100% EVERYDAY. Name: Period: Date: UNIT 11: Gases Lesson 1: Vapor Pressure! Do Now: 1. Which process decreases enthalpy? (1) boiling of water (2) Melting of copper (3) Condensation of ethanol (4) Sublimation of iodine By the end of today, you will have an answer to: How is it possible for water to boil at room temperature? 2. At STP, which 2.0-gram sample of matter uniformly fills a 340-milliliter closed container? (1) Br 2 (3) KCl(aq) (2) Fe(NO 3) 2 (4) Xe(g) Catalyzing thoughts: Examine the pictures below of two flasks. Annotate (ask questions, jot down observations), what you see in BOTH pictures. Vapor pressure means:
100% EVERYDAY. How can we use this concept of vapor pressure to help us understand boiling? Pot with no flame Pot with flame (warming) 1 flame lots of bubbles (boiling) No Heat Heat + 5 minutes Heat + 10 minutes Notes on boiling: A substance boils when the equals the of the liquid Atmospheric pressure (Standard Pressure) is found on Table A kpa (kilopascals) or atm (atmosphere) Boiling Point: The temperature at which the atmosphere pressure = the vapor pressure Why is this important? Table H: What is the Title? X-Axis? Y-Axis? Questions 1. What is the vapor pressure of ethanoic acid at 50 C? 75 C? What is the boiling point of ethanoic acid at standard pressure? 2. At what temperature would ethanol have a vapor pressure of 50 kpa?. --Water has a higher boiling point than propanone. Compare the Intermolecular forces for both water and propanone. If the pressure of the atmosphere was 60 kpa, what would the boiling point of ethanol be? 3. At what temperature does propanone have a pressure of 70 kpa?
100% EVERYDAY. Name: Pd: Date: CW 11.1 Vapor Pressure (Table H) Explain what is happening in this picture to cause boiling. Make sure your answers includes both vapor pressure and atmospheric pressure. Thought Questions: 1. In terms of vapor pressure, why does heating a substance cause it to boil? 2. How can we actually cause a substance to boil at room temperature? 3. Why do you think it takes longer to cook spaghetti when you boil water in Denver (low atmospheric pressure) than it does in New York City (standard atmospheric pressure)? In-class Practice using Table H: Directions: Answer the following questions based on your knowledge of chemistry. 3) At 50 C, which substance exerts the most vapor pressure? 4) What is the vapor pressure of water at 105 C? Name: Pd: Date: CW 11.1 Vapor Pressure (Table H) Explain what is happening in this picture to cause boiling. Make sure your answers includes both vapor pressure and atmospheric pressure. Thought Questions: 1. In terms of vapor pressure, why does heating a substance cause it to boil? 2. How can we actually cause a substance to boil at room temperature? 3. Why do you think it takes longer to cook spaghetti when you boil water in Denver (low atmospheric pressure) than it does in New York City (standard atmospheric pressure)? In-class Practice using Table H: Directions: Answer the following questions based on your knowledge of chemistry. 3) At 50 C, which substance exerts the most vapor pressure? 4) What is the vapor pressure of water at 105 C?
5) A sample of ethanoic acid at 100 C has a vapor pressure of 6) What is the vapor pressure of ethanol at 75 C? 7) At what temperature does ethanol have a vapor pressure of 50kPa? 8) At what temperature does ethanoic acid have a vapor pressure of 45kPa? 9) At what temperature does water have a vapor pressure of 110kPa? 10) Find the boiling point of propanone. 11) Find the vapor pressure of ethanol at 75 C. 12) At 50. C and standard pressure, intermolecular forces of attraction are strongest in a sample of (1) ethanoic acid (3) propanone (2) ethanol (4) water 13) Which substance has the lowest vapor pressure at 75 C? (1) water (2) propanone (3) ethanoic acid (4) ethanol 14) Which liquid has the highest vapor pressure at 75 C? (1) ethanoic acid (2) propanone (3) ethanol (4) water 15) A liquid boils when the vapor pressure of the liquid equals the atmospheric pressure on the surface of the liquid. Using Reference Table H, determine the boiling point of water when the atmospheric pressure is 90. kpa. [1] 5) A sample of ethanoic acid at 100 C has a vapor pressure of 6) What is the vapor pressure of ethanol at 75 C? 7) At what temperature does ethanol have a vapor pressure of 50kPa? 8) At what temperature does ethanoic acid have a vapor pressure of 45kPa? 9) At what temperature does water have a vapor pressure of 110kPa? 10) Find the boiling point of propanone. 11) Find the vapor pressure of ethanol at 75 C. 12) At 50. C and standard pressure, intermolecular forces of attraction are strongest in a sample of (1) ethanoic acid (3) propanone (2) ethanol (4) water 13) Which substance has the lowest vapor pressure at 75 C? (1) water (2) propanone (3) ethanoic acid (4) ethanol 14) Which liquid has the highest vapor pressure at 75 C? (1) ethanoic acid (2) propanone (3) ethanol (4) water 15) A liquid boils when the vapor pressure of the liquid equals the atmospheric pressure on the surface of the liquid. Using Reference Table H, determine the boiling point of water when the atmospheric pressure is 90. kpa. [1]
Name: Pd: Date: HW 11.1 Vapor Pressure (Table H) 10 points SUMMARY OF THE LESSON: [10 points] In a coherent, well-written paragraph Explain, in terms of particle behavior, what vapor pressure is Describe, in terms of vapor pressure and atmospheric pressure, when a substance boils and EXPLAIN WHY. Explain, in terms of vapor pressure, why it is possible to boil a substance at room temperature. Explain, in terms of particle motion, why raising the temperature raises the vapor pressure of the substance. REGENTS PRACTICE: [3 points] 1. The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the pressure on the surface of the liquid. The heat of vaporization of ethanol is 838 joules per gram. A sample of ethanol has a mass of 65.0 grams and is boiling at 1.00 atmosphere. a) Based on Table H, what is the temperature of this sample of ethanol? [1] b) Calculate the minimum amount of heat required to completely vaporize this sample of ethanol. Your response must include both a correct numerical setup and the calculated result. [2]
2. Rubbing alcohol is a product available at most pharmacies and supermarkets. One rubbing alcohol solution contains 2-propanol and water. The boiling point of 2-propanol is 82.3 C at standard pressure. a) Determine the vapor pressure of water at a temperature equal to the boiling point of the 2-propanol. [1] 3. Ethane, C 2H 6, has a boiling point of -89 C at standard pressure. Ethanol, C 2H 5OH, has a much higher boiling point than ethane at standard pressure. At STP, ethane is a gas and ethanol is a liquid. a) Identify the class of organic compounds to which ethanol belongs. [1] b) A liquid boils when the vapor pressure of the liquid equals the atmospheric pressure on the surface of the liquid. Based on Table H, what is the boiling point of ethanol at standard pressure? [1] c) Compare the intermolecular forces of the two substances at STP. [1] Complete any missing assignments!