1. Inversely Proportional Graphing
Gas Class #2
Objective: The relationship between pressure and volume of a gas (Boyle’s Law),
Inversely Proportional Graphing

2. The relationship between pressure + volume is called
According the the KMT:
Pressure is caused by collisions of particles. More collisions makes greater the pressure
Stronger the collisions makes greater pressure.
The relationship between pressure + volume is called
INVERSELY PROPORTIONAL.

3. What is the relationship between pressure and volume? THINK
Pressure as a function of volume of a gas…
Pressure
volume

4. High Volume Low Pressure
What is the relationship between pressure and volume? THINK
Pressure as a function of volume of a gas…
Pressure
High Volume Low Pressure
High Pressure Low Volume
volume

5. Pressure X Volume = a gas constant
Inversely Proportional means as 1 variable increases, the other decreases
As pressure increases, volume decreases,
Or, as pressure decreases, volume increases.
For any sample of gas (my gas or your gas)
Pressure X Volume = a gas constant

6. 1. Your nitrogen sample has volume of 3
1. Your nitrogen sample has volume of 3.75 L It is at a pressure of 125 kPa.
What is the gas constant for this gas?

7. 1. Your nitrogen sample has volume of 3. 75 Liters
1. Your nitrogen sample has volume of 3.75 Liters. It is at a pressure of 125 kPa. What is the gas constant for this gas?
P x V = constant
(125 kPa)(3.75 L) = 469 kPa·L
Which is an odd unit (we love odd units)

8. 2. What if we change the conditions of your nitrogen gas sample, to say, 9.75 Liters. Calculate the new volume?
Hint: P X V = a constant

9. For your gas sample the gas constant it 469 kPa·L
2. What if we change the conditions of your nitrogen gas sample, to say, 9.75 Liters. What happens to the volume?
For your gas sample the gas constant it 469 kPa·L
So,
P x V = constant
P x 9.75 L = 469 kPa·L
P = 48.1 kPa

10. Think hard now. Something really amazing is coming…
Your one gas sample has a relationship between pressure and volume that is inversely proportional.
As your gas volume increased, your gas pressure decreased.
Think hard now. Something really amazing is coming…

11. For your nitrogen gas sample, the PV=C is set.
When you changed your volume, you got a new pressure, because the original P1 x V1 equaled a constant which is the same constant as your new P2 x V2
Think…
P1V1 = constant = P2V2
The original pressure volume relationship is equal to the new pressure volume relationship.
When two expressions are equal to the same thing, they are equal to each other, which is BOYLE’S LAW.

12. Boyle's Law
For any sample of gas, the pressure and volume are inversely proportional and equal to a constant, so, mathematically…
P1V1 = P2V2
The original (pressure x volume) conditions for any gas
are always equal to
the new conditions of (pressure x volume)

14. 3. A sample of neon gas is at standard pressure and liters volume. If you double the pressure, what is the new volume?
Do the math in kPa here

15. A sample of neon gas is at standard pressure and 45. 8 liters volume
A sample of neon gas is at standard pressure and liters volume. If you double the pressure, what is the new volume? SAME ANSWER USING ATM
P1V1 = P2V2
(101.3 kPa)(45.8 L) = (202.6 kPa)(X)
P1V1 = P2V2
(1 atm)(45.8 L) = (2 atm)(X)
(101.3 kPa)(45.8 L) kPa
= X
(1 atm)(45.8 L) 2 atm
= X
22.9 Liters = X
22.9 Liters = X
OF COURSE! Consistent units always!

16. 4. A thick rubber balloon has 16. 3 liters of oxygen gas inside at 1
4. A thick rubber balloon has 16.3 liters of oxygen gas inside at 1.25 atm. If the balloon can be squished (when boys stand on it) to a volume of L. What’s the new balloon pressure?

17. 4. A thick rubber balloon has 16. 3 liters of oxygen gas inside at 1
4. A thick rubber balloon has 16.3 liters of oxygen gas inside at 1.25 atm. If the balloon can be squished (when boys stand on it) to a volume of L. What’s the new balloon pressure?
P1V1 = P2V2
(1.25 atm)(16.3 L) = (P2)(12.8 L)
(1.25 atm)(16.3 L) 12.8 L
= P2
1.59 atm = P2

18. Hand in Gas HW #1 before you leave today.
Get a piece of graph paper, and a calculator now. Look at, and start: Gas Handout PV=C Finish this up for Homework tonight.