Heat • Energy transferred due to differences in

temperature Temperature

• Measure of the average kinetic energy of particles composing a material

Pressure • Force per unit area

Volume • The amount of space a material occupies

Pressure and volume are indirectly related

Pressure and 1/volume are directly related

1. A balloon initially occupies 12.4 L at 1.00 atm. What will be the volume at 0.800 atm?

2. A sample of gas expands from 10.0 L to 30.0 L. If the initial pressure was 1140 mm Hg, what is the new pressure?

Using Boyles law

Calculate: A balloon contains 40.0 L of a gas at 101.3 kPa. What is the volume of the gas when the balloon is brought to an altitude where the pressure is only 10.0 kPa? (Assume that the temperature remains constant.)

Temperature and volume are directly related At constant pressure

Absolute zero• Theoretically, point at which all motion stops.

• The temperature at which volume of a gas becomes zero when the plot of temperature vs. volume is extrapolated.

1. Calculate the decrease in temperature when 2.00 L at 20.0°C is compressed to 1.00 L.

2. A gas occupies 900.0 mL at a temperature of 27.0°C. What is the volume at 132.0°C?

Temp and pressure are directly related

Absolute zero• The temperature at which the pressure of a gas

becomes zero when a plot of pressure versus temperature for a gas is extrapolated

-273C = 0 K or K = C + 273

1. Consider a container with a volume of 22.4 L filled with a gas at 1.00 atm at 273 K. What will be the new pressure if the temperature increases to 298K?

2. A container is initially at 47 mm Hg and 77K (liquid nitrogen temperature.) What will the pressure be when the container warms up to room temperature of 25C?

3. A thermometer reads a pressure of 248 Torr at 0.0C. What is the temperature when the thermometer reads a pressure of 345 Torr?

STP (standard temperature and pressure)

T = 273K (which is 0°C)P = 1 atm, 101.3 kPa, 760 mmHg, 760 torrV = 22.4 L (one mole of gas)

FormulaP1V1 = P2V2

T1 T2

10.0 cm3 volume of a gas measured 75.6 kPa and 60.0C is to be corrected to correspond to the volume it would occupy at STP.

The Kinetic Molecular Theory describes IDEAL gases Most gases approximate ideal gases and the model works great for most gases.  Some REAL gases need adjustments 

• Real gases experience electrostatic attractions. • Real gases have volume

PV = nRT • P = pressure-measured in atm, kPa, mmHg, torr• V = volume - usually measured in L • T = temperature in K• n = number of moles (“mol”)• R = “universal gas constant”

Calculate R if pressure is in atm: (most common) (1 atm)(22.4 L) = 0.0821 atm*L/K*mol(273 K)(1mol)

Calculate R if pressure is in kPa: (most common) (101.3 kPa)(22.4 L) = 8.312 kPa*L/K*mol(273 K)(1mol)

Calculate R if pressure is in torr or mm Hg: (rarely used)(760 torr)(22.4 L) = 62.36 torr*L/K*mol(273 K)(1mol)

(760 mmHg)(22.4 L) = 62.36 mmHg*L/K*mol(273 K)(1mol)

Calculate the temperature of 0.500 moles of a gas occupying a volume of 20.0 L with a pressure of 99.9 kPa.

(99.9 kPa)(20 L) = 480.75 K(8.312 kPa*L/K*mol)(.5 mol)

Calculate the moles of a gas occupying a volume of 500.0 mL with a temperature of 25.5C and a pressure of 755 torr.

(755 torr)(.5 L) = 0.0203 mol(298.5 K)(62.36 torr*L/K*mol)

Calculate the volume of 1.00 mol of H2 at STP

STP = 0C 273 K and 1.00 atmP = 1 atmV = ?n = 1 molR = 0.0821 L-atm/mol-KT = 273K PV = nRT nRT/P = V (1 mol)(.0821L-atm/mol-K)(273 K) =

1 atmThat number should look familiar! It is the volume of one mole of any gas at STP. The number from the mole map comes from the ideal gas law.

22.4 L

End