1. Gases, non polar solvents and “like dissolves like”.
In this lesson we will answer such questions as:
Why won’t salt dissolve in oil?
Why won’t paint thinner mix with water?
Why do non polar substances dissolve in non polar solvents but not polar solvents?
So how do soaps make grease dissolve in water?
Continuing most likely move on with effects of temp and pressure on gases and like dissolve like and saturated supersaturated etc.

2. Goals today:
Learn how non polar solvent and solutes work. You can show me you know by answering some sample questions.
Understand how gases dissolve-like in soda pop. You will also know why warm pop “fizzes up” so easily. Again yu will answer some questions.
3. Understand a concept called heat pollution.
4. Finally, you will return to table G to learn how to handle some final tricky questions.

3. Copy tonight’s assignment please.
Read pages in the text and learn something!!

4. Yesterday’s Assignment:
Regents questions in review book.
read pages
Do page 120: 1-8, 10
page 132: 1-5

5. What determines the solubility of a substance?
We must consider the affect of:
Temperature, pressure, and the solvent---on the solutes we are attempting to dissolve, mainly solids and gases. (next 2 days)
There are two general kinds of solvents:
1. Polar—solvents with dipole molecules like water.
2. Nonpolar—solvents with weak dipoles like benzene and acetone.
There are two kinds of solutes:
1. Polar—ionic substances, and polar molecules.
2. Nonpolar—usually weak dipoles in organic substances. Examples include oils, waxes, Br2, CO2, N2
copy
copy

6. Why do non polar solids dissolve in non polar liquids?
Ok so how does dissolving work for non polar substances?
Let’s take a look at the theory.
We will go over the whole page.
Let’s see this operate with real solutes and solvents.
This can be summarized in a phrase— “like dissolves like”. What this refers to is whether a solute and solvent are polar or non polar. Like is short for “alike”. So non polar solvents dissolve non polar solutes, and polar solvents…..
Why do non polar solids dissolve in non polar liquids?
Answer: the solute-solute bonds and the solvent solvent bonds are all weak, so random motion produces a spread out average mixture.

7. Can you answer the following questions now?
1. Why won’t salt dissolve in oil?
the oil is non polar and can’t grab the polar solute to dissolve it
2. Why won’t paint thinner mix with water?
water molecules are not attracted to paint thinner so it stays bonded to itself.
3. Why won’t non polar solutes dissolve in water?
water molecules aren’t attracted to non polar solutes, so water stays bonded to itself.

8. Now what happens when: ethanol mixes with water? oil and gasoline mix?
Answers: if you mix two liquids and they are both polar, or if you mix two liquids that are non polar, they will mix and are said to be miscible.

9. So, we have covered solids in liquids, and liquids in liquids, now let’s look at gases in liquids.
Let’s look at how temperature and pressure effect the solubility of gases.
Summary of solubility of gases:
Effect of pressure: as pressure rises the amount of gas dissolved rises—you literally push the gas into the liquid. Gases overall are not very soluble, but you wouldn’t think so drinking pop!
Effect of temperature: it is the opposite of pressure. As temperature rises the amount of dissolved gas decreases. Faster molecules escape more easily.
The most common consequence of this is heat pollution.

10. End

11. Answer these questions from the Table: Find KCl at 50°C.
Now, let’s look at what Table G means in terms of the limit of solubility.
Answer these questions from the Table: Find KCl at 50°C.
In 100 ml of water how much KCl can dissolve?
(answer: 42 grams)
2. What would happen if more KCl were added?
(answer: it would not dissolve, but would fall to the bottom)
What if only 20 grams of KCl had been dissolved—how much more KCl could be added?
(answer: another 22 grams)

12. To cover these situations, we have a couple of terms:
When a solution can still dissolve more solute at a given temperature it is said to be unsaturated.
When no more solute can dissolve, the solution is said to be saturated.
This shows what happens with polar and non polar substances—solutes and solvents.

13. Here are some of the concepts you are expected to know form the regents syllabus. We will tackle these in the next couple of days.