pressure, volume and hot air

1. Gas Laws: Pressure, Volume,
and Hot Air
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2. Introduction
This interactive lesson will introduce
three ways of predicting the behaviour of
gases: Boyle’s Law, Charles’ Law, and
the Ideal Gas Law.
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3. Navigation
Throughout this lesson, you will use buttons at
the bottom right corner of the page to navigate.
Takes you to the next page
Takes you to the previous page
Takes you to the Main Menu
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4. Main Menu
Basic
Terminology
Boyle’s Law
Charles’ Law
Ideal Gas Law
Review of all four lessons
Review
Lesson 1
Lesson 2
Lesson 3
Lesson 4

5. Lesson 1: Basic Terminology
This lesson reviews terms
used to describe the
properties and behavior of
gases.
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6. Opening thoughts…
Have you ever:
Seen a hot air balloon?
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7. Opening thoughts…
Have you ever:
Seen a hot air balloon?
Had a soda bottle spray all over you?
Baked (or eaten) a nice, fluffy cake?
These are all examples of gases at work!
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8. Properties of Gases
You can predict the behavior of gases
based on the following properties:
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Pressure
Volume
Amount (moles)
Temperature
Lets review each of these briefly…

9. NEXT
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Pressure
Volume
Amount (moles)
Temperature
You can predict the behavior of gases
based on the following properties:

10. Pressure
Pressure is defined as the force the gas
exerts on a given area of the container in
which it is contained. The SI unit for
pressure is the Pascal, Pa.
• If you’ve ever inflated a tire,
you’ve probably made a
pressure measurement in
pounds (force) per square inch
(area).
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11. NEXT
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Pressure
Volume
Amount (moles)
Temperature
You can predict the behavior of gases
based on the following properties:

12. Volume
Volume is the three-dimensional space inside
the container holding the gas. The SI unit for
volume is the cubic meter, m3. A more common
and convenient unit is the liter, l.
Think of a 2-liter bottle of soda to get
an idea of how big a liter is.
(OK, how big two of them are…)
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13. NEXT
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Pressure
Volume
Amount (moles)
Temperature
You can predict the behavior of gases
based on the following properties:

14. Amount (moles)
Amount of substance is tricky. As we’ve already
learned, the SI unit for amount of substance is the mole,
mol. Since we can’t count molecules, we can convert
measured mass (in kg) to the number of moles, n, using
the molecular or formula weight of the gas.
By definition, one mole of a substance contains
approximately 6.022 x 1023 particles of the
substance. You can understand why we use mass
and moles!
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15. NEXT
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Pressure
Volume
Amount (moles)
Temperature
You can predict the behavior of gases
based on the following properties:

16. Temperature
Temperature is the measurement with which you’re
probably most familiar (and the most complex to
describe completely). For these lessons, we will be
using temperature measurements in Kelvin, K.
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The Kelvin scale starts at Absolute 0, which
is -273.15°C. To convert Celsius to Kelvin,
add 273.15.

17. How do they all relate?
Some relationships of gases may be
easy to predict. Some are more subtle.
Now that we understand the factors that
affect the behavior of gases, we will
study how those factors interact.
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18. How do they all relate?
Some relationships of gases may be
easy to predict. Some are more subtle.
Now that we understand the factors that
affect the behavior of gases, we will
study how those factors interact.
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Let’s go!

19. Lesson 2: Boyle’s Law
This lesson introduces Boyle’s
Law, which describes the
relationship between pressure and
volume of gases.
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20. Boyle’s Law
 This law is named for Charles Boyle, who
studied the relationship between pressure,
p, and volume, V, in the mid-1600s.
 Boyle determined that for the same amount
of a gas at constant temperature,
p * V = constant
 This defines an inverse relationship:
when one goes up, the other
comes down.
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pressure
volume

21. Boyle’s Law
 This law is named for Charles Boyle, who
studied the relationship between pressure,
p, and volume, V, in the mid-1600s.
 He determined that for the same amount of
a gas at constant temperature,
p * V = constant
 This defines an inverse relationship:
when one goes up, the other
comes down.
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pressure
volume

22. What does Boyle’s Law mean?
p * V = constant
Suppose you have a cylinder with a piston in the
top so you can change the volume. The cylinder
has a gauge to measure pressure, is contained so
the amount of gas is constant, and can be
maintained at a constant temperature.
A decrease in volume will result in increased
pressure.
Hard to picture? Let’s fix that!
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23. Boyle’s Law at Work…
Doubling the pressure reduces the volume by half. Conversely, when the
volume doubles, the pressure decreases by half.
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24. Application of Boyle’s Law
 Boyle’s Law can be used to predict the
interaction of pressure and volume.
 If you know the initial pressure and volume,
and have a target value for one of those
variables, you can predict what the other will
be for the same amount of gas under
constant temperature.
 Let’s try it!
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25. Application of Boyle’s Law
p1 * V1 = p2 * V2
p1 = initial pressure
V1 = initial volume
p2 = final pressure
V2 = final volume
If you know three of the four, you can
calculate the fourth.
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26. Application of Boyle’s Law
p1 * V1 = p2 * V2
p1 = 1 KPa
V1 = 4 liters
p2 = 2 KPa
V2 = ?
Solving for V2, the final volume equals 2 liters.
So, to increase the pressure of 4 liters of gas from 1
KPa to 2 KPa, the volume must be reduced to 2 liters.
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27. Boyle’s Law: Summary
 Pressure * Volume = Constant
 p1 * V1 = p2 * V2
 With constant temperature and amount
of gas, you can use these relationships
to predict changes in pressure and
volume.
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28. Lesson 2 Complete!
This concludes Lesson 2 on Boyle’s Law!
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Click the Main Menu button below, then
select Lesson 3 to learn about how
temperature fits in.

29. Lesson 3: Charles’ Law
This lesson introduces Charles’
Law, which describes the
relationship between volume and
temperature of gases.
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30. Charles’ Law
 This law is named for Jacques Charles, who
studied the relationship volume, V, and
temperature, T, around the turn of the 19th
century.
 He determined that for the same amount of
a gas at constant pressure,
V / T = constant
 This defines a direct relationship:
an increase in one results in an
increase in the other.
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volume
temperature

31. What does Charles’ Law mean?
V / T = constant
Suppose you have that same cylinder with a piston
in the top allowing volume to change, and a
heating/cooling element allowing for changing
temperature. The force on the piston head is
constant to maintain pressure, and the cylinder is
contained so the amount of gas is constant.
An increase in temperature results in increased
volume.
Hard to picture? Let’s fix it (again)!
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32. As T increases V increases

33. Charles’ Law: V1/T1 = V2/T2

34. Application of Charles’ Law
 Charles’ Law can be used to predict the
interaction of temperature and volume.
 If you know the initial temperature and
volume, and have a target value for one of
those variables, you can predict what the
other will be for the same amount of gas
under constant pressure.
 Let’s try it!
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35. Application of Charles’ Law
V1 / T1 = V2 / T2
V1 = initial volume
T1 = initial temperature
V2 = final volume
T2 = final temperature
If you know three of the four, you can
calculate the fourth.
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36. Application of Charles’ Law
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V1 / T1 = V2 / T2
V1 = 2.5 liters
T1 = 250 K
V2 = 4.5 liters
T2 = ?
Solving for T2, the final temperature equals 450
K.
So, increasing the volume of a gas at constant
pressure from 2.5 to 4.5 liters results in a
temperature increase of 200 K.

37. Charles’ Law: Summary
 Volume / Temperature = Constant
 V1 / T1 = V2 / T2 or V1T2 = V2T1
 With constant pressure and amount of
gas, you can use these relationships to
predict changes in temperature and
volume.
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38. Lesson 3 Complete!
This concludes Lesson 3 on Charles’ Law!
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39. Lesson 4: Ideal Gas Law
This lesson combines all the
properties of gases into a
single equation.
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40. Ideal Gas Law
Combining Boyle’s and Charles’ laws allows for
developing a single equation:
P*V = n*R*T
P = pressure
V = volume
n = number of moles
R = universal gas constant (we’ll get to that in a
minute…)
T = temperature
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41. Ideal Gas Law
P*V = n*R*T
This is one of the few equations in chemistry that you
should commit to memory!
By remembering this single equation, you can predict
how any two variables will behave when the others are
held constant.
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42. Gas Constant
 The Ideal Gas Law as presented includes
use of the Universal Gas Constant.
 The value of the constant depends on the
units used to define the other variables.
 For the purposes of this lesson, we will use
the equation only to predict gas behavior
qualitatively. Specific calculations and units
will be part of our classroom work.
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43. Putting p*V=n*R*T to Work
 After using Boyle’s and Charles’ law for predicting
gas behavior, use of the Ideal Gas Law should be
relatively straightforward.
 Use NASA’s Animated Gas Lab to explore the
interaction of these variables on gas behavior.
 Follow the directions on the page for changing
values for the variables.
 When you’re finished, click the Back button on your
browser to return to this lesson.
 Link to site: Animated Gas Lab
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44. Ideal Gas Law: Summary
 P*V = n*R*T
 Learn it!
 Use it!
 This single equation can be used to
predict how any two variables will
behave when the others are held
constant.
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45. Lesson 4 Complete!
This concludes Lesson 4 on the Ideal Gas Law!
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Click the Main Menu button below, then select
Review to try some questions based on these
lessons.

46. Review
This review contains multiple choice questions on the material
covered by Lessons 1 – 4. Select an answer by clicking the
corresponding letter.
If you choose an incorrect answer, you will be given feedback and a
chance to try again. If you want to return to a lesson to review the
material, click on the Main Menu button, then select the lesson.
When you’re ready to complete the review again, go back to the Main
Menu and click the Review button.
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47. Question 1
Based on Boyle’s Law (p * V = constant) or the Ideal Gas Law
(p*V=n*R*T), when the number of moles (n) and temperature
(T) are held constant, pressure and volume are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
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48. Question 1 is Correct!
Based on Boyle’s Law (p * V = constant) or the Ideal Gas Law
(p*V=n*R*T), when the number of moles (n) and temperature
(T) are held constant, pressure and volume are:
a. Inversely proportional: if one goes up, the other
comes down.
Decreasing volume increases
pressure. Increasing volume
decreases pressure.
pressure
volume
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49. Try Question 1 again…
Based on Boyle’s Law (p * V = constant) or the Ideal Gas Law
(p*V=n*R*T), when the number of moles (n) and temperature
(T) are held constant, pressure and volume are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
You selected b. While pressure and volume are related,
it is not a direct proportion. Try again!
TRY
AGAIN
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50. Try Question 1 again…
Based on Boyle’s Law (p * V = constant) or the Ideal Gas Law
(p*V=n*R*T), when the number of moles (n) and temperature
(T) are held constant, pressure and volume are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
You selected c. Pressure and volume are related. Is the
relationship inverse or direct?
TRY
AGAIN
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51. Question 2
Based on Charles’ Law (V / T = constant) or the Ideal Gas
Law (p*V=n*R*T), when the number of moles (n) and pressure
(p) are held constant, volume and temperature are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
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52. Try Question 2 again…
Based on Charles’ Law (V / T = constant) or the Ideal Gas
Law (p*V=n*R*T), when the number of moles (n) and pressure
(p) are held constant, volume and temperature are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
You selected a. While volume and temperature are
related, it is not an inverse proportion. Try again!
TRY
AGAIN
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53. Question 2 is Correct!
Based on Charles’ Law (V / T = constant) or the Ideal Gas
Law (p*V=n*R*T), when the number of moles (n) and pressure
(p) are held constant, volume and temperature are:
b. Directly proportional: if one goes up, the other goes
up.
Increasing temperature
increases volume. Decreasing
temperature decreases
volume.
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volume
temperature

54. Try Question 2 again…
Based on Boyle’s Law (p * V = constant) or the Ideal Gas Law
(p*V=n*R*T), when the number of moles (n) and temperature
(T) are held constant, pressure and volume are:
a. Inversely proportional: if one goes up, the other comes
down.
b. Directly proportional: if one goes up, the other goes up.
c. Not related
You selected c. Pressure and volume are related. Is the
relationship inverse or direct?
TRY
AGAIN
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55. Question 3
Lets put the Ideal Gas Law (p*V=n*R*T) to some practical
use. To inflate a tire of fixed volume, what is the most
effective way to increase the pressure in the tire?
a. Increase the force pressing on the outside of the tire.
b. Increase the temperature of the gas (air) in the tire.
c. Increase the amount (number of moles) of gas in the tire.
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56. Try Question 3 again…
Lets put the Ideal Gas Law (p*V=n*R*T) to some practical
use. To inflate a tire of fixed volume, what is the most
effective way to increase the pressure in the tire?
a. Increase the force pressing on the outside of the tire.
b. Increase the temperature of the gas (air) in the tire.
c. Increase the amount (number of moles) of gas in the tire.
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TRY
AGAIN
While increasing the load in the car might increase the
force on the tires, it would prove to be a difficult way to
adjust tire pressure. Try again!

57. Try Question 3 again…
Lets put the Ideal Gas Law (p*V=n*R*T) to some practical
use. To inflate a tire of fixed volume, what is the most
effective way to increase the pressure in the tire?
a. Increase the force pressing on the outside of the tire.
b. Increase the temperature of the gas (air) in the tire.
c. Increase the amount (number of moles) of gas in the tire.
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TRY
AGAIN
Increasing the temperature of the air in the tire would definitely increase
pressure. That is why manufacturers recommend checking air pressures
when the tires are cold (before driving). But how would you increase
temperature without damaging the tire? Is there a more practical
solution?

58. Question 3 is Correct!
Lets put the Ideal Gas Law (p*V=n*R*T) to some practical
use. To inflate a tire of fixed volume, what is the most
effective way to increase the pressure in the tire?
a. Increase the force pressing on the outside of the tire.
b. Increase the temperature of the gas (air) in the tire.
c. Increase the amount (number of moles) of gas in the tire.
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When you inflate a tire with a pump, you are adding air, or
increasing the amount of air in the tire. This will often result in
a slight increase in temperature because a tire is not a
controlled environment. Such deviations and quirks will be
discussed in class!
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59. Mission complete!
 You have completed the lessons and
review. Congratulations!
 You should now have a better
understanding of the properties of gases,
how they interrelate, and how to use them to
predict gas behavior.
 Please click on the button below to reset the
lesson for the next student. Thanks!
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