Heating curves

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Heating curves

  1. 1. Chapter 6 Energy and States of Matter Heating and Cooling Curves LecturePLUS Timberlake 1
  2. 2. Heating Curve for Water 120 °C steam water → steam 100 °C 50°C 0 °C -10 °C liquid water ice→ liquid ice Heat added → LecturePLUS Timberlake 2
  3. 3. Learning Check CS1 A. The flat lines on a heating curve represent 1) a temperature change 2) a constant temperature 3) a change of state B. The sloped lines on a heating curve represent 1) a temperature change 2) a constant temperature 3) a change of state LecturePLUS Timberlake 3
  4. 4. Solution CS1 A. The flat lines on a heating curve represent 2) a constant temperature 3) a change of state B. The sloped lines on a heating curve represent 1) a temperature change LecturePLUS Timberlake 4
  5. 5. Temperature Changes T(1) beginning temp.1 ∆T(1) T(f) final temp of both T°C ∆T(2) T(2) final temp. 2 LecturePLUS Timberlake 5
  6. 6. Cooling Curve Using the heating curve of water as a guide, draw a cooling curve for water beginning with steam at 110°C and ending at -20°C. LecturePLUS Timberlake 6
  7. 7. Learning Check CS2 A. Water condenses at a temperature of 1) 0°C 2) 50°C 3) 100°C B. At a temperature of 0°C, water 1) freezes 2) melts 3) changes to a gas C. When a gas condenses, heat is 1) released 2) absorbed D. Freezing is 1) endothermic 2) exothermic LecturePLUS Timberlake 7
  8. 8. Solution CS2 A. Water condenses at a temperature of 3) 100°C B. At a temperature of 0°C, water 1) freezes 2) melts C. When a gas condenses, heat is 1) released D. Freezing is 2) exothermic LecturePLUS Timberlake 8
  9. 9. Learning Check CS3 Is energy absorbed (1) or released (2) in each of the following: ____A. Ice to liquid water ____B. Water vapor to rain ____C. Water to ice When it rains, the air becomes 1) warmer 2) cooler 3) does not change LecturePLUS Timberlake 9
  10. 10. Solution CS3 Is energy absorbed (1) or released (2) in each of the following: _1__A. Ice to liquid water _2__B. Water vapor to rain _2__C. Water to ice When it rains, the air becomes 1) warmer LecturePLUS Timberlake 10
  11. 11. Learning Check CS4 Complete using the terms gains or loses In the cooling coils of a refrigerator, liquid Freon ___________ heat from the food and changes to a gas Food ___________heat and becomes colder In the back of the refrigerator, Freon _________ heat and condenses back to a liquid LecturePLUS Timberlake 11
  12. 12. Solution CS4 Complete using the terms gains or loses  In the cooling coils of a refrigerator, liquid Freon absorbs heat from the food and changes to a gas  Food loses heat and becomes colder  In the back of the refrigerator, Freon loses heat and condenses back to a liquid LecturePLUS Timberlake 12
  13. 13. Combining Heat Calculations To reduce a fever, an infant is packed in 1250 g of ice. If the ice at 0°C melts and warms to body temperature (37.0°C) how much heat in joules is absorbed? LecturePLUS Timberlake 13
  14. 14. Combining Heat Calculations Step 1: Diagram the change of state 37°C ∆T = 37.0°C - 0°C = 37.0°C 0°C S L LecturePLUS Timberlake 14
  15. 15. Step 2: Calculate the heat to melt ice (fusion) = 1250 g ice x 334 J 1 g ice = 418,000 J Step 3: Calculate the heat to warm the water from 0°C to 37°C = 1250 g x 37.0°C x 4.18 J g °C 193,000 J LecturePLUS Timberlake = 15
  16. 16. Total: Step 2 + Step 3 = 418,000 J = 611,000 J LecturePLUS Timberlake + 193,000 J 16
  17. 17. Learning Check CS8 A. Why do drops of liquid water form on a glass of iced tea ? B. When it snows, the air temperature seems warmer. How can that be? C. How much heat is needed to change 1.00 g of water at 0° to steam at 100°C? 1) 540 cal 2) 640 cal 3) 720 cal LecturePLUS Timberlake 17
  18. 18. Solution CS8 A. Why do drops of liquid water form on a glass of iced tea? Condensation of water in the air that cools B. When it snows, the air temperature seems warmer. How can that be? Condensation is exothermic; heat is released. C. How much heat is needed to change 10.0 g of water at 0° to steam at 100°C? 2) 640 cal LecturePLUS Timberlake 18

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