Unit 9: Kinetic Molecular Theory and Gases Chemistry Unit 9: Kinetic Molecular Theory and Gases

What is kinetic Molecular Theory (KMT)? This is the movement of molecules in a Gas.

What does KMT state? Gases particles are always in constant motion. They are always moving.

Gas particles move in a straight line until they combine with another particle or a wall.

There is no attraction between gas particles.

There is nothing but space between gas particles There is nothing but space between gas particles. Gases are easily compressed.

What happens if gas particles collide? They will simply bounce off one another and diffuse. They will not lose energy or stick to each other. These collisions are said to be elastic.

What variables affect gases? 1. Pressure (P) measured in atmospheres (atm) 2. Temperature (T) measured in Kelvin (K) 3. Volume (V) measured in Liters (L) 4. Moles (n)

PTV card

What is Standard Temperature and Pressure (STP) 1 atm and 0oC

More about Pressure? A Barometer is used to measure the amount of pressure More gas collisions increase pressure

Other pressure units you may see! 1 atm = 760 mmHg 1 atm = 760 torr 1 atm = 101.3 kPa 1 atm = 14.7 psi We can convert between units!

Let’s practice 806 mmHg =________atm 8.5 atm = ________torr 1003 torr= _______kPa

Warm Up Convert 150 kPa to atm Convert 720 atm to torr Convert 900 mmHg to psi

The Gas Laws

As one goes up, the other goes down. 1. Boyle’s Law At a constant temperature, gas pressure and volume are inversely related. As one goes up, the other goes down.

Pressure measured in Atmospheres (atm) unless otherwise specified Boyle’s Law Volume always measured in Liters (L) Pressure measured in Atmospheres (atm) unless otherwise specified

Self- Check #1 A high altitude balloon contains 30 L of Helium gas at 103atm. What is the volume when the balloon rises to an altitude where the pressure is only 25atm?

Self- Check #2 Calculate the volume of a gas (in L) at a pressure of 100kPa if its volume at 120kPa is 1500ml.

Warm Up 5.00L of a gas is at 1.08atm. What pressure is obtained when the volume is 10.0L? 2.00L of a gas is at 740.0mmHg. What is its volume at standard pressure?

As temperature goes up, so does volume. 2. Charles’s Law The volume of a gas is directly proportional to the Kelvin temperature, if the pressure is held constant. As temperature goes up, so does volume.

Temperature measured in Kelvin (K) Charles’s Law Volume always measured in Liters (L) Temperature measured in Kelvin (K) K= ̊C +273 Standard Temperature 0°C

Self- Check #3 If a sample of gas occupies 6.8 L at 325°C, what will be its volume at 25°C if the pressure does not change?

Self- Check #4 A balloon inflated in a room at 24°C has a volume of 4L. The balloon is then heated to a temperature of 58°C. What is the new volume if the pressure remains constant?

Warm Up What is the final volume of a gas that starts at 8.3L and -15 ºC, and is heated to 75 ºC?

3. Gay-Lussac’s Law The pressure of a gas is directly proportional to the temperature if the volume do not change. Temperature in Kelvin!! K= °C + 273

Self-Check #5: Let’s do together! The gas left in a used aerosol can is at a pressure of 103atm at 25°C. If this can is thrown into a fire, what is the pressure of the gas when its temperature reaches 928°C.

Self-Check #6: On your own! A gas has a pressure of 6.58 kPa at 539K. What will be the pressure at 211K, if the volume does not change?

Combines all three previous gas laws into one formula. 4. Combined Gas Law Combines all three previous gas laws into one formula.

Let’s practice Self Check # 7: Let’s do together! Self Check #8: On your own!

5. Ideal Gas Law This law assumes that gases behave ideally and are not affected by real world conditions. This law assumes, There are no intermolecular forces Particles do not take up space Where, R= 0.0821 atm/mol

Ideal gases do not exist because: Molecules do take up space There are intermolecular forces between particles Otherwise no liquids would be formed. We use this law to help to predict the behavior of real gases.

Self check #9: Let’s try together! Self Check #10: On your own!