1. 1 Chapter 6Gases 6.4 Temperature and Volume (Charles’ Law) Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2. 2 Charles’ Law In Charles’ Law, the Kelvin temperature of a gas is directly related to the volume. P and n are constant. when the temperature of a gas increases, its volume increases.

3. 3 Charles’ Law: V and T For two conditions, Charles’ Law is written V 1 = V 2 (P and n constant) T 1 T 2 Rearranging Charles’ Law to solve for V 2 T 2 xV 1 = V 2 x T 1 T 1 V 2 = V 1 x T 2 T 1

4. 4 Learning Check Solve Charles’ Law expression for T 2. V 1 = V 2 T 1 T 2

5. 5 Solution V 1 = V 2 T 1 T 2 Cross multiply to give V 1 T 2 =V 2 T 1 Isolate T 2 by dividing through by V 1 V 1 T 2 =V 2 T 1 V 1 T 2 =T 1 x V 2 V 1

6. 6 A balloon has a volume of 785 mL at 21°C. If the temperature drops to 0°C, what is the new volume of the balloon (P constant)? 1.Set up data table: Conditions 1Conditions 2 V 1 = 785 mLV 2 = ? T 1 = 21°C = 294 KT 2 = 0°C = 273 K Be sure to use the Kelvin (K) temperature in gas calculations. Calculations Using Charles’ Law

7. 7 Calculations Using Charles’ Law (continued) 2. Solve Charles’ law for V 2 : V 1 = V 2 T 1 T 2 V 2 = V 1 x T 2 T 1 V 2 = 785 mL x 273 K = 729 mL 294 K

8. 8 A sample of oxygen gas has a volume of 420 mL at a temperature of 18°C. At what temperature (in °C) will the volume of the oxygen be 640 mL (P and n constant)? 1) 443°C 2) 170°C 3) - 82°C Learning Check

9. 9 2) 170°C T 2 = T 1 x V 2 V 1 T 2 = 291 K x 640 mL = 443 K 420 mL = 443 K - 273 K = 170°C Solution

10. 10 Use the gas laws to complete sentence with 1) increases 2) decreases. A. Pressure _______, when V decreases. B. When T decreases, V _______. C. Pressure _______ when V changes from 12 L to 24 L D. Volume _______when T changes from 15 °C to 45°C Learning Check

11. 11 Use the gas laws to complete with 1) increases 2) decreases. A. Pressure 1) Increases, when V decreases. B. When T decreases, V 2) Decreases. C. Pressure 2) Decreases when V changes from 12 L to 24 L D. Volume 1) Increases when T changes from 15°C to 45°C Solution