Name: REGENTS CHEMISTRY

Transcription

1 Name: REGENTS CHEMISTRY 1

2 Key Ideas Matter is classified as a pure substance or as a mixture of substances. (3.1q) Mixtures are composed of two or more different substances that can be separated by physical means. When different substances are mixed together, a homogeneous or heterogeneous mixture is formed.(3.1s) The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties. (3.1t) The three phases of matter (solids, liquids, and gases)have different properties.(3.1kk) Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the mixture. (3.1nn) Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. (4.2a) Temperature is a measurement of the average kinetic energy of the particles in a sample of material. Temperature is not a form of energy. (4.2b) The concepts of potential and kinetic energy can be used to explain physical processes that include: fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and deposition. (4.2c) Section 1: Phases Fill in the blank with a vocabulary word to determine the key ideas: The three phases of matter (,, and ) have different properties. Heat is a transfer of (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. Temperature is a measurement of the average of the particles in a sample of material. Temperature is not a form of energy. The concepts of kinetic and potential energy can be used to explain physical processes that include: fusion (melting), solidification ( ), vaporization (boiling, ), condensation, sublimation, and deposition. Chemical and changes can be exothermic or endothermic. The structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure. 2

3 Which phase of matter has definite shape and volume? Which phase of matter is easily compressible? What type of energy is defined as stored energy? What type of energy(s) directly related to the temperature of a sample? Draw representations of the following: Solid Liquid Gas Classifying Matter Fill in the blank with a vocabulary word to determine the key ideas: Matter is classified as a pure substance or as a of substances. A pure (element or compound) has a constant composition and constant properties throughout a given sample, and from sample to sample. cannot be broken down by chemical change. Mixtures are composed of two or more different substances that can be separated by physical means. When different substances are mixed together, a or heterogeneous mixture is formed. The proportions of components in a can be varied. Each component in a mixture retains its original properties. Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the. A is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent. 3

4 Vapor Pressure Liquids evaporate when they are left in the open air. This is also known as. Liquids also go through this phase changed in closed containers. The vapor that is produced in either container exerts a pressure on top of the liquid phase. This pressure is known as. In order for the vapor to escape its original liquid phase completely its pressure must overcome the regular atmospheric pressure above it. As temperature of the liquid increases, the number of particles evaporating and the vapor pressure. Therefore, temperature and vapor pressure have a direct correlation. Under high atmospheric pressure, the liquid will have a harder time escaping the liquid phase so the temperature at which it boils is higher than normal. Under low atmospheric pressure, the liquid will have an easier time escaping the liquid phase so the temperature at which it boils is than normal. Use Table H to answer these questions: 1. Which substance has the lowest boiling point? 2. Which substance has a normal boiling point of 100C? 3. What is the normal boiling point of propanone? 4. Which substance has the highest vapor pressure at 40C? 5. At what pressure will water boil at 90C? 6. What temperature will ethanoic acid boil at 48kPa? 7. What temperature will water boil at 110kPa? 8. When the vapor pressure reaches atmospheric pressure the liquid will undergo what phase change? 9. We live at sea level which has a normal pressure of 1 atmosphere, or kpa. Since we live at normal pressure, our water boils at the normal boiling point for water: C. 4

5 10. Find the vapor pressure using Table H: a. Propanone at 25 C:, 50 C:, 75 C:. b. Water at 85 C:, 100 C:, 110 C:. c. Ethanoic acid at 95 C:, 100 C:, 120 C:. 11. Give the boiling point using Table H: a. Propane at 30kPa:, 50kPa:, 75kPa:. b. Ethanol at 25kPa:, 65kPa:, 95 kpa:. c. Water at 15kPa:, 70kPa:, 105 kpa:. 12. What is the trend shown in table H for vapor pressure versus boiling point? 13. Explain the trend in terms of particles of the gas and liquid phases. 14. Which of the substances on table H has the weakest IMF? 15. Which of the substances on table H has the strongest IMF? Section 2: Heat Heat is a transfer of energy (usually thermal energy) from a body of temperature to a body of temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. Temperature is a measurement of the average of the particles in a sample of material. Temperature is not a form of energy. The concepts of potential and kinetic energy can be used to explain physical processes that include: fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and. Exothermic reactions heat and have values. Endothermic reactions heat and have values. 1. Write the equation for the reaction on Table I that becomes the least stable: 2. What type of reaction (endo or exo) is the dissolving of LiBr? 5

6 3. If 3 moles of C 3 H 8 burn in oxygen, how many kilojoules of heat are released? (show work) Heat Table I 1. Are the following endo or exothermic? CH 4 + 2O 2 à CO 2 + 2H 2 O 2CH 3 OH + 3O 2 à 2CO 2 + 4H 2 O kJ H 2 + I 2 à 2HI The dissolving of NaOH 25.69kJ + NH 4 NO 3 à NH NO 3 The dissolving of LiBr 2. Circle the more stable compound in each pair: H 2 O (g) OR H 2 O (l) NH 3 OR Al 2 O 3 HI OR NO C 2 H 6 OR C 2 H 4 3. Circle the compound which is more likely to form in each pair: CO 2 from elements OR CO 2 from CO NO OR NO 2 C 2 H 6 OR C 2 H 2 NH 3 OR HI 4. Will the following feel hot or cold? Dissolving KNO 3 Dissolving LiBr Burning CH 4 in O 2 Forming Al 2 O 3 5. Write a balanced equation for the following reactions including the heat as a reactant or product: The formation of H 2 O from its elements The decomposition of C 2 H 6 The dissolving of NH 4 Cl The evaporation of water from Li + and Br - 6

7 Specific Heat Specific heat is defined as the amount of heat (in ) needed to raise gram of a substance C. Every substance has its own specific heat depending on the bonds and forces it has. 1. When you wake up in the morning and touch the floor, at first the carpet feels warm. The wood floor in the hallway is a bit chilly, but the tile floor in the bathroom is FREEZING! However, your whole house is probably 68 F. What quality is different about each of these surfaces? Which has the highest specific heat? 2. At the park, why do you tend to steer clear of metal benches and prefer wooden picnic benches? Which has a lower specific heat? 3. Water has a high specific heat due to its hydrogen bonds. Explain why the fish is so happy in the picture below. 4. Based on the specific heat values in the table below, why do Al, Cu, Au, Fe and Hg have very low values? (What do they have in common?) 5. Based on your answer to question 2 do you expect wood to have a higher or lower specific heat than these substances and why? 6. Glass is often called an insulator because it has a specific heat. 7

8 Section 3: Heat Calculations Define the following terms with units: q: c: m: ΔT: Answer the following questions using the heat formula. Show work with units and significant figures. 1. How many Joules of energy are needed to change the temperature of grams of water from 20.0C to 40.0C? 2. How many kilojoules of energy are needed to change the temperature of 15.0 grams of water from 35.0C to 75.0C? 3. If the temperature of water is changed from 10.0C to 35.0C by the addition of 350.0J, how many grams were heated? 4. If the temperature of water is changed from 100.0C to 250.0C by the addition of J, how many grams were heated? 5. If J of energy are applied to grams of water at 50.0C, what is the final temperature? 6. If 425J of energy are released from 25.0 grams of water at 25.0C, what is the final temperature? 7. Look at the rearranged equation for heat, solved for specific heat. What are the units of specific heat based on this rearranged equation? 8. What is the specific heat of silver if an 80.0 gram sample is heated from 24.0C to 49.0C by adding 468.2J? 9. What is the specific heat of copper if a 75.0 gram sample of copper is heated from 20.0C to 24.0C by adding 117J? 10. The specific heat of aluminum is 0.88J/gC. How many joules of heat does it take to heat 50.0 grams of aluminum from 20.0 to 70.0C? 8

9 11. What is the change in temperature when 3.00 grams of Iron (specific heat = 0.45J/gC) is subjected to J of energy? 12. What mass of Aluminum (specific heat = J/gC) can be heated from 25.0C to 90.0C with the addition of 100.0J of heat? 13. How many joules of heat must be released in order to change the temperature of 50.0 grams of air (specific heat 1.01 J/gC) from 35.0C to 25.0C? Base answers to questions on the diagram: 14. How much heat is added to change the substance from the coldest to the warmest pure liquid state? 15. If the specific heat of this substances in the liquid phase is 3.56 J/gC calculate how many grams were heated in question 11? 16. If the same sample is heated as a solid at 40C to 60C will it have the same specific heat? Show work to support your answer. 17. How much heat will need to be added to the same sample in order to raise the temperature from 20.0C to 40.0C? (Notice this is not on the graph, you must calculate it based on your answers above.) 9

10 Section 4: Heating and Cooling Curves 1. Label the line segments with their phase(s). 2. What is this substance s melting point? 3. What is this substance s boiling point? 4. Does this represent an endothermic or exothermic reaction? 5. Heat is being released at 60.0 kilojoules per minute. How much heat is released when the substance freezes? 6. Label the point with the most kinetic energy with a star. 7. Draw six particles of this substance as it looks for the first line segment in the box below. 8. Draw six particles of this substance as it looks for the last line segment in the box below. 9. At which point is the potential energy the highest? Label it with a star. 10. What is the boiling point of this substance? 11. What is the melting point of this substance? 12. What would you expect the graph to do if the substance continued to be heated? 10

11 Section 5: Heat of Vaporization and Fusion Heat of Fusion of water: Heat of Vaporization of water: Specific Heat of gaseous water: Specific Heat of liquid water: Specific Heat of solid water: 334 J/g 2260 J/g 1.84 J/gC 4.18 J/gC 2.09 J/gC Show all work and answers with three significant figures and proper units. Write the formula(s) you used first then show your work. 1. How many Joules of heat are required to change the temperature of grams of solid water from C to 0.0C? 2. How many Joules of heat are needed to change grams of water from solid to liquid? 3. How many Joules of heat are required to change the temperature of grams of liquid water from 0.0C to 100.0C? 4. How many Joules of heat are needed to change grams of water from liquid to gas? 5. How many Joules of heat are required to change the temperature of grams of gaseous water from 100.0C to 120.0C? 6. How many Joules of heat are required to change the temperature of grams of solid water from C to 0.0C and then melt it? 7. How is your answer to question 6 related to your answers to questions 1 and 2? 8. Using the rule you obtained in question 7 and your answers to questions 1-5, how much heat is required to heat grams of water from to 120.0C? 11

12 9. Draw a heating curve to show the phase changes that occurred during the processes described in questions 1-5. Label each segment with the phase(s) on the top of the line and the formula you used to determine the amount of heat added on the bottom of the line. Keep in mind the x axis should be the TOTAL heat used in the reaction and the y axis should be temperature in degrees Celsius. Additional Questions: 10. How much heat is absorbed by 550.0g block of ice to raise the temperature from to 0.0C? 11. How much heat is needed to vaporize grams of water? 12. How much heat is released when 25.0 grams of water freezes? 13. Calculate the heat needed to change 50.0 grams of liquid water to gas at 100.0C. 14. Calculate the heat released when 125 grams of liquid water solidifies. 15. How much heat energy must be absorbed to raise the temperature of a gram block of ice from to 0.0C and then completely melt it to a liquid at the same temperature? 12

13 16. How much energy would be required to heat the same grams of liquid water in #15 (at 0.0C) to the normal boiling point of water and then vaporize it? 17. If the temperature of the grams of steam generated in #12 were heated to a new temperature of 120.0C, how much energy would be absorbed? 18. What is the total amount of energy needed to heat grams of ice at - 10C to gas at 120.0C? 19. What is the total amount of energy needed to heat 125g of ice at - 25C to gas at 135.0C? (Use a heating curve to help you). 20. The heat of vaporization of substance X is 250.0J/g. How much heat is needed to change 10.0 grams of X from liquid to gas? 21. The heat of fusion of substance Y is 125 J/g. How much heat is needed to change 25.0 grams of Y from solid to liquid? 22. The heat of sublimation of substance XY 2 is J/g. calculate the heat required to sublime grams of XY Hypothesize a possible heat of sublimation for water and give your reasoning. 13

14 Multiple Choice Review 1. At 298 K, the vapor pressure of H 2 O is less than the vapor pressure of CH 3 OH because H 2 O has A) larger molecules B) a larger molecular mass C) stronger ionic bonds D) stronger hydrogen bonds 2. At 50. C and standard pressure, intermolecular forces of attraction are strongest in a sample of A) ethanoic acid B) ethanol C) propanone D) water 3. At which temperature is the vapor pressure of ethanol equal to 80. kpa? A) 48C B) 73C C) 80C D) 101C 4. Which liquid has the lowest vapor pressure at 65 C? A) ethanoic acid B) ethanol C) propanone D) water 5. Which liquid has the highest vapor pressure at 75 C? A) ethanoic acid B) ethanol C) propanone D) water 6. As the temperature of a liquid increases, its vapor pressure A) Decreases B) increases C) remains the same 7. The graph below represents the vapor curves of four liquids. (Standard pressure is 760mmHg) Which liquid has the highest normal boiling point? A) A B) B C) C D) D 8. Which sample of water will have the highest vapor pressure? A) 10.0 ml at 62 C B) 20.0 ml at 52 C C) 30.0 ml at 42 C D) 40.0 ml at 32 C 9. Which statement best describes the shape and volume of an aluminum cylinder at STP? A) It has a definite shape and a definite volume. B) It has a definite shape and no definite volume. C) It has no definite shape and a definite volume. D) It has no definite shape and no definite volume. 14

15 10. Which grouping of the three phases of bromine is listed in order from left to right for increasing distance between bromine molecules? A) gas, liquid, solid C) liquid, solid, gas B) solid, gas, liquid D) solid, liquid, gas 11. Which 5.0- milliliter sample of NH3 will take the shape of and completely fill a closed milliliter container? A) NH3(s) B) NH3(g) C) NH3(aq) 12. Which phase change results in the release of energy? A) H2O(s) à H2O(l) B) H2O(s)à H2O(g) C) H2O(s) à H2O(g) D) H2O(g) à H2O(l) 13. Which kind of energy is stored within a chemical substance? A) free energy C) activation energy B) kinetic energy D) potential energy 14. At which temperature would atoms of a He(g) sample have the greatest average kinetic energy? A) 25 C B) 37 C C) 273 K D) 298 K 15. Solid A at 80ºC is immersed in liquid B at 60ºC. Which statement correctly describes the energy changes between A and B? A) A releases heat and B absorbs heat. B) A absorbs heat and B releases heat. C) Both A and B absorb heat. D) Both A and B release heat. 16. Which change of phase is exothermic? A) solid to liquid C) gas to liquid B) solid to gas D) liquid to gas 17. The table below shows the data collected by a student as heat was applied at a constant rate to a solid below its freezing point. What is the boiling point of this substance? A) 32 C B) 54 C C) 62 C D) 100 C 15

16 18. The diagram below represents the uniform heating of a substance that is a solid at Time A. Between which times could the heat of fusion be determined? A) A and B C) B and C B) C and D D) E and F 19. A 36- gram sample of water has an initial temperature of 22 C. After the sample absorbs 1200 joules of heat energy, the final temperature of the sample is A) 8.0 C B) 14 C C) 30. C D) 55 C 20. The temperature of a sample of water changes from 10 C to 20 C when the sample absorbs 418 joules of heat. What is the mass of the sample? A) 1 g B) 10 g C) 100 g D) 1000 g 21. When 200 grams of water cools from 50. C to 25 C, the total amount of heat energy released by the water is A) 42 kj B) 21 kj C) 34 J D) 17 J 22. When a 500. gram sample of water at 19.0ºC absorbs 8.40 kilojoules of heat, the temperature of the water will change to A) 23.0ºC B) 19.0ºC C) 15.0ºC D) 4.00ºC 23. The number of Joules needed to raise the temperature of 10 grams of water from 20ºC to 30ºC A) 42 B) 84 C) 420 D) At which Celsius temperature does lead change from a solid to a liquid? A) 874 C B) 601 C C) 328 C D) 0 C 25. What amount of heat is required to completely melt a gram sample of H2O(s) at 0 C? A) 334 J C) 2260 J B) J D) J 16

17 Base your answers to questions 26 and 27 on the graph below. The graph shows heat being added at a constant rate to substance A and to substance B, which begin as solids below their melting point temperatures. 26. During which interval is the greatest amount of energy absorbed? A) 1-2 B) 2-3 C) 3-4 D) Compared to substance B, substance A has a A) lower melting point and a lower boiling point B) lower melting point and a higher boiling point C) higher melting point and a lower boiling point D) higher melting point and a higher boiling point 28. In which process does a solid change directly into a vapor? A) condensation C) sublimation B) deposition D) solidification Base your answers to questions 29 through 32 on the information below. The temperature of a sample of a substance is increased from 20. C to 160. C as the sample absorbs heat at a constant rate of 15 kilojoules per minute at standard pressure. The graph below represents the relationship between temperature and time as the sample is heated. 29. Determine the total amount of heat required to completely melt this sample at its melting point. 30. What is the total time this sample is in the liquid phase, only? 17

18 31. Use the key below to draw at least nine particles in the box, showing the correct particle arrangement of this sample during the first minute of heating. 32. What is the boiling point of this sample? 33. Base your answer to the following question on the information below A gram sample of liquid ammonia is originally at 210. K. The diagram of the partial heating curve below represents the vaporization of the sample of ammonia at standard pressure due to the addition of heat. The heat is not added at a constant rate. Calculate the total heat absorbed by the gram sample of ammonia during time interval AB. Your response must include both a correct numerical setup and the calculated result. 18