Gases Chapter 11 (and 10)

Transcription

1 Gases Chapter 11 (and 10)

2 Warm up 1. What is a gas? 2. What is pressure? 3. What units are used to measure pressure?

3 Properties of Gas Expansion: indefinite shape and volume Fluidity: particle move pass each other Low density: often floats Compressibility: can press particle closer together Diffusion and effusion: Diffusion: mixing of gas by random motion Effusion: gas particles passing through tiny opening

4 Properties of Liquids: fluid Relatively higher density Relative incompressibility Ability to diffuse: constant random movement of particles causes them to mix slower than gas Surface tension Evaporate and boil

5 Properties of water: Forms hydrogen bonds high heat of vaporization: must be hot to evaporate Low melting point: stays as a liquid Less dense as a solid

6 Properties of Solids Definite shape and volume Highest density Incompressibility Low rate of diffusion

7 Can you rate solid, liquid and gas from low to high for each property? Density Compressibility Diffusion Boiling point Melting point

8 Phase Diagram: shows critical points in the change of states of mater: temperature and pressure both affect the state of matter Ch 10 pg 347

9 Kinetic Molecular Theory of Gas Ch 10 pg Parameters for an ideal gas 1. Made of tiny particles that are relatively far apart 2. Collisions between the particles does not lose energy 3. Particles are in continuous rapid random motion 4. There is no attraction between particles 5. Temperature of gas depends on average kinetic energy of particles Kinetic molecular theory only applies to ideal gases. Most gases are only nearly ideal if pressure is not too high and temperature is not to low

10 Pressure: force/unit area Caused by the collisions of molecules with the walls the container SI units = Newton/meter 2 = 1 Pascal (Pa) 1 standard atmosphere = kpa 1 atm = 760 mmhg = 760 torr So of 1 atm = 760 mmhg = kpa 1 mmhg = 1 torr barometer is a device used to measure atmospheric pressure

11 Continuing Ch 11 Gases notes Pascal is the SI unit of pressure 1 atm = 760 mmhg = kpa 1 mmhg = 1 torr

12 1 atm = 760 mmhg = kpa Pressure Conversions Given: atmospheric pressure = atm Unknown: a. pressure in mm Hg b. pressure in kpa a atm 760 mm Hg = atm 631 mm Hg kpa b atm = atm 84.1 kpa

13 Factors that affect gases 1. Kinetic theory 2. Pressure 3. Volume 4. Temperature *affect pressure

14 Factors that affect gases 1. Kinetic Theory As collisions increases, pressure will increase. particles travel in straight line paths until they collide with other particles or wall of the container. Pressure is measured Unit = kilopascal Standard pressure is 101kPa

15 Factors that affect gases 2. Pressure (amount of gas) As # of gas particles increases (without increasing volume), pressure increases and collisions increases Filling a tire with air Gas naturally flows from high to low pressure Ex: Aerosol cans pressure inside can is higher than pressure outside

16 Relationship Between Pressure, Force, and Area

17 Factors that affect gas 3. Volume As volume decreases, collisions increase and so pressure increases Volume is measured in liters

18 Factors that affect gas 4. Temperature As temperature increases, energy Increases so collisions Increase causing pressure of a gas to Increase Temp is measured in Kelvin K = o C Standard temp = 0 o C Kelvin is used because 0 in an equation is problematic Absolute zero: not heat/energy: 0 o K

19 STP: Standard Temperature and Pressure P = 1 atmosphere, 760 torr, kpa T = 0ºC, 273 Kelvins (K) convert to Kelvin: ºK = ºC The molar volume of an ideal gas is 22.4L at STP

20 Dalton s law of partial pressure total pressure of a mixture of gases is the sum of their partial pressures P total = P 1 + P 2 + P 3 Ex B: pg 367 Oxygen gas from decomposition of KClO 3 was collected by water displacement. The barometric pressure was torr and the pressure of the water vapor was 17.5 torr, find the partial pressure of oxygen. Patm = Po 2 + PH 2 O 731torr =Po torr torr = torr

21 HW Ch 10 Section review Pg 332 # 1-2, 5-6 Pg 351# 1-5

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23 Boyle s Law: volume of the gas varies inversely with pressure P 1 (V 1 ) = P 2 (V 2 ) Boyle s Law defines the relationship between pressure and volume Pressure of a gas increases as the volume decreases when temp. is constant Ex C pg 370 A sample of oxygen gas has a volume of ml when its pressure is atm. What will the volume of the gas be at a pressure of atm if the temperature remains constant? Given: V 1 of O 2 = ml, P 1 of O 2 = atm, P 2 of O 2 = atm Unknown: V 2 of O 2 in ml PV P 1 V 1 = P 2 V 2 = atm x 150.0mL = 144mL O V P 2

24 Boyle's Law clip Cartesian diver demo Fish bubbles Breathing Boyle's Law and breathing watch? v=nb1acbid6qa

25 Sample Boyle s Law Problem A hot air balloon contains 30.0 L of He gas at 103 kpa. What is the volume of the balloon when it decreases in pressure to 25.0 kpa due to its rise in altitude? Assume the temp remains constant. What do we know? What are we trying to find? What law applies? Solve Does your answer make sense? (124 L) P 1 (V 1 ) = P 2 (V 2 )

26 More problems to practice N 2 O is used as an anesthetic. The pressure of gas changes from 105 kpa to 40.5 kpa. The ending volume is 6.48 L. What was the original volume due to this change in pressure if temp. is held constant. (2.50 L) A gas with a volume of 4.00L is at a pressure of 1.30 atm. The gas is allowed to expand to 12.0 L. What is the new pressure in the container if the temp. is held constant? (0.433 atm)

27 Charles Law: Volume is directly proportional to temperature. V 1 / T 1 = V 2 / T 2 V 1 T 1 = V 2 T 2 As the temperature of the enclosed gas increases, the volume Increases when pressure is held constant. Don t forget! K = ºC + 273, (temp can t be zero) Ex D pg 372 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? Given: V 1 of Ne = 752 ml, T 1 of Ne = 25 C = 298 K, T 2 of Ne = 50 C = 323 K Unknown: V 2 of Ne in ml V T = V 1 2 T 1 2 V 2 = VT 1 2 T 1 752mL x 323K 298 K = 815mL Ne

28 Charles' Law clip Microwave popcorn Warming/cooling balloon over flask Demos

29 V 1 = V 2 T 1 T 2 A balloon inflated in a room at 24 C has a volume of 4.00 L. The balloon is then heated to a temperature of 50 C. What is the new volume of the balloon if the pressure of the room remains constant throughout the experiment? (4.35 L) Exactly 5.00 L of air at C is warmed. If the new volume of the balloon is 8.36 L, to what temperature in C was it heated? Assume pressure is constant. (99.9 C) If a sample of gas occupies a volume of 6.80 L at 325 C, what will its volume be at 25.0 C if the pressure does not change? (3.39 L) Sample Charles Law Problem

30 Whose law? Balloon test ttps:// v=jzsajbakgk4 Imploding drum SN5j1ogk Marshmallows in a vacuum

31 Gay-Lussac s Law: The pressure of a gas is directly proportional to Kelvin temperature P 1 /T 1 = P 2 /T As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant. P T = P T Ex E pg 373 The gas in a container is at a pressure of 3.00 atm at 25 C. Directions on the container warn the user not to keep it in a place where the temperature exceeds 52 C. What would the gas pressure in the container be at 52 C? Given: P 1 of gas = 3.00 atm, T 1 of gas = 25 C = 298 K, T 2 of gas = 52 C = 325 K Unknown: P 2 of gas in atm P T = P 1 2 T 1 2 P 2 = PT 1 2 T atm x 325K 298 K = 3.27 atm

32 Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C #1 Pg 372 sample D #1,2 Pg 374 sample E #1,2,3 Pg 375 sample F # : Pg 385 sample I #1-2 More Practice: (do not do now ) Try pg 375 section review # 2-4 and pg 385 section review #3,5,6

33 Sample Gay-Lussac s Law Problems The pressure in an empty aerosol can is 103 kpa. If the can is thrown into a fire and increased in temp. from 25.0 C to 928 C what will the resulting pressure be. Volume is kept constant since the size of the can does not change. (415 kpa) Think about the tires on your car. Why do you suppose that tire manufacturers recommend checking the air pressure in your ties before driving more than a mile? The pressure in a car tire is 198 kpa at 27 C. After a long drive the pressure in the tire has increased to 225 kpa. What is the temp of the air in the tire? Assume tire volume is constant. (341 K)

34 Another problem.. A sample of nitrogen gas has a pressure of 0.58 atm at 539K. If the volume is kept constant and the temp. decreases to 211K, what is the new pressure? (0.23 atm)

35 Summary Boyle s Law: P 1 (V 1 ) = P 2 (V 2 ) Indirectly related Charles Law: V 1 / T 1 = V 2 / T 2 Directly related Gay-Lussac s Law: P 1 /T 1 = P 2 /T 2 directly related Warm up: Who s law is demonstrated in each? 1. Bag of chips pop when brought from a higher to lower altitude. 2. Burning gun powder increases the pressure until a cannon explodes. 3. Car tires become slightly smaller in the snow. 4. Pumping up a bike tire by adding air. 5. Heating corn kernels until they pop.

36 Combined Gas Law: Boyle s Law: P 1 (V 1 ) = P 2 (V 2 ) Charles s Law: PV T = PV T 1 2 Gay-Lussac s Law: Gas law only works when the amount of gas is constant.

37 Combined Gas Law Example F pg 375 A helium-filled balloon has a volume of 50.0 L at 25 C and 1.08 atm. What volume will it have at atm and 10.0 C? Given: V 1 of He = 50.0 L T 1 of He = 25 C = 298 K T 2 of He = 10 C = 283 K P 1 of He = 1.08 atm P 2 of He = atm Unknown: V 2 of He in L PV T = PV T 1 2 V 2 = PVT PT atm x 50.0LHe x 283K 0.855atm x 298 = 60.0L He

38 Sample Combined Gas Law Problems A volume of gas is 30.0L at 313K and 153 kpa. What will the new volume be at standard temp. and pressure (STP)? (39.5 L) A 5.00L air sample has a pressure of 1.07 atm at a temp of C. If the temp is raised to 102 C and the volume expands to 7.00L, what will the new pressure be? (1.29 atm)

39 Ideal Gas Law: PV = nrt Combined gas law only works when amount of gas is constant. You can t use the combined gas law to compute how many moles you have of a gas at a fixed volume and a known temperature and pressure, so to calculate that the Ideal Gas Law is used It is expressed by the following equation: PV = nrt Solve for R when PVT and n= standard values.

40 Ideal Gas Law: PV = nrt P = Pressure (kpa or atm) V = Volume (L) n = amount of gas in moles (mol) R = ideal gas constant (determined from STP values) 8.31 L kpa/k mol L atm/k mol T = Temperature (K) Ex I pg 385 What is the pressure in atmospheres exerted by a mol sample of nitrogen gas in a 10.0 L container at 298 K?

41 Ex I pg 385 What is the pressure in atmospheres exerted by a mol sample of nitrogen gas in a 10.0 L container at 298 K? Given: V of N 2 = 10.0 L n of N 2 = mol T of N 2 = 298 K Unknown: P of N 2 in atm PV = nrt P = nrt V P (0.500 mol)( L atm)(298 K) = = 1.22 atm 10.0 L

42 Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C practice #1 Pg 372 sample D practice #1,2 Pg 374 sample E practice#1,2,3 Pg 375 sample F practice# : Pg 385 sample I practice#1-2 Homework: Pg 375 section review # 1-6

43 Problems to practice A child s lungs can hold 2.20 L of air. How many moles of air do her lungs hold at a pressure of 102 kpa and a body temp. of 37 C? ( mol) Use a value of 29.0 g/mol for the molar mass of air and calculate the amount of GRAMS of air. (2.53 g)

44 Warm up: which law/equation do you use, then solve 1. A volume of gas is 30.0L at 313K and 1.5 kpa. What will the new volume be at standard temp. and pressure (STP)? 39.5L 2. A child s lungs can hold 2.20 L of air. How many moles of air do her lungs hold at a pressure of 102 kpa and a body temp. of 37 C? mol

45 Ch 11 notes Summary so far.. Boyle s Law: P 1 (V 1 ) = P 2 (V 2 ) Charles Law: V 1 / T 1 = V 2 / T 2 Gay-Lussac s Law: P 1 /T 1 = P 2 /T 2 Combined Gas Law: Ideal Gas Law: PV = nrt What does each variable stand for?

46 P = Pressure (kpa or atm) V = Volume (L) n = amount of gas in moles (mol) R = ideal gas constant (determined from STP values) 8.31 L kpa/k mol L atm/k mol T = Temperature (K) Review of Ch 11 notes from last class

47 What law should you use to solve? Combined Ideal Combined Ideal Combined A gas has a volume of ml at minus C and torr. What would the volume of the gas be at C and torr of pressure? At what temperature will moles of neon gas occupy liters at 1.95 atmospheres? What is the pressure of a gas at K if its original pressure was atm and K. A sample of argon gas at STP occupies 56.2 liters. Determine the number of moles of argon and the mass in the sample L of a gas is collected at 25.0 C and mmhg. What is the volume at STP?

48 Why is this lady s explanation not really correct? v=hhtm4k_tlfi

49 Warm up: which law/equation do you use, then solve 1. A volume of gas is 30.0L at 313K and 1.5 kpa. What will the new volume be at standard temp. and pressure (STP)?.395L 2. A child s lungs can hold 2.20 L of air. How many moles of air do her lungs hold at a pressure of 102 kpa and a body temp. of 37 C? mol

50 Real vs. Ideal Gases Ideal gases must follow all the gas laws at all conditions of pressure and temp. have no volume and there is not attraction between particles in the gas no such gas exists Real gases have volume and there is often attraction between particles. Real gases act most like ideal gases at STP

51 Avogadro's law Equal volumes of gas at the same temp. and pressure contain equal # of particles At STP: standard molar volume 1mole = 22.4 liters Ex G page 381 a. What volume does mole of gas occupy at STP? 1.53 L b. What quantity of gas, in moles in 2.21L at STP mol

52 Ex: 2 Ideal Gas Law and molar volume a. A deep underground cavern contains 2.24 x 10 6 L of CH 4 (methane gas) at a pressure of 1500 kpa and a temp of 315 K. How many moles of CH 4 are in the cavern? (1.27 x 10 6 mol) b. How many GRAMS in the cavern? c. How many LITERS are in the cavern at STP? Recall that moles can be converted to liters or grams using the molar road map when the number of moles are known.

53 STP and not STP Ex 3: A 30.6 g sample of gas occupies 44.8 L at STP. What is the molar mass of this gas? 15.3 g/mol Ex 4: 96.0 g. of a gas occupies 48.0 L at mm Hg and 20.0 C. What is its molecular weight? 700mmHg (1atm/760mmHg) =.921atm PV=nRT (.921)(48)=n(.0821)(293) n = mol 96.0 g / mol = 52.2 g/mol

54 Diffusion and Effusion Diffusion: mixing of gas by random motion Effusion: gas particles passing through tiny opening

55 Ch 11.3 section review - put in classwork section of notebook Ch 11.3, answer pg 385 section review #1, 2, and 5

56 classwork Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C practice #1 Pg 372 sample D practice #1,2 Pg 374 sample E practice#1,2,3 Pg 375 sample F practice# : Pg 385 sample I practice#1-2 4/2/15 Ch 11.3 section review pg 385 section review #1, 2, and 5 Goals: 1. Finish classwork CH 11 practice problems 2. Ch 11.4 section reviw 3. Ch 11 study guide

57 Explain this Whose law?? Pack Mate watch until 1:10 Liquid nitrogen balloons How do you fix a dented ping pong ball? start at 0:45 sec stop at 1:54 You give ME a practical application of one of the gas laws

58 Ch 11.3 Answers 1. Equal volumes of gas at the same temperature and pressure will contain equal numbers of particles. Volume and # of molecules vary directly with STP, 1mole=22.4 liters 2. 78mL atm or pka (oxygen is diatomic, if not diatomic, 5.24atm)

59 Whose Law? Gay Lussac Law

60 Whose law? BOYLE

61 Whose Law? Charles Law

62 Name the law Combined Gas Law

63 Name the law Allows for respiration! Boyle s Law

64 Common Core Standards Physical Science HS-PS1-3. Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. CA State Standards

65 Common Core Standards Physical Science HS- PS1-6. Refine the design of a chemical system by specifying a change in condi<ons that would produce increased amounts of products at equilibrium.* HS-PS2-6. Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.*

66 HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

67 After Test Science Fair Project: revise background research or work on procedures (pg5-6 in packet) or Read Ch pg Take notes (be sure to include all vocabulary) Title the notes Ch 12 Solutions Put in notes section of notebook (if you can) or write on binder paper