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

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.

Charles’ Law: V and T For two conditions, Charles’ Law is written V1 = V2 (P and n constant) T1 T2 Rearranging Charles’ Law to solve for V2 T2 x V1 = V2 x T1 T1 T1 V2 = V1 x T2 T1

Learning Check Solve Charles’ Law expression for T2. V1 = V2 T1 T2

Solution V1 = V2 T1 T2 Cross multiply to give V1T2 = V2T1 Isolate T2 by dividing through by V1 V1 V1 T2 = T1 x V2 V1

Calculations Using Charles’ Law 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 1 Conditions 2 V1 = 785 mL V2 = ? T1 = 21°C = 294 K T2 = 0°C = 273 K Be sure to use the Kelvin (K) temperature in gas calculations.

Calculations Using Charles’ Law (continued) 2. Solve Charles’ law for V2: V1 = V2 T1 T2 V2 = V1 x T2 T1 V2 = 785 mL x 273 K = 729 mL 294 K

Learning Check 1) 443°C 2) 170°C 3) - 82°C 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

Solution 2) 170°C T2 = T1 x V2 V1 T2 = 291 K x 640 mL = 443 K 420 mL = 443 K - 273 K = 170°C

Learning Check 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

Solution 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