Pre-AP 3/7 Pick up ALL THREE PAPERS FROM THE SIDE TABLE Today we will start the gas law unit AFTER we discuss test results. You will need something to take notes on and a calculator. WE will go over pressure and temperature conversions and make a booklet for you to keep to study. There are many gas laws that you will need to learn. We wont finish until after spring break. IF YOU NEED TO RETEST, today and tomorrow are your ONLY options. My grades will be done by Wednesday.

Pre-AP 3/ Today you will need to take out your Gas Book and something to write with We will talk about KMT today and you will take notes in your book. You will also have an activity over this concept Thursday we will talk about Boyles and Charles Law AND learn to calculate those. I may perform a few demos on this day.

Characteristics of Gases The Kinetic-Molecular Theory of Matter Pressure The Gas Laws

The Kinetic-Molecular Theory of Matter

Kinetic-Molecular Theory of Matter Developed to account for the behavior of the atoms and molecules that make up matter Based on the idea that the particles of matter are always in motion

Kinetic-Molecular Theory of Gases Describes the behavior of an ideal gas –An imaginary gas that perfectly fits all the assumptions of the KM theory Based on 5 assumptions: Particles in an ideal gas… 1.have no volume. 2.undergo only elastic collisions. 3.are in constant, rapid, random, straight-line motion. 4.do not attract or repel each other. 5.have an average kinetic energy that is directly proportional to their Kelvin temperature.

Real Gases A gas that does not behave according to the assumptions of the KM theory Real gases behave most ideally –at low pressures –at high temperatures –for gases that are nonpolar

Pressure

4 factors used to describe gases: You must specify 4 measurable quantities to describe a gas: 1.Volume-liter, millileters 2.Temperature-must be in Kelvin 3.Number of molecules-moles 4.Pressure

Pressure and Force Pressure-force per unit area on a surface Gases exert pressure on any surface that they collide with, even the Earth. Air pressure in measured with a barometer. Which shoes create the most pressure?

Units of Pressure These are all equal to each other! –1 atm –760 mm Hg –760 torr – X 10 5 Pa – kPa Be able to convert between them.

Pressure Conversion Example The average atmospheric pressure in Denver, Colorado is atm. Express this pressure in (a) mm Hg and (b) kPa. a) b)

ALL TEMPERATURES MUST BE IN KELVIN FOR GASES To convert from Celsius to Kelvin: –ADD 273 Example: C to K=? C to K= To convert from Kelvin to Celsius: –SUBTRACT 273 Example: K to 0 C=? K to 0 C=

Practice: You have 15 minutes to convert the following pressure and temperature atm into kPa mmHg into atm atm into kPa kPa into torr mmHg into torr O C into Kelvin O C into Kelvin K into Celsius K into Celsius K into Celsius

Standard Temperature & Pressure Abbreviated “STP” Refers to –Temperature of 0° C –Pressure of 1 atm Values are exact

Pre-AP 3/10 Today you will need the paper from the side table, a calculator, the Boyles and Charles Law worksheet, and your BIG GAS book (you were given Monday). Please turn in the KMT picture from Tuesday if you haven’t already. Today we will do a quick station review and then we will learn to calculate Boyles and Charles Law. Tomorrow we will do a quick lab over the gas laws.

Pass the Gas Station Activity There are 6 gas stations. Four are printed for you on the front of the paper you picked up AND INCLUDE INSTRUCTIONS FOR EACH STATION. You will have to ADD TWO to the back of your paper: –Station 5: Convert the pressure and temperatures for the questions at the station –Station 6: List the five assumptions of the Kinetic Molecular Theory

The Gas Laws

Boyle’s Law Relates pressure and volume Properties are inversely proportional-as pressure increases, volume decreases. Any units may be used for pressure and volume, as long as they are the same for the 2 values.

Boyle’s Law Example 1 A sample of oxygen gas has a volume of 150. mL when its pressure is atm. What will the volume of the gas be at a pressure of atm if the temperature remains constant? P 1 =0.947 atm V 1 =150. mL P 2 =0.987 atm V 2 =?

Boyle’s Law Example 2 A helium-filled balloon contains 125 mL of gas at a pressure of torr. What pressure would the gas exert if it was allowed to expand to 135 mL? P 1 =758.2 torr V 1 =125 mL P 2 =? V 2 =760 torr

Charles’s Law Relates temperature and volume Properties are directly proportional-as temperature increases, volume increases. Any units may be used for volume, as long as they are the same for the 2 values. Temperature values must be in Kelvin. Video demonstration of Charles’s Law

Kelvin Temperature Scale Starts at a temperature equal to °C. Lowest temperature possible; called absolute zero To convert between °C and K, round to 273. –K=°C –°C=K –

Charles’s Law Example 1 A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant? V 1 =752 mL T 1 =25°C + 273=298 K V 2 =? T 2 =50°C + 273=323 K

Charles’s Law Example 2 A sample of nitrogen gas is contained in a piston with a freely moving cylinder. At 0.0°C, the volume of the gas is 375 mL. To what Celsius temperature must the gas be heated to occupy a volume of 500. mL? V 1 =375 mL T 1 =0.0°C + 273=273 K V 2 =500. mL T 2 =?

Gay-Lussac’s Law Relates temperature and pressure Properties are directly proportional-as temperature increases, pressure increases. Any units may be used for pressure, as long as they are the same for the 2 values. Temperature values must be in Kelvin.

Gay-Lussac’s Law Example 1 At 120.°C, the pressure of a sample of nitrogen is 1.07 atm. What will the pressure be at 205°C, assuming constant volume? P 1 =1.07 atm T 1 =120°C + 273=393 K P 2 =? T 2 =205°C + 273=478 K

Gay-Lussac’s Law Example 2 Before a trip from New York to Boston, the pressure in an automobile tire is 1.8 atm at 20.°C. At the end of the trip, the pressure gauge reads 1.9 atm. What is the new temperature inside the tire? P 1 = 1.8 atm T 1 =20.°C + 273=293 K P 2 =1.9 atm T 2 =?

Combined Gas Law Combine Boyle’s, Charles’s, and Gay-Lussac’s Laws Relate pressure, volume, and Kelvin temperature Any units may be used for pressure and volume as long as they are the same for the initial and final values, but temperature must be in Kelvin.

Combined Gas Law Example 1 The volume of a gas is 27.5 mL at 22.0°C and atm. What will the volume be at 15.0°C and atm? P 1 =0.974 atm T 1 =22.0°C + 273=295 K V 1 =27.5 mL P 2 =0.993 atm T 2 =15.0°C + 273=288 K V 2 =?

Combined Gas Law Example 2 A 700. mL gas sample at STP is compressed to a volume of 200. mL, and the temperature is increased to 30.0°C. What is the new pressure of the gas in Pa? P 1 = x 10 5 Pa T 1 =0.0°C + 273=273 K V 1 =700. mL P 2 =? Pa T 2 =30.0°C + 273=303 K V 2 =200. mL

AP Need…a calculator, notes, and something to write with Turn in the lab report that is DUE TODAY

4/2 Today you need The paper from the side table A calculator, something to write with WE will review Charles, Boyles, and Kinetic Molecular Theory and then learn to calculate Daltons Law, Ideal Gas Law, and discuss concepts from Avogradros Law

Dalton’s Law The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases. P total = P 1 + P Partial pressures of the gases inside the container Total pressure in container.

Dalton’s Law Example A mixture of 3 gases is at a total pressure of 6.11 atm. The partial pressure of gas A is 1.68 atm; that of gas B is 3.89 atm. What is the partial pressure of gas C? P A =1.68 atm P B =3.89 atm P C =? atm P Total =6.11 atm The total pressure in the collection bottle is equal to the sum of the partial pressures of all gases present in the bottle.

Dalton’s Law with H 2 O vapor press. When a H 2 gas is collected by water displacement, the gas in the collection bottle is actually a mixture of H 2 and water vapor. P atm = P H 2 O + P gas Look up water-vapor pressure on p.899 if given a temperature!

Dalton’s Law Example 1 Hydrogen gas is collected over water at 22.5°C. Find the pressure of the dry gas if the atmospheric pressure is 94.4 kPa. P H2 =? kPa P H2O =2.72 kPa P atm =94.4 kPa The total pressure in the collection bottle is equal to atmospheric pressure and is a mixture of H 2 and water vapor.

Dalton’s Law Example 2 A gas is collected over water at a temp of 35.0°C when the barometric pressure is torr. What is the partial pressure of the dry gas? P gas =? torr P H2O =42.2 torr P atm =742.0 torr The total pressure in the collection bottle is equal to barometric pressure and is a mixture of the “gas” and water vapor.