Chemistry. Friday, February 23 rd Monday, February 26 th, 2018

Transcription

1 Chemistry Friday, February 23 rd Monday, February 26 th, 2018

2 Do-Now: Ch. 13 CN Part B 1. Write down today s FLT 2. State one part of the Kinetic Molecular Theory applied to gases 3. What are the three factors that affect gas pressure? 4. If you increase the temperature of a gas, what happens to pressure? Why? 5. If you increase the volume of a gas, what happens to pressure? Why? Take out your planner, ToC, and a calculator

3 Planner: Get ALL stamps J J J Study for Ch. 13 quiz Possible lab next week Table of Contents #1: 20. Ch. 13 CN B 21. Gases WS B

4 FLT I will be able to describe and quantify the relationships among temperature, pressure, and volume of a gas by completing Ch. 13 CN B Standard HS-PS1-5: Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

5 Ch. 13 CN B: The Gas Laws

6 Recall

7 Factors Affecting Gas Pressure Four Variables for Describing Gases: 1. Pressure (P) in kpa 2. Volume (V) in L 3. Temperature (T) in K 4. Number of Moles (n) in mol V, T, and n affect the Pressure of a gas

8 Factors Affecting Gas Pressure Direct or Inverse Relationship? Pressure and Amount (P and n)

9 Factors Affecting Gas Pressure Direct or Inverse Relationship? Pressure and Volume (P and V)

10 Factors Affecting Gas Pressure Direct or Inverse Relationship? Pressure and Temperature (P and T)

11 Gas Laws

12 The Gas Laws The gas laws tell us how gases behave The amount of change can be calculated with mathematical equations.

13 Boyle s Law

14 Robert Boyle ( ) Boyle became interested in medicine and the new science of Galileo and studied chemistry. A founder and an influential fellow of the Royal Society of London Wrote extensively on science, philosophy, and theology.

15 Boyle s Law When T is held constant, P is inversely proportional to V

16 Boyle s Law Equation: P / V = k P 1 V 1 = P 2 V 2 (T must be constant)

17 Boyle s Law Ex 1/ A balloon contains 30.0 L of He gas at 103 kpa. What is the volume of He when the balloon rises to an altitude where the pressure is only 25.0 kpa? Assume that T remains constant.

18 Ex 2/ Nitrous oxide (N 2 O) is used as an anesthetic. The pressure on 2.50L of N 2 O changes from 105 kpa to 40.5 kpa. If the temperature does not change, what will the new volume be?

19 Charles s Law

20 Jacques Charles ( ) French Physicist Part of a scientific balloon flight on Dec. 1, 1783 was one of three passengers in the second balloon ascension that carried humans This is how his interest in gases started It was a hydrogen filled balloon good thing they were careful!

21 Charles s Law When P is held constant, T is directly proportional to V

22 Charles Law Gas law problems involving temperature will always require that the temperature be in Kelvin. Reason? There will never be a zero volume, since we have never reached absolute zero. Kelvin = C and C = Kelvin - 273

23 Charles s Law Ex 1/ 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 58 C. What is the new volume if the pressure remains constant?

24 Charles s Law Ex 2/ If a sample of gas occupies 6.80 L at 325 C, what will its volume be at 25 C if the pressure does not change?

25 Gay-Lussac s Law

26 Joseph Louis Gay-Lussac ( ) French chemist and physicist Known for his studies on the physical properties of gases. In 1804 he made balloon ascensions to study magnetic forces and to observe the composition and temperature of the air at different altitudes.

27 Gay-Lussac s Law When V is held constant, P is directly proportional to T

28 Gay-Lussac s Law Ex/ A sample of nitrogen gas has a pressure of 6.58 kpa at 539 K. If the volume does not change, what will the pressure be at 211 K?

29 Combined Gas Law

30 Combined Gas Law When only n is constant, we can relate P, T, and V.

31 Combined Gas Law Ex/ 1 The volume of a gas-filled balloon is 30.0 L at 313 K and 153 kpa pressure. What would the volume be at standard temperature and pressure (STP)? (1atm = kpa)

32 Combined Gas Law Ex/ 2 A gas at 155 kpa and 25 C has an initial volume of 1.00 L. The pressure of the gas increases to 605 kpa as the temperature is raised to 125 C. What is the new volume?

33 Chemistry Tuesday, February 27 th Wednesday, February 28 th, 2018

34 Do-Now: Brainstorm Do-Now 1. Write down today s FLT 2. Are pressure and temperature directly or inversely related? 3. Sketch the graph of a direct relationship 4. Sketch the graph of an inverse relationship 5. Use a pro-talk sentence frame to tell me something about gases 6. Number underneath your do-now for a brainstorm (two rounds) 7. Take out your planner, ToC, periodic table, and a calculator

35 Planner: Finish Gas WS C J Get ALL stamps J Ch. 13 Quiz next class J Table of Contents #1: 22. Brainstorm Do-Now 23. Ch. 13 CN Part C 24. Gases WS C

36 Brainstorm Protocol 1. The goal is to generate the longest possible list as a group 2. When prompted to do so, identify who will provide the first answer 3. Then, go clockwise to the next person. 4. Do not skip people and do not say an answer for them. 5. Only say ONE answer at a time 6. Quantity over quality 7. Stay on topic 8. Pencils must be down when I say time is up 9. Lists must be exactly the same

37 FLT I will be able to calculate the value of an unknown gas variable using the ideal gas law by completing Ch. 13 Notes Part C Standard HS-PS1-5: Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

38 Ch. 13 Part C: Ideal Gases

39 Recall

40 P 1 V 1 = P 2 V 2 Boyle s Law

41 Charles s Law

42 Gay-Lussac s Law

43 Combined Gas Law

44 Factors Affecting Gas Pressure Four Variables for Describing Gases: 1. Pressure (P) in kpa 2. Volume (V) in L 3. Temperature (T) in K 4. Amount (n) in mol What about n???

45 The Ideal Gas Law

46 Ideal Gas Law PV = nrt P = Pressure (usually kpa) V = Volume (usually L) n = Amount (mol) T = Temperature (K) R = constant Allows us to calculate with moles

47 Ideal Gas Law PV = nrt R (ideal gas constant) = 8.31 (L x kpa) / (mol x K) R is constant The units MUST match in order to cancel out Wrong units = wrong answer

48 The Ideal Gas Law We now can include the AMOUNT (n) If you have an amount in your calculation, use your ideal gas law PV = nrt You can solve for any one of the variables if one is unknown n = P x V R x T

49 Ideal Gases

50 Ideal Gases We are going to assume the gases behave ideally and that they obey the Gas Laws An ideal gas does not really exist, because intermolecular forces can cause attractions between the gases Real gases = behave like ideal gases at high T and low P At low T and high P, they do not behave like ideal gases

51 Examples

52 Ex 1/ What would the volume be of 1.0 mol of an ideal gas at STP? (Recall, 1 atm = kpa)

53 Ex 2/ A cylinder of argon gas contains 50.0 L of Ar at 1860 kpa and 400. K. How many moles of argon are in the cylinder?

54 Ex 3/ Determine the volume occupied by mol of a gas at 15 C if the pressure is 81.8 kpa.

55 Recall What if you re asked for grams instead of moles for your amount? Can we convert moles to grams? I can convert from moles to grams by using MOLAR MASS You need to use your periodic table to do this

56 Ex 4/ A deep underground cavern contains 2.24 L of CH 4 gas at a pressure of 1.50 kpa and a temperature o f 315 K. How many grams of CH 4 does the cavern contain?

57 Ex 5/ A child s lungs can hold 2.20 L of O 2. How many grams of O 2 can be held at a pressure of 102 kpa and a temperature of 38 C?

58 Chemistry Thursday, March 1 st Friday, March 2 nd, 2018

59 Do-Now: Ch. 13 Quiz Review 1. Write down today s FLT 2. List two ways you can lose points on a calculation problem if you re not careful. 3. You need to calculate the number of moles of a gas. Which gas law do you use? You can write the name or the formula. 4. You need to calculate the grams of a gas. Which gas law do you use? 5. You are asked to find the pressure given two volumes and one pressure value. Which gas law do you use? Take out your planner, ToC, and a calculator

60 FLT I will be able to review the the properties and laws of gases by completing Ch. 13 Review WS Standard HS-PS1-5: Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

61 CW Review WS Work in partners or individually Write out formulas clearly Show all work and units Check sig figs Know how to: Convert from Celsius to Kelvin, ml to L, and see back of periodic table for atm to kpa ToC and/or study Ch. 13