1. Gas Laws

2. Properties of Gases Expand to completely fill their container
Take the shape of their container
Low density – mass divided by volume. Take up much more space than their mass.
Much less than solid or liquid state
Compressible
Mixtures of gases are always homogeneous

3. Characteristics of Gases
Gases can be compressed.
low volume = lots of empty space
Gases undergo diffusion & effusion

4. Factors That Affect Gases
Pressure – the force that a gas exerts on a given area of a container.
Volume – the space inside a container holding the gas.
Concentrations (Moles) – amount of the gas. We can convert to mass using molecular weight.
Temperature – the average speed of the gas particles.

5. Pressure Conversions KEY UNITS AT SEA LEVEL 101.3 kPa (kilopascal)
1 atm
760 mm Hg
760 torr
14.7 psi
*These are all equal to each other!

6. Pressure Conversions A) 2.5 atm = ? kPa 2.5 atm 101.3 kPa 1 atm
B) 200 torr = ? mmHg
200 torr mmHg torr
= 200 mmHg
C) 35 psi = ? atm
D) 1200 torr = ? atm
35 psi 1 atm psi
= 2.4 atm
1200 torr 1 atm torr
= 1.6 atm

7. Temperature Conversions
Always use absolute temperature (Kelvin) when working with gases. ºF ºC K
-459 32
212
-273
100
273
373
K = ºC + 273

8. Temperature Conversions
A) 10 ºC = ? K
B) 300 K = ? ºC
10 ºC =
283 K
300 K – 273 =
27 oC

9. Standard Temperature & Pressure
STP
STP
Standard Temperature & Pressure
273 K
1 atm

10. Boyles’ Law
If the temperature remains constant, the volume and pressure vary inversely
i.e. if Pressure ↑, then Volume ↓; and vice versa
P1 V1 = P2 V2

11. Boyle’s Law (cont.)

12. Boyles’ Law Example
If a gas has a volume of 200 ml at 800 mmHg pressure, calculate the volume of the same gas at 765 mmHg.
P1= 800mmHg
V1= 200ml
P2 =765mmHg
V2=?
Formula P1 V1 = P2 V2

13. Formula P1V1 = P2V2
Plug in values
800 mmHg x 200 ml = 765 mmHg x V2
Solve V2= 800mmHg x 200ml
765mmHg
V2 = ml

14. Charles’ Law
If the pressure remains constant, the volume and temperature vary directly
i.e. if Temperature ↑, then Volume ↑; and vice versa
V1 V2
T1 T2 =

15. Charles’ Law (cont.)

16. Charles’ Law Example
The volume of a gas at 20°C is 500ml. Find its volume at standard temperature if the pressure is held constant.
T1= 20°C +273
V1= 500ml
T2 = 0°C +273
V2=?

17. Formula V1 = V2 T1 T2 Plug in values 500ml V2 293K 273K
Solve V2= 273K x 500ml
293K
V2 = ml =

18. Gay Lussac’s Law
If the volume remains constant, the temperature and pressure vary directly
i.e. if Pressure ↑, then Temperature ↑. *And vice versa
P1 P2
T1 T2 =

19. Pressure and Temperature (cont.)

20. Gay-Lussac’s Example
A steel tank contains a gas at 27°C and a pressure of 12 atm. Determine the gas pressure when the tank is heated to 100°C.
T1= 27°C +273
P1= 12 atm
T2 = 100°C +273
P2=?

21. P1 = P2 T1 T2 Plug in values 12 atm P2 300K 373K
Solve P2 = 373K x 12atm
300K
P2 = atm =