Launch: 2/10 Grab your binder and immediately take a seat!
Place launch paper on your desk.
Yesterday’s Benchmark Data:
Today’s Objectives: I can apply the gas laws to relations between temperature and pressure.
96%!
Launch 2/10 1. What is the equation for converting
between the Celcius and Kelvin scales? Label the variables.
Launch 2/10 2. Molecules in a substance at 50°C
a. move slower than molecules in a substance at 25°C because they have less kinetic energy
b. move slower than molecules in a substance at 25°C because they have more kinetic energy
c. move faster than molecules in a substance at 25°C because they have less kinetic energy
d. move faster than molecules in a substance at 25°C because they have more kinetic energy
Launch 2/10 3. What is the equivalent of 423K in degrees
Celsius? a. -223°C
b. -23°C c. 150°C d. 696°C
Launch 2/10 4. Convert -50°C to Kelvin.
a. -223 K b. -50 K c. 223 K d. 323 K
Announcements Great job yesterday!
No quiz on Friday
Class points end on Friday
Only 3 days until break… Let’s finish strong
February Calendar
Exam!
No quiz!
Quiz!
Today
Opening Today’s Objective: I can apply the gas laws to
relations between temperature and pressure. Standard – CH.4.c
Today’s Questions: How are P and T related?
How are P & T related? Mr. Heffner 2/10/10
How are P & T related? Temperature is…
a measure of movement
°C & K
Pressure is… a measure of random collisions
atm & mmHg
How are P & T related?
temperature = collisions = pressure
temperature = pressure
How are P & T related? Pressure & Temperature are…
directly related
In math terms…
change in the same direction
P T = constant
“some number”
How are P & T related? By rearranging the relationship, we can get an equation
P1 T1
= constant = P2 T2
starting conditions
ending conditions
P1 T1
= P2 T2
How are P & T related? There is a 3 step process for solving gas equations:
1. Write down the equation and given conditions
2. Plug in for the variables
3. Solve for the unknown
At 298K (room temp), the pressure inside an empty Coke can is 1 atm. It is then thrown into a bucket of ice at 273K. What is the new gas pressure?
Step 1: Write down the equation and given conditions
Example #1
P1 T1
= P2 T2
P1 T1 P2 T2
= =
= =
1 atm
298K
273K ?
At 298K (room temp), the pressure inside an empty Coke can is 1 atm. It is then thrown into a bucket of ice at 273K. What is the new gas pressure?
Step 2: Plug in for the variables
Example #1
P1 T1
= P2 T2
P1 T1 P2 T2
= =
= =
1 atm
298K
273K ?
1 atm 298K =
P2 T2
1 atm 298K =
P2 273K
At 298K (room temp), the pressure inside an empty Coke can is 1 atm. It is then thrown into a bucket of ice at 273K. What is the new gas pressure?
Step 3: Solve for the unknown
Example #1
1 atm 298K =
P2 273K
✕
(1 atm)(273K) = (P2)(298K) 298K 298K
P2 = .92 atm
cross-multiply
The pressure of oxygen gas at 300K is reduced to from 760mmHg to 380mmHg. What is the final temperature?
Step 1: Write down the equation and given conditions
Example #2
P1 T1
= P2 T2
P1 T1 P2 T2
= =
= =
760 mmHg
300K
? 380 mmHg
The pressure of oxygen gas at 300K is reduced to from 760mmHg to 380mmHg. What is the final temperature?
Step 2: Plug in for the variables
Example #2
P1 T1
= P2 T2
P1 T1 P2 T2
= =
= =
760 mmHg
300K
? 380mmHg
760mmHg 300K = 380mmHg
? 760mmHg
300K = P2 T2
The pressure of oxygen gas at 300K is reduced to from 760mmHg to 380mmHg. What is the final temperature?
Step 3: Solve for the unknown
Example #2
✕ (760mmHg)(T2) = (380mmHg)(300K)
760mmHg 760mmHg 150K = T2
760mmHg 300K = 380mmHg
T2 1
2
The pressure of Cl2 gas is 1 atm at 50K. What would the final pressure be if the temperature was raised to 100K?
Step 1: Write down the equation and given conditions
Example #3
P1 T1
= P2 T2
P1 T1 P2 T2
= =
= =
1 atm
50K
100K ?
Whiteboards Work in pairs
Trade-off marker every question
You have 60 seconds to calculate the answer Show all of your work! Don’t forget units!
Lift board only when prompted
The temperature of a gas is raised by 50K. Draw an arrow (up/down) to show how pressure would be
affected.
The pressure of a gas is lowered to .5 atm from STP.
Draw an arrow showing what would happen to the
temperature.
A gas is sealed in a bottle at 400K and 2 atm. If put
into a freezer at 200K, what would the new pressure be?
The pressure of CH4 (methane) gas at 10K is
increased from 2 atm to 10 atm. What is the new
pressure?
Closing Today’s Objective: I can describe how the random
collisions between gas molecules creates pressure on a surface. Standard – CH.4.a
Molecular Motion Applet
Exit Slip
1. What is pressure? a. a force that comes from the interaction of molecules in
a chemical bond b. the amount of kinetic energy in a substance
c. a quantity that can be measured in mm d. the force that a gas exerts on an object
Exit Slip 2. Which of the following factors effect the
force that is exerted on an object?
a. I only b. II only
c. II & III d. I, II and III
# of collisions
I
gas temperature
II
molecular speed
III
Exit Slip 3. Which of the following relationships is
correct? a. an increase in temperature an increase in
pressure b. a decrease in temperature an increase in kinetic
energy
c. an increase in temperature a decrease in pressure d. a decrease in temperature a increase in the
number and speed of collisions
Exit Slip 4. A soccer ball is inflated to a certain pressure
and is then heated in an oven. As it warms up the pressure increases because
a. air molecules hit the walls of the ball less frequently b. rubber in the soccer ball reacts with the air inside the
ball c. air molecules speed up and collide with the wall of the
ball more often
d. air molecules diffuse quickly out of the ball
Exit Slip 5. 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
Homework Finish practice questions
Study for the quiz!
