Chapter 11

1. Chapter 11 Heating and Cooling Curves LecturePLUS Timberlake

2. Heating Curve for Water 120 °C steam 100 °C water  steam 50°C liquid water 0 °C ice liquid -10 °C ice Heat added  LecturePLUS Timberlake

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

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

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

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

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

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

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

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

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

12. Solution CS4 Complete using the terms gains or loses • In the cooling coils of a refrigerator, liquid Freon absorbsheat 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

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

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

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

16. Total: Step 2 + Step 3 = 418,000 J + 193,000 J =611,000 J LecturePLUS Timberlake

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

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