1. Gas Law Essential Questions
How do we know what is happening to atoms and molecules if we can not see them?
How is what I am seeing related to what is happening on a molecular level?
How do I represent or model the behavior or particles on a nanoscopic level?

2. Gas Law Challenges How can you shrink a marshmallow?
What happens to divers when they breathe underwater?
How can you inflate a balloon without blowing it up?
How does a hot air balloon work?
How can you extinguish a candle without blowing it out?
Why does the bottle feel hot?
Why does the can feel cold?
How can you crush a can without touching it?
Why does shaving cream inflate in a vacuum?
How can you burn a piece of paper without fire?
How can you boil water without heating it up?
How can you get an egg inside a bottle?

3. Scientific Laws observed mathematical measured Second theories NOT
Scientific laws describe something we have repeatedly _________. Usually these laws can be written as simple _________________ relationships. In physics for example, the relationship “F = m x a” has been ___________ and confirmed so many times that it is called Newton’s ________ Law and it is part of the Theory of Classical Mechanics.
observed
mathematical
measured
Second
However, laws and _________ are not the same. A theory does ______ become a law. In fact, a theory is the scientific _________ behind the laws we observe. The general public often misuses the word “theory” to mean something that “is not yet ____________”.
theories
NOT
reasoning
proven

4. Scientific Theories 1600s Einstein Kinetic Molecular Theory of Gases
Scientists however, use the word theory with great confidence because it means the best possible explanation based on repeated experimentation. Starting in the ________ and for another 200 hundred years, early chemists were doing experiments on gases and developed many gas laws. At first, there was no “theory” to explain these laws. However, these scientists developed equations that consistently predicted the pressure, volume, and temperature of a gas. Eventually, __________ (1905) provided experimental evidence for the _______ _________ _______ __ ______ .
1600s
Einstein
Kinetic Molecular Theory of Gases

5. Theoretical Assumption Meaning for the behavior of gases?
Kinetic Molecular Theory
Theoretical Assumption
Meaning for the behavior of gases?
1. Gases particles are very far apart compared to their actual size.
2. Collisions between particles or the walls of their container are elastic
3. Gas particles are in continuous, rapid, random motion
4. There are no forces of attraction between gas particles
5. Temperature is related to average kinetic energy of all the particles
Shape and Volume are variable, Low density and compressible
Elastic means there is no loss of energy
Very high kinetic energy and expand to fill their container
Collide and travel in straight lines (like in pool)
Particles moving at different speeds, higher temperature means higher average speed

6. There are three main properties of gases that we will study:
Property
Pressure
Volume
Temperature
Definition
Standard
Units
Descrip-tion
Force per unit area on the surface of an object
Amount of cubic units than an object occupies
Average kinetic energy of particles in an object
Atmospheres
atm
Liters or mL
(1 cm3 = 1 mL)
Kelvin
K = °C +273
Number of collisions with the walls of the container
Amount of space that the gas particles take up
Average speed of the gas particles

7. Changing P V T Imagine that you are gas molecule inside a box…
If I move faster then I will collide [ more OR less ] with the walls of the container.
If my box gets smaller then I’ll collide [ more OR less ] with the walls of the container.

8. Changing P V T
If my box stays the same, but I am colliding with the walls less, I must be moving [ slower OR faster ]
If my box gets bigger, but my number of collisions stays the same, I am moving [ slower OR faster ]
If my speed and # of collisions stays the same, then my box or volume must be staying the ________
SAME

9. Gas Law Equations P V VT PT T P V Inverse Direct Direct Boyle’s Law
NAME
Variables that Change?
Held Constant?
Combined
Gas Law
Equation
Mathematical
Relationship
Sketch of Graph
Boyle’s Law
Charles’s Law
Gay-Lussac’s Law
P V VT PT T P V
Inverse
Direct
Direct

10. Changing PVT
Assuming the pressure and volume are constant, explain what must happen to the temperature of a gas.
(Words to use: space, number of collisions, speed)
Assuming the pressure is constant means that the number of collisions between particles and the walls of the container are remaining the same. If the volume is constant then the amount of space must also be staying the same. This means that the average speed of the particles (which is the temperature) must be the same also. For example, if the temperature decreased then the particles would slow down and the number of collisions or the amount of space they take up would also have to decrease in order to compensate (adjust).

11. Gas Law Algebra P2 V2 V1 V1 V1 P1 T2 P2 P2 P2 T1 P2 = P1 T2 P1 = T1 =
Write Boyle’s Law
and ____ is constant
Solve for P1 in terms of the other variables.
Rearranged Equation
P1 =
P2 V2 V1 V1 V1 T
Write Gay-Lussac’s Law
and ___ is constant
Solve for T1 in terms of the other variables.
Rearranged Equation
T1 =
T1 P2 = P1 T2
P1 T2 P2 P2 P2 V

12. P V T tool
INVERSE
DIRECT
DIRECT

13. Problem #1 ? T Boyle’s = V2 P2 P2 0.947 atm 0.987 atm 150.0 mL V2 =
A sample of oxygen gas has a volume (V1) of mL when its pressure (P1) is atm. What will the volume (V2) of the gas be at a pressure (P2) of atm? The temperature is held constant. T
Boyle’s V2 P2 P2 =
0.947 atm
0.987 atm
V2 =
P1 V1 P2
0.947 atm x mL
0.987 atm ?
150.0 mL
V2 = 144 mL

14. Remember to convert to: K = °C + 273
2. A sample of neon gas occupies a volume (V1) of 752 mL at (T1) 25 °C. What volume (V2) will the gas occupy at (T2) 50 °C if the pressure remains constant?
 Think before you solve…
What variable is held constant? _____
This means I need ___________ Law.
What variable am I solving for? _____
 Equation
Re-arrange your equation for the unknown
(You’ll need to cross-multiply )
 List Data
 Solve by plugging in your data
Check your answer =
V1 =
T1 =
V2 =
T2 =
Remember to convert to: K = °C + 273 P
Charles’s V2
T1 V2 = V1 T2 T1 T1 ?
752 mL
V2 = V1 T2 T1
= 752 mL x 323 K
298 K
50°C = 323 K
25°C =
298 K
815 mL