1. Energy and States of Matter Heating and Cooling Curves

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 

3. Reading a Heating Curve 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

4. Solution 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

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

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.

7. Heating and Cooling A. Water condenses at a temperature of 1)0°C2) 50°C3) 100°C B. At a temperature of 0°C, water 1) freezes2) melts3) changes to a gas C. When a gas condenses, heat is 1) released2) absorbed D. Freezing is 1) endothermic2) exothermic

8. Solution A. Water condenses at a temperature of 3) 100°C B. At a temperature of 0°C, water 1) freezes2) melts C. When a gas condenses, heat is 1) released D. Freezing is 2) exothermic

9. Is it Exothermic or Endothermic? 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) warmer2) cooler3) does not change

10. Solution 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

11. Exothermic or Endothermic? 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

12. Solution 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

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?

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

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

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

17. Understanding Heat 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 cal2) 640 cal 3) 720 cal

18. Solution 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