Temperature and Volume General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 7 Gases 7.4 Temperature and Volume (Charles’ Law) Lectures © 2013 Pearson Education, Inc.

Charles’s Law Charles’s law states that, the Kelvin temperature of a gas is directly related to the volume of the gas, P and n are constant, and as the temperature of a gas increases, the molecules move faster and its volume increases to maintain constant P. 2

Charles’s Law: V and T Charles’s law states that when the temperature of a gas increases, making the molecules move faster, the volume of the gas must increase to maintain constant pressure. 3

Charles’s Law: V and T A sample of neon gas has a volume of 3.1 L and a temperature of 12 ˚C. Find the new volume (L) of the gas if the temperature rises to 32 ˚C. Assume the pressure and amount of gas remain constant. Step 1 Organize the data in a table of initial and final conditions. Analyze the Problem. Conditions 1 Conditions 2 Know Predict T1 = 12 °C + 273 = 285 T1 = 32 °C+ 273 = 305 K T increases V1 = 3.1 L V1 = ? V increases 4

Charles’s Law: V and T A sample of neon gas has a volume of 3.1 L and a temperature of 12 ˚C. Find the new volume (L) of the gas if the temperature rises to 32 ˚C. Assume the pressure and amount of gas remain constant. Step 2 Rearrange the gas law equation to solve for the unknown quantity. 5

Charles’s Law: V and T A sample of neon gas has a volume of 3.1 L and a temperature of 12 ˚C. Find the new volume (L) of the gas if the temperature rises to 32 ˚C. Assume the pressure and amount of gas remain constant. Step 3 Substitute values into the gas law equation and the table. 6

Learning Check 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)? 7

Solution 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)? Step 1 Organize the data in a table of initial and final conditions. Analyze the Problem. Conditions 1 Conditions 2 Know Predict V1 = 785 mL V2 = ? V decreases T1 = 21 °C = 294 K T2 = 0 °C = 273 K T decreases 8

Solution 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)? Step 2 Rearrange the gas law equation to solve for the unknown quantity. Step 3 Substitute values into the gas law equation and the table. 9