1. Bell Work Describe one lab we did on Friday If not here write what you think of when you hear the word: “gas”: Homework: ch. 9 terms –Diffusion until torr Homework: pg 231 due Wednesday 12 th

2. Chapter 9 Gases Gas: comes from the Greek word: Khaos meaning formless matter Turn to page 227 in your text book –Write down 3 descriptions of gases according to the kinetic theory of gases

3. Low density Compared to solids and liquids; gases have little mass per unit of volume Compare ice at -25°C (has a volume of 0.917mL); water has a density of 0.9971g/mL( at 25°C); and steam: has a density of.000561)

4. Diffusion When a gas enters a vacuum or another gas, it spreads out to fill the entire volume with an even concentration This is due to gases physical property of being in constant motion

5. Permeability The ability of a gas to mingle with another porous substance This happens due to molecules that are always moving tend to move into the spaces between other molecules –Space invaders

6. Compression and expansibility Liquids nor solids easily compress Gases have volumes that allow them to change and fit into their containers Compressibility: When high pressures make gases squeeze into smaller volumes Expansibility: when gases encounter a region of low pressure, they quickly expand to fill the available space

7. How gases cause pressure Pressure: the average force exerted per unit area This happens when molecules collide with a boundary This fact can be observed and is a result of molecular collisions –Think of a basketball receiving too much air

8. Turn to page 229 Sample problem (dealing with atmospheres, torr, and psi) More questions –Work on pg: 254 1-3

9. Bell Work What is diffusion Turn in terms

10. Pressure, volume, and temperature A gases volume depends on: how many molecules it has, it’s temperature, and it’s pressure