Launch: 2/23   Grab your binder and immediately take a seat!

  Place launch paper and yesterday’s practice questions on your desk.

  Yesterday’s Exit Slip Data:

  Today’s Objective: Exam Review!

94%!

Launch: 2/23   Grab your binder and immediately take a seat!

  Place launch paper and yesterday’s practice questions on your desk.

  Yesterday’s Exit Slip Data:

  Today’s Objective: Exam Review!

87%

Launch: 2/23   Grab your binder and immediately take a seat!

  Place launch paper and yesterday’s practice questions on your desk.

  Yesterday’s Exit Slip Data:

  Today’s Objective: Exam Review!

93%!

Launch: 2/23   Grab your binder and immediately take a seat!

  Place launch paper and yesterday’s practice questions on your desk.

  Yesterday’s Exit Slip Data:

  Today’s Objective: Exam Review!

N/A

Launch 2/23 1. What is the combined gas law?

Launch 2/23 3. Choose the right equation. At a constant temperature, a sample of CO2 gas occupies a volume of 20mL at 2 atm. What will the volume of the gas be if the pressure is increased to 20 atm?

a. 

b. 

P1 V1

= P2 V2

V1 T1

= V2 T2 P1 V1 = × P2 × V2

T1 V1 = × T2 × V2

Launch 2/23 3.  The temperature of a gas at 80mmHg is

decreased from 100K to 50K at constant volume. What is the new gas pressure?

a.  40 mmHg b.  50 mmHg

c.  500 mmHg d.  800 mmHg

Announcements   Today is a really important day!

  50 points for A-level review notes   50 points for A-level review worksheet

  Exam on Thursday!   Jeopardy tomorrow?

  For extra help, come in:   Before school (7:15am – 8:05am)   At lunch

February Calendar

Exam!

Quiz!

Today

Unit #7 Exam Review: Gases

Mr. Heffner 2/22/10

What is kinetic molecular theory?   Kinetic molecular theory states that…

  gas molecules move fast and randomly

What is diffusion?   Diffusion is…

  the process by which gases mix

random movement

Gas A Gas B

Example #1 If gas molecules are fast, why is there a

delay in smelling vinegar across a room?

What is temperature?   Temperature is…

  a measure of the kinetic energy in a substance

  °C and K

K = °C + 273

movement

Example #2 Convert 37°C to Kelvin.

K = °C + 273

K = (37) + 273

K = 310

310 K

plug & chug

temperature = collisions = pressure

What is pressure?   Pressure is…

  created by random collisions with a surface

  atm & mmHg

T & P are directly related

What is Absolute Zero & STP?

Absolute Zero   all motion stops!   Temp = 0K

  Pressure = 0 atm

STP   standard for experiments   Temp = 0°C

  Pressure = 1 atm

standard temperature & pressure

-273°C 273K 760mmHg

Example #3 Which of the following correctly show the

conditions at STP? a.  0 atm and 0°C

b.  -273°C and 1 atm c.  0K and 760mmHg d.  760mmHg and 273K

temperature = volume

What is volume?   Volume is…

  the space that an object takes up

  L & mL

T & V are directly related

What is the combined gas law?   The combined gas law is…

  There is a 3 step process for solving gas equations:

1.  Write down the combined gas law

2.  Circle given units and cross out the extras

3.  Re-write the equation, plug-in, and solve!

T1 = T2

P1 V1 × P2 × V2

At constant volume, a gas at 100K and 8 atm is cooled to 25K. What is the new gas pressure?

  Step 1: Write down the combined gas law

Example #4

T1 = T2

P1 V1 × P2 × V2

At constant volume, a gas at 100K and 8 atm is cooled to 25K. What is the new gas pressure?

  Step 2: Circle the given units and cross out the extras

Example #4

T1 = T2

P1 V1 × P2 × V2

At constant volume, a gas at 100K and 8 atm is cooled to 25K. What is the new gas pressure?

  Step 3: Re-write the equation, plug-in, and solve!.

Example #4

P1 T1

= P2 T2

8atm 100K =

P2 25K ✕

(8 atm)(25K) = (P2)(100K) 100K 100K

P2 = 2 atm

cross-multiply

Practice Questions   Review worksheet

Closing   Study Hard!

  Unit #7 Exam in 2 days!

Exit Slip 1.  How do gas molecules move?

a.  in a random pattern, colliding with other gas molecules as they move around

b.  they move in a straight line

c.  they always move from areas of low concentration to high concentration

d.  like ions found in a crystal lattice of NaCl

Exit Slip 2.  Water boils at 373K. What is that

temperature in Celsius? a.  -100K

b.  100K c.  173K d.  646K

Exit Slip 3.  Would you expect a gas at 100°C to have a

higher pressure than a gas at 0°C? a.  No, because it has less kinetic energy

b.  No, because it has a higher temperature c.  Yes, because it has more random collisions d.  Yes, because it has less kinetic energy

Exit Slip

4.  How are P & V related? a.  They are directly related. b.  An increase in volume increases pressure. c.  They change in the opposite direction

d.  They are indirectly related

Exit Slip 4.  The volume of 400mL of Ne gas at

100mmHg is decreased to 200mL at constant temperature. What is the new gas pressure?

a.  .5 mmHg

b.  200 mmHg c.  200 mL

d.  2000 mmHg

Homework   Finish practice questions