions this week will complete this week for your proposed labs.
8A – Both sessions Friday
8B – Wednesday and Thursday
Sugar saturation vs temp

3. Goal of the class To understand the properties of solutions
Question of the day: What causes salt to dissolve in water?
Previous Answer: Chemical equations have to be balanced on both sides because they follow the law of conservation of mass
Previous question: Why do reactions have to be balanced?

4. Solutions Solutions are mixtures at a molecular level
Molecules of solvent and solute are evenly mixed
The particles leave each other and become surrounded by the solvent
Only a certain amount of a solute may be mixed into a solution

5. Solutions and Polarity
Similarly polar molecules will dissolve in similar solvents
Example: polar molecules dissolve in polar solutions
Such as alcohol in water
Polar solvent attract the polar solute
The attraction of the solvent overcomes the attraction of the particles being mixed in

7. Solubility
It is a physical property that determines what concentration can be mixed into solution
Once that concentration has been reached, no more will mix in
The rest will separate out of solution
In the photo on the left, a solution of lead nitrate, Pb[NO3]2, is being added to a solution of potassium iodide (KI). The double displacement reaction that occurs is:
2KI(aq) + Pb(NO3)2 (aq) ⇌ 2KNO3 (aq) + PbI(s).
Potassium iodide and lead nitrate are soluble salts. That means when they are added to water, nearly all of the salt dissolves in the solvent (water), forming the clear solutions initially present in the beaker and the cylinder.
In the reaction shown, the yellow lead iodide (PbI) that is formed is insoluble; very little of any quantity of PbI dissolves in water. Instead it forms a yellow solid that falls to the bottom of the beaker—a precipitate.

8. Solubility Solubility depends on both the type of solvent and solute
It can also be affected by the temperature and pressure
Super saturated solutions can be created by heating and cooling a solution
Talk about hot tea and sugar being left in the bottom of the cup.

9. Concentration
Concentration is the amount of the solute mixed into solution compared to the solvent
A common measure of concentration is molarity (M)
Molarity equal moles/litre
Example: 24 grams of carbon in one liter is a what molar solution?

10. Dilution
The concentration of a solution can also be changed by adding more solvent
When more solvent is added, the concentration goes down
Formula: C1V1 = C2V2 (concentration, volume)

11. Practice Please think and answer the following questions:
Why does sugar form crystals when it is cooled?
What is the concentration of 10 grams NaOH in 500 ml of water?
When a reaction forms a precipitate, what do you think is the solubility of the product? Why?
Na = 23
O = 16
H = 1

12. Vocabulary
Solubility – The measure of how much solute can dissolve into a solvent at a given temperature
Saturated – Contains the maximum amount of solute under given conditions
Molarity – The number of moles per litre in a solution
Sometimes called saturation point.

13. Homework Please Read: Chemical interactions page: 92-97
Pleases complete Chemical Interactions workbook pages
impossible to solve.