Heating Curves

Chapter 6 Energy and States of Matter Heating and Cooling Curves

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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

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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

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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

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Temperature Changes T(1)

beginning temp.1 ∆T(1)

T(f)

final temp of both

T°C ∆T(2)

T(2)

final temp. 2

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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.

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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

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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

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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

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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

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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

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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

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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?

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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

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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

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= 15

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

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+ 193,000 J

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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

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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

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