1. What is matter? 2. What are the three phases of matter? Setup cornell notes titled, “Gases”

Everything that has mass and takes up space is called matter.

Solid, liquid, gas

4 GASES Why do gases have different properties Than solids and liquids? Atomic composition (what atoms make up a substance) also affects physical properties.

5 Importance of Gases Airbags fill with N 2 gas in an accident.Airbags fill with N 2 gas in an accident. Gas is generated by the decomposition of sodium azide, NaN 3.Gas is generated by the decomposition of sodium azide, NaN 3. 2 NaN 3 ---> 2 Na + 3 N 22 NaN 3 ---> 2 Na + 3 N 2

6 THREE STATES OF MATTER

7 General Properties of Gases There is a lot of “free” space in a gas.There is a lot of “free” space in a gas. Gases can be expanded infinitely.Gases can be expanded infinitely. Gases fill containers uniformly and completely.Gases fill containers uniformly and completely. Gases diffuse and mix rapidly.Gases diffuse and mix rapidly.

8 Kinetic Molecular Theory Kinetic = to move Kinetic energy vs. Potential energy –Kinetic energy: object is moving –Potential energy: stored energy, is the ability of a system to do work due to its position or internal structure

9 Kinetic Molecular Theory Kinetic-molecular theory explains the different properties of solids, liquids, and gases. describes the behavior of matter in terms of particles in motion.

10 Kinetic Molecular Theory Gases consist of small particles separated by empty space. Gas particles are too far apart to experience significant attractive or repulsive forces. Gas particles are in constant random motion and do collide An elastic collision is one in which no kinetic energy is lost.elastic collision

11 Kinetic Molecular Theory Kinetic energy of a particle depends on mass and velocity.

12 Explaining the Behavior of Gases Section 12-1 Great amounts of space exist between gas particles. Compression reduces the empty spaces between particles.

13 Diffusion vs. Effusion Diffusion is the movement of one material through another.Diffusion Effusion is a gas escaping through a tiny opening.

14 DO NOW – 4/14/10 1. Draw a picture of 3 different containers with the particles that compose a gas, liguid, and solid. Which has more empty space? 2. Do gas particles… Move? Collide? Increase or decrease speed with a temperature increase? Setup Cornell Notes: “Intro to Gas Laws”

15 Objectives: By the end of the period, you should be able to…. 1. Describe the movement of gas particles 2. Define Pressure, Boyles Law, and Charles Law 3. Apply the concepts of pressure, volume, and temperature change to gaseous systems

16 Agenda Do Now Notes: “Intro to Gas Laws” Activity: outside “Ring of Ping” Exit Slip

17 Intro to Gas Laws

18 Why do our ears sometimes hurt when we are flying on airplanes? Airplane ear is the stress exerted on your eardrum and other middle ear tissues when the air pressure in your middle ear and the air pressure in the environment are out of balance. You may experience airplane ear at the beginning of a flight when the airplane is climbing or at the end of a flight when the airplane is descending. These fast changes in altitude cause air pressure changes and can trigger airplane ear

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20 What is air Pressure? PressurePressure is defined as force per unit area. Measured in atmospheres (atm) Gas particles exert pressure when they collide with the walls of their container. The more they collide with the walls of the container, the higher the pressure

21 Properties of Gases Gas properties can be modeled using math. V = volume of the gas (L)V = volume of the gas (L) T = temperature (K)T = temperature (K) –ALL temperatures MUST be in Kelvin!!! No Exceptions! n = amount (moles)n = amount (moles) P = pressure (atmospheres)P = pressure (atmospheres)

22 Pressure Pressure of air is measured with a BAROMETER (developed by Torricelli in 1643) Hg rises in tube until force of Hg (down) balances the force of atmosphere (pushing up). (Just like a straw in a soft drink) P of Hg pushing down related to Hg densityHg density column heightcolumn height

23PressureColumn height measures Pressure of atmosphere 1 standard atmosphere (atm) * = 760 mm Hg (or torr) * = inches Hg * = 14.7 pounds/in2 (psi) *HD only = kPa (SI unit is PASCAL) * HD only = about 34 feet of water!

24 What is Temperature? Temperature is a measure of the average kinetic energy (energy of motion) of the particles in a sample of matter.Temperature

25 Gas Laws Simulator Record your observations to the right

26 Activity: “The Ring of Ping” Expectations for going outside: –Absolutely NO TALKING in the hallway »1 person talks, we ALL go back to the classroom and do an activity from the book »Once we are outside, No horseplay, everyone is on task or we come back to the classroom

27 Activity: “The Ring of Ping” Ring of Ping –Form a circle: you will represent a container that has a gas inside of it –3 volunteers will be my gas particles »You will bounce off of the sides of the container and bump into one another »Follow a straight line »Stay at the same speed »Be serious and vizualize what you saw in the simulator

28 Activity: “The Ring of Ping” Container people: –When someone bumps into you, you must say “Ping” 1 volunteer will record all of the pings Time keeper

29 Exit Slip Explain the relationship you observed in our activity outside between volume, pressure, and temperature –At least 4 sentences Turn in last weeks HW: Chap 10 and 11 vocab with pictures

30 Start Homework – due Fri Read pages Copy down and define the vocabulary on page 402 Answer questions on page 410

31 Pressure Conversions A. What is 475 mm Hg expressed in atm? 1 atm 760 mm Hg B. The pressure of a tire is measured as 29.4 psi. What is this pressure in mm Hg? 760 mm Hg 14.7 psi = 1.52 x 10 3 mm Hg = atm 475 mm Hg x 29.4 psi x

32 Pressure Conversions A. What is 2 atm expressed in torr? B. The pressure of a tire is measured as 32.0 psi. What is this pressure in kPa?

33 Boyle’s Law P α 1/V This means Pressure and Volume are INVERSELY (oppositely) PROPORTIONAL if moles and temperature are constant (do not change). For example, P goes up as V goes down. P 1 V 1 = P 2 V 2 Robert Boyle ( ). Son of Earl of Cork, Ireland.

34 Boyle’s Law and Kinetic Molecular Theory P proportional to 1/V

35 Boyle’s Law A bicycle pump is a good example of Boyle’s law. As the volume of the air trapped in the pump is reduced, its pressure goes up, and air is forced into the tire.

36 Charles’s Law If n and P are constant, then V α T V and T are directly proportional. V 1 V 2 = T 1 T 2 If one temperature goes up, the volume goes up!If one temperature goes up, the volume goes up! Jacques Charles ( ). Isolated boron and studied gases. Balloonist.

37 Charles’s original balloon Modern long-distance balloon

38 Charles’s Law

39 Gay-Lussac’s Law If n and V are constant, then P α T P and T are directly proportional. P 1 P 2 = T 1 T 2 If one temperature goes up, the pressure goes up!If one temperature goes up, the pressure goes up! Joseph Louis Gay- Lussac ( )

40 Gas Pressure, Temperature, and Kinetic Molecular Theory P proportional to T

41 Combined Gas Law The good news is that you don’t have to remember all three gas laws! Since they are all related to each other, we can combine them into a single equation. BE SURE YOU KNOW THIS EQUATION! P 1 V 1 P 2 V 2 = T 1 T 2 No, it’s not related to R2D2

42 Combined Gas Law If you should only need one of the other gas laws, you can cover up the item that is constant and you will get that gas law! = P1P1 V1V1 T1T1 P2P2 V2V2 T2T2 Boyle’s Law Charles’ Law Gay-Lussac’s Law

43 Combined Gas Law Problem A sample of helium gas has a volume of L, a pressure of atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm? Set up Data Table P 1 = atm V 1 = 180 mL T 1 = 302 K P 2 = 3.20 atm V 2 = 90 mL T 2 = ??

44 Calculation P 1 = atm V 1 = 180 mL T 1 = 302 K P 2 = 3.20 atm V 2 = 90 mL T 2 = ?? P 1 V 1 P 2 V 2 = P 1 V 1 T 2 = P 2 V 2 T 1 T 1 T 2 T 2 = P 2 V 2 T 1 P 1 V 1 T 2 = 3.20 atm x 90.0 mL x 302 K atm x mL T 2 = 604 K = 331 °C = 604 K

45 Learning Check A gas has a volume of 675 mL at 35°C and atm pressure. What is the temperature in °C when the gas has a volume of L and a pressure of 802 mm Hg?

46 One More Practice Problem A balloon has a volume of 785 mL on a fall day when the temperature is 21°C. In the winter, the gas cools to 0°C. What is the new volume of the balloon?

47 And now, we pause for this commercial message from STP OK, so it’s really not THIS kind of STP… STP in chemistry stands for Standard Temperature and Pressure Standard Pressure = 1 atm (or an equivalent) Standard Temperature = 0 deg C (273 K) STP allows us to compare amounts of gases between different pressures and temperatures

48 Try This One A sample of neon gas used in a neon sign has a volume of 15 L at STP. What is the volume (L) of the neon gas at 2.0 atm and –25°C?

49 Avogadro’s Hypothesis Equal volumes of gases at the same T and P have the same number of molecules. V = n (RT/P) = kn V and n are directly related. twice as many molecules

50 Avogadro’s Hypothesis and Kinetic Molecular Theory P proportional to n The gases in this experiment are all measured at the same T and V.

51 IDEAL GAS LAW Brings together gas properties. Can be derived from experiment and theory. BE SURE YOU KNOW THIS EQUATION! P V = n R T

52 Using PV = nRT P = Pressure V = Volume T = Temperature N = number of moles R is a constant, called the Ideal Gas Constant Instead of learning a different value for R for all the possible unit combinations, we can just memorize one value and convert the units to match R. R = R = L atm Mol K

53 Using PV = nRT How much N 2 is required to fill a small room with a volume of 960 cubic feet (27,000 L) to 745 mm Hg at 25 o C? Solution Solution 1. Get all data into proper units V = 27,000 L V = 27,000 L T = 25 o C = 298 K T = 25 o C = 298 K P = 745 mm Hg (1 atm/760 mm Hg) = 0.98 atm P = 745 mm Hg (1 atm/760 mm Hg) = 0.98 atm And we always know R, L atm / mol K

54 Using PV = nRT How much N 2 is req’d to fill a small room with a volume of 960 cubic feet (27,000 L) to P = 745 mm Hg at 25 o C? Solution Solution 2. Now plug in those values and solve for the unknown. PV = nRT n = 1.1 x 10 3 mol (or about 30 kg of gas) RT RT

55 Learning Check Dinitrogen monoxide (N 2 O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23°C, what is the pressure (mm Hg) in the tank in the dentist office?

56 Learning Check A 5.0 L cylinder contains oxygen gas at 20.0°C and 735 mm Hg. How many grams of oxygen are in the cylinder?

57 Deviations from Ideal Gas Law Real molecules have volume. The ideal gas consumes the entire amount of available volume. It does not account for the volume of the molecules themselves. There are intermolecular forces. An ideal gas assumes there are no attractions between molecules. Attractions slow down the molecules and reduce the amount of collisions. –Otherwise a gas could not condense to become a liquid.

58 Gases in the Air The % of gases in air Partial pressure (STP) 78.08% N mm Hg 20.95% O mm Hg 0.94% Ar 7.1 mm Hg 0.03% CO mm Hg P AIR = P N + P O + P Ar + P CO = 760 mm Hg Total Pressure760 mm Hg

59 Dalton’s Law of Partial Pressures What is the total pressure in the flask? P total in gas mixture = P A + P B +... Therefore, P total = P H 2 O + P O 2 = 0.48 atm Dalton’s Law: total P is sum of PARTIAL pressures. 2 H 2 O 2 (l) ---> 2 H 2 O (g) + O 2 (g) 0.32 atm 0.16 atm 0.32 atm 0.16 atm

60 Dalton’s Law John Dalton

61 Health Note When a scuba diver is several hundred feet under water, the high pressures cause N 2 from the tank air to dissolve in the blood. If the diver rises too fast, the dissolved N 2 will form bubbles in the blood, a dangerous and painful condition called "the bends". Helium, which is inert, less dense, and does not dissolve in the blood, is mixed with O 2 in scuba tanks used for deep descents.

62 Collecting a gas “over water” Gases, since they mix with other gases readily, must be collected in an environment where mixing can not occur. The easiest way to do this is under water because water displaces the air. So when a gas is collected “over water”, that means the container is filled with water and the gas is bubbled through the water into the container. Thus, the pressure inside the container is from the gas AND the water vapor. This is where Dalton’s Law of Partial Pressures becomes useful.

63 Table of Vapor Pressures for Water

64 Solve This! A student collects some hydrogen gas over water at 20 degrees C and 768 torr. What is the pressure of the H 2 gas? 768 torr – 17.5 torr = torr

65 GAS DENSITY Highdensity Lowdensity 22.4 L of ANY gas AT STP = 1 mole

66 Gases and Stoichiometry 2 H 2 O 2 (l) ---> 2 H 2 O (g) + O 2 (g) Decompose 1.1 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the volume of O 2 at STP? Bombardier beetle uses decomposition of hydrogen peroxide to defend itself.

67 Gases and Stoichiometry 2 H 2 O 2 (l) ---> 2 H 2 O (g) + O 2 (g) Decompose 1.1 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the volume of O 2 at STP? Solution 1.1 g H 2 O 2 1 mol H 2 O 2 1 mol O L O 2 34 g H 2 O 2 2 mol H 2 O 2 1 mol O 2 34 g H 2 O 2 2 mol H 2 O 2 1 mol O 2 = 0.36 L O 2 at STP

68 Gas Stoichiometry: Practice! A. What is the volume at STP of 4.00 g of CH 4 ? B. How many grams of He are present in 8.0 L of gas at STP?

69 What if it’s NOT at STP? 1. Do the problem like it was at STP. (V 1 ) 2. Convert from STP (V 1, P 1, T 1 ) to the stated conditions (P 2, T 2 )

70 Try this one! How many L of O 2 are needed to react 28.0 g NH 3 at 24°C and atm? 4 NH 3 (g) + 5 O 2 (g) 4 NO(g) + 6 H 2 O(g)

71 GAS DIFFUSION AND EFFUSION diffusion is the gradual mixing of molecules of different gases.diffusion is the gradual mixing of molecules of different gases. effusion is the movement of molecules through a small hole into an empty container.effusion is the movement of molecules through a small hole into an empty container. HONORS only

72 GAS DIFFUSION AND EFFUSION Graham’s law governs effusion and diffusion of gas molecules. Thomas Graham, Professor in Glasgow and London. Rate of effusion is inversely proportional to its molar mass. HONORS only

73 GAS DIFFUSION AND EFFUSION Molecules effuse thru holes in a rubber balloon, for example, at a rate (= moles/time) that is proportional to Tproportional to T inversely proportional to M.inversely proportional to M. Therefore, He effuses more rapidly than O 2 at same T. He HONORS only

74 Gas Diffusion relation of mass to rate of diffusion HCl and NH 3 diffuse from opposite ends of tube. Gases meet to form NH 4 Cl HCl heavier than NH 3 Therefore, NH 4 Cl forms closer to HCl end of tube. HCl and NH 3 diffuse from opposite ends of tube. Gases meet to form NH 4 Cl HCl heavier than NH 3 Therefore, NH 4 Cl forms closer to HCl end of tube. HONORS only

At 100°C, water becomes water vapor, a gas. Molecules can move randomly over large distances. Below 0°C, water solidifies to become ice. In the solid state, water molecules are held together in a rigid structure. Between 0°C and 100 °C, water is a liquid. In the liquid state, water molecules are close together, but can move about freely.

Have an indefinite shape Have an indefinite volume Kinetic Molecular Theory: Molecules are moving in random patterns with varying amounts of distance between the particles.