Assignment Do the worksheet on vapor pressure Do

Assignment: Do the worksheet on vapor pressure. Do both sides. Side one has a chart and side two has review questions, #44 -50

Give out review books tomorrow

This was last year: Yeah yeah the sabres won with e-roth but while the cats away the mouse will play. Leggio won two. He is now 17 -4 with. 918 save % and 2. 57 Last 9 games he is 8 -1 with a 2 Gaa and. 933 save %

Some Weird Science--Phase Change & Introduction to Solutions Let’s review yesterday then the homework.

So then, what is a boiling point? The boiling point of a liquid is the temperature at which the vapor pressure is equal to the external pressure—which is usually the atmospheric pressure. What happens during boiling? The liquid has the ability to form bubbles of vapor, which then rise to the surface and release the gas. As you know, these bubbles of separated molecules form rather than the temperature rising. It is evaporation with bubbles. It is the maximum temperature at which evaporation occurs. So what makes this happen? Look again at the graph. “opposing” pressure forces!!

Why substances boil…… Notice the line here is at one atmosphere Please be careful!! This happens at different temperatures! Under normal conditions, the temperature rises until the external pressure from the atmosphere is overcome by the vapor pressure of the liquid—then the substance boils.

How did that work? This is similar to why water boils at a lower temperature on Mount Everest. You have lowered the pressure that is preventing the boiling!!

A closer look at the situation.

Animation of vapor pressure equilibrium

We have lowered the pressure, so water boils more easily. The vapor pressure necessary to boil is lower. So: New pressure line Means that: 70 A new boiling point is established What happens if the pressure above the liquid is increased?

How do you explain this? Water can be boiled using ice!!! Hyperlink for boiling water using ice Alternate website for boil water without heat. Part 2 if time

So how does the ice trick work? In the ice trick, we lowered the pressure by removing the molecules above the liquid!! So a new lower boiling point was established.

Homework review

Some cool weird extremes! Did you know that if you increase pressure you can continue to prevent boiling? Did you know there is a limit? It is called the critical temperature. Critical Temperature Pressure on Venus Vapor pressure of liquid nitrogen at the “extreme” temperature of room temperature.

Solutions and their properties Uh, like who cares—I mean why should I care? Because most chemical reactions take place in solutions! Do we remember what a solution is? A solution is a stable homogeneous mixture of substances in the same physical state. Homogeneous means that the atoms, molecules, or ions are spread out equally! Example: when you dissolve salt in water, the salt ions are uniform in the water.

In this unit you will learn to answer the following questions: 1. What is a solution and can you describe its concentration? 2. Why does salt dissolve in water but not oil? 3. Why does nail polish dissolve in acetone but not water? 4. What effects how well something can dissolve? 5. How does the amount of dissolved substance effect the freezing and boiling point?

A solution is a homogeneous mixture of substances in the same physical state. This definition can lead to some odd situations: A solid can be dissolved in a solid Gases are solutions? Liquids form solutions with other liquids? Zinc and copper form brass. Yes—like air, which does not have a definite composition Yes—certain liquids will mix with other liquids to form solutions In Regents chemistry, you will be asked to understand mostly: 1. Solids dissolved in liquid. 2. Gases dissolved in liquid.

End

Review time!! Copy this review assignment. You are to work silently at your desks, completing these questions. Go to the back of your review book and find the August ‘ 06 exam. January ’ 07 exam Do: #3, 15, 18, 43, 47 Do: 39, 66, 75, 76, 77 Note: for periods 1 and 2 you must also do the worksheet on vapor pressure. For periods 5 and 6, we will review the worksheet, then start the questions.

Hyperlink for boiling water using ice Hyperlink for soda pop that instantly freezes. Hyperlink for a seed crystal in a supersaturated solution Hyperlink for liquid nitrogen exploding a soda bottle like a rocket. Note: go back to this site to check out the magic trick—the vanishing water trick—try to find the answer!

I know I promised I wouldn’t but yesterday was “sweeps” in bowling where high score wins. First game ng— 161 second game— 214 ng third game—spare then 8 strikes in a row—had a chance for a 290, but had a 268—with handicap 292 I think I won!!

Yesterday’s assignment was: Read pg 104 -105 on boiling point. do: pg 105 # 44 -50, on the back of the worksheet.