1. Charles’ Law
Volume & temperature

2. Temperature Changes & Matter
Solids & Liquids expand/contract as temperature changes
usually very small change
Gases show large volume changes with temperature changes

3. Balloons can expand & contract with the gas

4. Jacques Charles Balloonist
1787 did experiments showing how volume of gases depends on temperature

5. How do hot air balloons work?

6. Relationship between V and T
Pressure & # moles are constant
At high temp, gas particles move faster and collide with walls more often
Pressure is constant, so volume has to increase

7. Data for Volume-Temperature
202
300 5
167
200 4
132
100 3
114 50 2 10 1
Volume (mL)
Temperature (C)
Trial

8. What did Charles do next?
Graph results

9. volume vs temperature

10. Linear Relationship Plot Volume vs ˚C : forms straight line
relationship between V and T is linear

11. Charles extrapolated graph to 0 volume
and found X-intercept is -273 ˚C

12. Hints of Kelvin scale
Charles extrapolated data to see T at which volume was 0ml
first indication that T of -273 ˚C had fundamental meaning
Why did Charles have to extrapolate his lines in this temperature range instead of collecting data?

13. Plot Volume vs. T (K) Get straight line passing through 0 point
relationship between V & T is direct

14. Charles’ Law: Verbal
volume of gas at constant pressure varies directly with its absolute temperature

15. Charles’ Law: Graphically
Plot V vs Kelvin T
Straight line passing through 0
V = kT or V = k T

16. Charles’ Law: Mathematically V = k T
V1 = V2
Given any 3 variables, can find 4th

18. Problem 1 150 mL of a gas at constant pressure
Temperature increases from 20˚C to 40˚C
What is the new volume?

19. Step 1: Convert T1 and T2 to Kelvin
Step 2: Rearrange equation:
V1 = V2 becomes V1T2 = V2
T T T1
Step 3: Substitute and solve:
(150 mL)(313 K) = mL
293 K

22. The low temperature region is always extrapolated. Why?