NAME: DATE: AP Chemistry POGIL: Calorimetry Why? On a hot summer day, you may find that the cement next to a swimming pool is unbearably hot to walk across, but the water in the pool is too chilly for a nice swim. When heat is added to a substance, the temperature of that substance increases, but not all substances increase at the same rate. In this POGIL, you will explore how mass, temperature, heat energy, and type of substance are related to temperature changes and phase changes. Phenomenon Transfer of Heat Temperature of Hot Water Bath Part A = Copper Shot and Water Initial Temperature of Copper Shot Initial Temperature of Water Final Temperature of Water and Copper Temperature Change of Copper Temperature Change of Water = C = C Part B = Glass Beads and Water Initial Temperature of Glass Beads Initial Temperature of Water Final Temperature of Water and Glass Temperature Change of Glass Temperature Change of Water = C = C 1. Which substance showed the greatest change in temperature? 2. Which substance showed the least change in temperature? 3. Give a possible explanation for these observations.
Success Criteria Determine the specific heat capacity of a substance. Calculate the heat given off/absorbed by a substance through calorimetry. C a l o r i m e t r y Page 2 MODEL 1 Saucepan versus Stockpot 4. Which container holds more water? 5. Refer to the heating instructions for the following: a. How many joules of energy were added to the saucepan? b. How many joules of energy were added to the stockpot? c. Which container gained more energy? d. Which container would show the greater temperature change? Why?
MODEL 2 Experimental Data for Heating Water Experiment 1 Trial Mass (g) ΔT ( C) Energy Added (J) A 1.00 26.8 112 B 2.00 13.4 112 C 3.00 10.7 112 D 4.00 8.93 112 E 5.00 7.66 112 C a l o r i m e t r y Page 3 Experiment 2 Trial Mass (g) ΔT ( C) Energy Added (J) A 3.00 3.00 37.6 B 3.00 6.00 75.2 C 3.00 9.00 113 D 3.00 12.0 150 E 3.00 15.0 188 Experiment 3 Trial Mass (g) ΔT ( C) Energy Added (J) A 1.00 9.00 37.6 B 2.00 9.00 75.0 C 2.50 9.00 94.1 D 3.00 9.00 113 E 3.50 9.00 132 6. What does ΔT mean? 7. Which experiment tests how the amount of energy needed to achieve the same temperature change depends on mass of water? 8. Which experiment tests how different amounts of energy result in different temperature changes when the mass of water is constant? 9. Why is it necessary to perform three experiments to find the relationships between mass, temperature change, and energy? 10. Referring to Experiment 1, when the same amount of energy is added to water samples of different mass, the change in temperature (increases / decreases) as the mass of increases. This relationship is (direct / inverse). 11. Referring to Experiment 2, when energy is added to water samples of same mass, the change in temperature (increases / decreases) as the amount of energy increases. This relationship is (direct / inverse).
C a l o r i m e t r y Page 4 12. Referring to Experiment 3, when the same temperature change is obtained from water samples of different mass, the amount of energy needed (increases / decreases) as the mass of increases. This relationship is (direct / inverse). 13. Circle the proportionality statements that properly show the relationships in Experiments 1-3. Label each proportionality with the Experiment it represents. (q = Energy; m = mass; T = temperature) a. q m or q b. q ΔT or q c. ΔT m or ΔT 1 m 1 ΔT 1 m Experiment # Experiment # Experiment # 14. Based on your answers to #13, write a single proportionality statement for q: q 15. The proportionality statement can be rewritten as an equation if we include a constant, C. Complete the equation to include m and ΔT. q = C 16. Solve the equation in #15 for C. Use one of your experiments from the model to solve for C. Careful with your units. 17. The constant in #16 is called specific heat (C s ). What do the units for specific heat mean? 18. Using your equation and specific heat for water, determine the energy required to increase the temperature 555 grams of water by 20.0 C. MODEL 3 Mercury versus Water Trial Substance Mass (g) ΔT ( C) Energy Added (J) 1 Mercury (Hg) 100.0 71.0 1,000.0 2 Mercury (Hg) 100.0 142 2,000.0 3 Water (H 2 O) 100.0 2.39 1,000.0 4 Water (H 2 O) 100.0 4.78 2,000.0 19. What is the specific heat of mercury?
C a l o r i m e t r y Page 5 20. When adding the same amount of heat energy to two substances of the same mass, the substance with the larger specific heat will have a (larger / smaller) change in temperature. 21. If 23,000 J of energy are used to heat water by 4.00 C, what is the mass of the water? 22. If 23,000 J of energy are used to heat mercury by 4.00 C, what is the mass of the mercury? 23. What is the specific heat of aluminum if 4,750 J of heat energy added to 249 g of aluminum produces a recorded temperature change of 21.1 C? Model 4 Phase Changes 24. Which state of matter requires the most amount of system energy? 25. What process is happening at each of the following? T = U = W = X = Y = Z = 26. Explain why at room temperature CO 2 exists as a gas, but H 2 O exists as a liquid. If they are at the same temperature, they should have the same energy.
Heating Curves C a l o r i m e t r y Page 6 27. What temperature is the ice before heat is applied? 28. Approximately how much heat is added to raise the temperature of the ice to melting point? 29. How much heat is added to melt the ice? 30. How much heat is added to raise the temperature of the water from 0 C to 100 C? 31. How much heat is required to vaporize the water? 32. Compare the amount of energy required to melt the ice to the amount of energy required to vaporize the water. Explain any discrepancy. 33. How much heat would have to be lost for steam to condense back to liquid water? Explain your answer. 34. Calculate the ΔT for the vaporizing of water. What would be the q value if you use q = m C s ΔT?
Model 5: Enthalpies of Change (Energy is Need to Change Phase) C a l o r i m e t r y Page 7 Enthalpies of Change for Water ΔH fus = 333.5 J/g ΔH solid = -333.5 J/g ΔH vap = 2257 J/g ΔH cond = -2257 J/g 35. How does the heat of fusion, ΔH fus, or melting compare to the heat of solidification, ΔH solid, or freezing? Explain their relationship. 36. What is the relationship between the heat of vaporization and heat of condensation? 37. What are the units for enthalpies of change? How do they compare to specific heat, C s? Model 6: Calculating Thermal Energy for Phase Changes q = m ΔH 38. How does this equation compare to the calculation for thermal energy when a substance is in a phase, such as ice or liquid water? 39. Referencing Model 2, calculate the amount of heat required to vaporize 100.0 g of water. 40. What would be the thermal energy for 50.0 g of steam to condense? Is this endothermic or exothermic?
Temperature ( C) C a l o r i m e t r y Page 8 Model 7: Putting it all Together A cube of ice with a mass of 10.0 g and temperature of -50 C is heated on a stove until it becomes steam at 150 C. How much thermal energy was required to accomplish this? 200 150 100 50 0-50 -100 Heating Curve for Water Heat (J) Ice Melt/Freeze Water Vap/ Cond Steam C s(ice) = 2.03 J/g C ΔH fus = 333.5 J/g C s(water) = 4.18 J/g C ΔH vap = 2257 J/g C s(steam) = 2.01 J/g C q ice = m ΔT C s(ice) = 10.0g [0 C (-50 C)] 2.03 J/g C = 1,020 J q melt = m ΔH fus = 10.0g 333.5 J/g = 3,340 J q water = m ΔT C s(water) = 10.0g [100 C 0 C] 4.18 J/g C = 4,180 J q vap = m ΔH vap = 10.0g 2257 J/g = 22,600 J q steam = m ΔT C s(steam) = 10.0g [150 C 100 C] 2.01 J/g C = 1,010 J 41. What do the X s, dots, and arrows represent? 42. Why does it require five separate equations to solve for the thermal energy in the problem? 43. Why is the ΔT for ice written as [0 C (-50 C)] and not [-50 C - 0 C]? 44. What is the one thing that remains the same for each calculation? 45. Does it take more energy to heat water or ice? Explain your answer, but be careful. The water from the problem underwent a 100 C temperature change, but ice only increased by 50 C.