Presentation on theme: "BIG CHILL PROJECT – 5% Goal: Build a container that keeps an ice cube from melting for the longest period of time. Must be 15.0cm x 15.0cm x 15.0cm."— Presentation transcript:
1 BIG CHILL PROJECT – 5%Goal: Build a container that keeps an ice cube from melting for the longest period of time.Must be 15.0cm x 15.0cm x 15.0cm or smaller.Must operate at room temperature with no electricity.Must be an original creation.
2 BIG CHILL PROJECTMust have a opening and chamber big enough to accommodate an ice cube.
3 BIG CHILL PROJECTGrade is two parts: 1. Construction - 50 pts 2. Efficiency - 50 pts Bonus points for being a top three finisher in your class, the best design in your class, ice cube lasting longer than 8 hours, and a parent signature on the blue form. DUE THURSDAY MARCH 14
4 OBJECTIVESDescribe the effect on a gas by a change in the amount of gas (moles), the pressure of gas, the volume of gas, and the temperature of gas.Be able to perform calculations using Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law.Be able to use Dalton’s Law of Partial Pressures in a calculationDistinguish between real and ideal gases. Be able to tell how real gases differ from ideal gases.State the ideal gas law and know what each symbol stands forPerform calculations using the ideal gas law and the combined gas law.State and use Graham’s Law of Diffusion.Be able to calculate gas stoichiometry problems (volume – volume, mass – volume, volume – mass).Be able to calculate density and molecular mass using the ideal gas law formula.
6 PRESSURE (Chapter 12) Pressure is the force per unit area. Gases exert pressure when they hit the walls of their container.To measure air pressure, you might use a barometer or a manometer. A barometer measures atmospheric pressure. A manometer measures the internal pressure of an enclosed gas.
7 PRESSUREThere is pressure exerted by the atmosphere. At sea level this pressure is equal to one atmosphere.
9 PRESSURE Pressure is measured in a variety of units. ABBREVIATIONCOMPARE TO 1 ATMKilopascalkPa101.3 kPaMillimeters of mercurymmHg760.0 mmHgTorrtorr760.0 torrAtmosphereatm1.0 atmPounds per square inch*psi14.7 psi*We will use all of these but psi.
10 VIDEODISC Chapter 2 – Racing Hot Air Balloons Why is it easier for pilots to control the vertical direction of a balloon’s flight than the horizontal direction?Why did Julie say that a thermal is not a good word for balloonists?
11 GASES (Chapter 12) Physical Properties of Gases: Gases have mass. Gas particles do not attract or repel each other.It is easy to compress gases.Gas molecules are in constant motionGases fill their containers completelyDifferent gases can move through each other quite rapidly.Gases exert pressure.The pressure of a gas depends on its temperature and volume.
12 GASESRemember that gases consist of very small particles, the particles have large distances between them, they are in constant, rapid, random motion and have elastic collisions.Actual gases (in real life) do not obey all the suppositions stated in the kinetic-molecular theory.In order to accurately measure a gas sample, you must know the quantity of particles (moles), pressure, temperature, and volume of a gas.
13 THE GAS LAWS (Chapter 13) Boyle’s Law: V and P; inversely proportional.Charles’ Law: T and V; directly proportional.Gay-Lussac’s Law: P and T; directly proportional.Avogadro’ Principle: moles and P or V; directly proportional.
14 THE GAS LAWS DEMOS – Boyle’s Law Chapter 7 – Breathing and Boyle’s Law 1. Why does the balloon expand?2. What does this demo have to do with breathing?3. Have you ever heard the phrase “nature abhors a vacuum?” What do you think it means?Cartesian DiverWorld record diveBalloon and bottleArtificial lung
16 BOYLE’S LAWTHE LAW: For a given mass of gas, at a constant temperature, the volume varies inversely with the pressure: P1V1 = P2V2PRACTICE:The pressure in a 9.0 L balloon is 2.1 atm. If the volume is reduced to 5.0 L, what will the resulting pressure be? (Temperature does not change.)V1 = 9.0 L V2 = 5.0 LP1 = 2.1 atm P2 = ? atmP1V1 = P2V2 P2 = P1V1 =V2
17 REMINDER EVERY TIME you do a gas laws problem: Write what you know and what you are trying to findWrite the formulaPlug in the numbers with units and solve with the correct number of sig figs.
20 You must use the Kelvin temperature scale! CHARLES LAWTHE LAW: The volume of a fixed mass of a gas is directly proportional to its KELVIN temperature if the pressure is constant. If pressure is kept constant, then volume must change to keep temperature the same.V1 = V2T1 T2You must use the Kelvin temperature scale! K = °CPRACTICE:The temperature of a sample of gas is K. The gas’ volume is 25.0 L. What will be the new volume of the gas if the temperature is dropped to K?V1 = 25.0 L V2 = ? L V2 = T2V1 =T1 = K T2 = K T1
21 GAS LAWS Videodisc – Chapter 5 - Imploding Can 1. Why did the can implode?2. How does the demonstration you just saw relate to a barometer?3. How is a vacuum seal created on a jar of homemade preserves?Egg in a bottleBulb with pressure gauge
23 You must use Kelvin temperature scale! GAY-LUSSAC’S LAWTHE LAW: An increase in temperature increases the frequency of collisions between gas particles. In a given volume, raising the KELVIN temperature also raises the pressure.P1 = P2T1 T2 You must use Kelvin temperature scale!PRACTICE:The temperature of a sample of gas is K. The gas’ pressure is 1.4 atm. What will be the new pressure of the gas be if the temperature is dropped to K?P1 = 1.4 atm P2 = ? atm P2 = T2P1 =T1 = K T2 = K T1
24 REMINDER EVERY TIME you do a gas laws problem: Write what you know and what you are trying to findWrite the formulaPlug in the numbers with units and solve with the correct number of sig figs.
25 DO NOW Pick up handout – due tomorrow Copy problem set info - due Feb. 25Ch. 12 #1, 2Ch. 13 #1, 2, 5, 6, 8, 9, 11,16, 21, 26, 27, 36, 38, 39, 42Paper towel drive ends Friday, 3:30.Balloons and Cans lab due Feb. 19.
30 AVOGADROS’S PRINCIPLE Particles of different gases vary greatly in sizes. But size is not a factorThe Law: equal volumes of gases at the same temperature and same pressure contain equal number of particles.In gas law problems moles is designated by an “n”.One mole of a gas has a volume of 22.4 L (dm3) at standard temperature and pressure (STP). It also has 6.02 x 1023 particles of that gas.
32 DALTON’S LAW OF PARTIAL PRESSURES THE LAW: The sum of the partial pressures of all components of a gas mixture is equal to the total pressure of the gas mixture.Ptotal = P1 + P2 + P3 + PPRACTICE (Easy Type):What is the atmospheric pressure if the partial pressures of nitrogen, oxygen, and argon are mm Hg, mm Hg, and mm Hg, respectively?Ptotal = P1 + P2 + P3 Ptotal =
34 DALTON’S LAW OF PARTIAL PRESSURES PRACTICE (Hard Type):A quantity of oxygen gas is collected over water at 8C in a L vessel. The pressure is 84.5 kPa. What volume would the DRY oxygen gas occupy at standard atmospheric pressure (101.3 kPa) and 8C. (The dry gas pressure of water at 8C is 1.1 kPa)T1 = 8ºC T2 = 8ºCV1 = 0.353L V2 = ?P1 = 84.5 kPa – 1.1 kPa = 83.4 kPa P2 = kPaYou must correct the pressure so that you can have the DRY gas without the water pressure added in. P1V1 = P2V2 V2 = P1V1 =P2
35 GAS LAWS Videodisc – Chapter 9 Scuba Diving Think about your lungs as a flexible 6-liter container full of a gas at STP. How would lung volume change at a depth of 30 meters?Why not increase the oxygen to 100% and go really deep?What are the bends? How do divers avoid them?
36 From the Boyle’s, Charles’, and Gay-Lussac’s laws, we can derive the COMBINING THE LAWSFrom the Boyle’s, Charles’, and Gay-Lussac’s laws, we can derive theCombined Gas Law:P1V1 = P2V2T1 T2Mnemonic: Potato and Vegetable on top of the Table
37 COMBINED GAS LAW PRACTICE: The volume of a gas measured at 75.6 kPa pressure and 60.0°C is to be corrected to correspond to the volume it would occupy at STP. The measured volume of the gas is 10.0 cm3.P1 = 75.6 kPa P2 = kPa P1V1 = P2V2V1 = L V2 = ? T1 T2T1 = K T2 = 273 KV2 = P1V1T2 = ___________________________T1P2
38 STANDARDS T = 0°C = 273 K V = 22.4 L (at STP) P = 1.00 atm = 101.3 kPa = mm Hg = torrRemember only kPa has limited sigfigs.
39 COMBINED GAS LAWPRACTICE: Correct the volume for a gas at 7.51 m3 at 5.0°C and 59.9 kPa to STP.
40 “R” is the universal gas constant. IDEAL GAS LAWIdeal Gas Equation:PV = nRT“R” is the universal gas constant.
41 UNIVERSAL GAS CONSTANTS R = L• atm mol • K R = 62.4 L•mm Hg mol • K R = 62.4 L • torr R = 8.31 L • kPaWhy are there four constants?
42 IDEAL GAS LAW Remember: Always change the temperature to KELVINS and convert volume to LITERSCheck the units of pressure to make sure they are consistent with the “R” constant given or convert the pressure to the gas constant (“R”) you want to use.
43 IDEAL GAS LAW PRACTICE: How many moles of a gas at 100.0°C does it take to fill a 1.00 L flask to a pressure of 1.50 atm?V = 1.00 L T = 100.0°C = KP = 1.50 atm R = atm•Ln = ? mol•KPV = nRTn = PV = ____________________________ =RT
44 IDEAL GAS LAW PRACTICE: What is the volume occupied by 9.45g of C2H2 at STP? Hint - convert grams to moles.....9.45g C2H2 1 mol C2H2 = mol26.04g C2H2P = 1.00 atm R = atm•LV = ? mol•Kn = mol T = 273.0K
45 PRACTICE P = 1.00 atm T = 273K V = ? R = 0.0821 L· atm N = 0.363mol mol· KV = nRT = (0.363mol)(273K)( L· atm)=P (1.00 atm) (mol· K)= 8.14L
46 GRAHAM’S LAW OF EFFUSION or DIFFUSION (Chapter 12) The rate of diffusion/effusion is inversely proportional to the square root of its molar mass under identical conditions of temperature and pressure.If two bodies of different masses have the same kinetic energy, the lighter body moves faster.
47 DEMO Anise and Cinnamon What can we assume about the temperatures of the two oils?How is temperature related to KE?How doe the KE of the two oils compare?What is the formula for KE?
48 CALCULATIONS KE = ½mv2 ½ mava2 = ½ mcvc2 ½ mava2 = ½ vc2 mc ½ ma = ½ vc2mc va2ma = vc2mc va2
49 GRAHAM’S LAW OF EFFUSION or DIFFUSION (Chapter 12) Rate (velocity) a = Formula mass b Rate (velocity) b Formula mass a Compare ammonia and hydrochloric acid: velocity NH3 = 36.45g/mol velocity HCl 17.04g/mol = NH3 is 1.46 times faster than HCl
50 REAL vs. IDEAL GASESThe ideal gas equation, PV = nRT, is simple to use and accurately predicts gas behavior in many everyday situations.Under very high pressure, real gases have trouble compressing completely. The ideal gas law fails. Ideal gases have no volume, but real gases do.
51 REAL vs. IDEAL GASESAt very low temperatures, attractive forces between real gas molecules become significant and real gases liquefy.The ideal gas law can be used under ordinary conditions only.
52 GAS STOICHIOMETRY VOLUME 1 mol 22.4 L @ STP 1 mole 1 mole We are now going to add to our MOLE CITY diagram, adding volume of a mole of gas.VOLUME mol STP1 mole molePARTICLES MOLE MASS6.02 x molar mass
53 GAS STOICHIOMETRY PRACTICE Determine the volume in 2.0 moles of H2. ?? volume = 2.0 mol H L H2 = mol H2= 45 L H2
54 GAS STOICHIOMETRYB. Determine the volume in 10.3 moles of CO2. ?? volume =
55 GAS STOICHIOMETRYC. Determine the moles in 251 L of O2. ?? moles =
56 GAS STOICHIOMETRYD. What volume of hydrogen gas is needed for the complete reaction between nitrogen gas and hydrogen gas to produce ammonia? You are given 5.0L of nitrogen gas. This problem involves not a “mass to mass” problem but a “volume to volume” problem. The balanced equation is N2 + 3H2 2NH3
58 GAS STOICHIOMETRYE. What volume of oxygen gas is needed for the complete reaction between oxygen gas and potassium chloride to produce potassium chlorate? You are given 45.0g KCl. This problem involves not a “volume to volume” problem but a “mass to volume” problem.The balanced equation is 2KCl + 3O2 2KClO3
60 HOMEWORK Ch. 13 #40-41, 43-44 due tomorrow Graham’s Law handout due tomorrow.Quiz is now Monday March 3.Dry Ice lab will be Friday.Giant Problem set due March 4.Test is March 5.
61 Get out Gas Diffusion lab ANALYSIS and CONCLUSION:1. Calculate the ratio of the distance moved. Since both gases moved through the glass tube in the same amount of time, the distances the gases moved can be used as a measure of the rates of diffusion of the gases. Substituting the distance (d) each gas moved for the velocity of the gas. Determine the ratio of the distance moved. Show your work. This is the experimental ratio. USE THE CLASS AVERAGE FOR THIS.d1 = m2 HCl = distance NH3 traveled d m1 NH distance HCl traveled
62 ANALYSIS and CONCLUSION 2. Determine the true rate of diffusion for ammonia (m1)to hydrochloric acid (m2). Use the masses from the periodic table. Write the formula and show your work.3. How close is your experimental value to the molecular mass ratio? Calculate your percent error. Write the formula and show your work.
63 GAS LAW PROBLEMS DIRECTIONS Be sure to write:What you know and where you are going (V1, V2, P1, P2, T1, T2, etc.)The formulaRewrite the formula to solve for the unknown and fill in the known data.Show all units.Write the correct answer with sigfigs and units.
64 GAS LAW PROBLEMS DIRECTIONS For stoichiometry:write what you know and where you are goingWrite the balanced equation if not given.Convert to moles, do the mole ratio, and convert to what is asked for.
65 Gas Law Problems #11. A sample of oxygen gas occupies a volume of mL at torr pressure. What volume will it occupy at torr pressure?
66 Gas Laws #1 AnswerV1 = 250.0mL V2 = ? P1 = torr P2 = torr Boyle’s Law V2 = V1P1 = (250.0mL)(740.0torr) = P2 (800.0torr) = = mL
67 DETERMINING MOLAR MASS We can use the ideal gas equation to calculate the molar mass of a gas from laboratory measurements.The molar mass formula isMolar mass, MM = mass, m/moles, nSo, n (moles) is equal to:moles, n = mass, mMolar mass, MM
68 DETERMINING MOLAR MASS So, if n = m/M, substitute it in the formula. The ideal gas equation can be written as PV = mRT MM = mRT MM or P V
69 PRACTICEWhat is the molar mass of a gas if dm3 has a mass of 7.202g at 110°C and kPa?MM = T =V = P =m = R =MM = mRT =P V
70 DETERMINING DENSITYThis modified version of the ideal gas equation can also be used to solve for the density of a gas.PV = nRT bcomes D = PMMRT
71 DETERMINING DENSITYMM = mRT P V rewrite with m/V on one side PMM = m RT V D = m = PMM or D = PMM V RT RT
72 PRACTICEFind the density of NH3 in g/L at 752 mm Hg and 55°C. MM = T = R = P = D = PMM = RT
73 PRACTICE1. Calculate the molar mass, MM, of a gas if dm3 has a mass of 75.0 g at 100°C and 95 kPa.
74 PRACTICE1. Calculate the molar mass, M, of a gas if dm3 has a mass of 75.0 g at 100°C and 95 kPa.MM = ? T = 373KV = 150.0L P = 95kPam = 75.0g R = 8.31 L kpamol KMM = mRT = (75.0g)(373K)(8.31L kpa)P V (95kPa)(150.0L)(mol K)= = 16g/mol
75 PRACTICE2. Determine the density of chloroform gas, CHCl3 if a sample massing is collected in a flask with at 37°C and a pressure of 728 mm Hg.
76 PRACTICE2. Determine the density of chloroform gas, CHCl3 if a sample massing is collected in a flask with at 37°C and a pressure of 728 mm Hg.MM = g/mol T = 310KR = L mmHg P = 728mmHgmol KD = PMM = (728mmHg)(119.37g)(mol K)RT (310K)(62.4 L mmHg)(mol)= = 4.5g/L
77 GAS LAWS QUIZ –MONDAY There will be six problems. Could be any from this list:Boyles / Charles / Gay-LussacDalton’s Law of Partial PressureCombined Gas LawIdeal Gas LawGraham’s Law of DiffusionGas StoichiometryExtra Credit is Density or Molar Mass problem
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