Chapter 6
Energy and States of Matter
Measuring Heat Energy
Energy and Nutrition
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Heat
Energy that flows from something warm to
something cooler
A hotter substance gives KE to a cooler
one
When heat is transferred (lost or gained),
there is a change in the energy within the
substance
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Learning Check H1
A. When you touch ice, heat is transferred
from
1) your hand to the ice
2) the ice to your hand
B. When you drink a hot cup of coffee, heat
is transferred from
1) your mouth to the coffee
2) the coffee to your mouth
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Solution H1
A. When you touch ice, heat is transferred
from
1) your hand to the ice
B. When you drink a hot cup of coffee, heat
is transferred from
2) the coffee to your mouth
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Learning Check H2
When you heat 200 g of water for 1 minute, the
water temperature rises from 10°C to 18°C.
400 g
200 g
If you heat 400 g of water at 10°C in the same
pan with the same amount of heat for 1
minute, what would you expect the final
temperature to be?
1) 10 °C
2) 14°C
3) 18°C
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Solution H2
2)14°C
Heating twice the mass of water using the
same amount of heat will raise the
temperature only half as much.
400 g
200 g
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Some Equalities for Heat
Heat is measured in calories or joules
 1 kcal = 1000 cal
 1 calorie = 4.18J
 1 kJ = 1000 J
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Specific Heat
 Why do some foods stay hot longer than
others?
 Why is the beach sand hot, but the water is
cool on the same hot day?
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Specific Heat
Different substances have different
capacities for storing energy
It may take 20 minutes to heat water to
75°C. However, the same mass of
aluminum might require 5 minutes and
the same amount of copper may take
only 2 minutes to reach the same
temperature.
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Specific Heat Values
Specific heat is the amount of heat needed to
raise the temperature of 1 g of a substance by
1°C
cal/g°C
J/g°C
water
1.00
4.18
aluminum
copper
silver
gold
0.22
0.093
0.057
0.031
0.90
0.39
0.24
0.13
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Learning Check H3
A. A substance with a large specific heat
1) heats up quickly
2) heats up slowly
B. When ocean water cools, the surrounding air
1) cools
2) warms 3) stays the same
C. Sand in the desert is hot in the day, and cool
at night. Sand must have a
1) high specific heat
2) low specific heat
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Solution H3
A. A substance with a large specific heat
2) heats up slowly
B. When ocean water cools, the surrounding air
2) warms
C. Sand in the desert is hot in the day, and cool
at night. Sand must have a
2) low specific heat
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Measuring Heat
Requires
 Grams of substance
 Temperature change T
 Specific heat of the substance
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Calculating Heat
mass
x temp. change x
grams x
T
x
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specific heat
Sp. Ht.
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Heat Calculations
A hot-water bottle contains 750 g of water at
65°C. If the water cools to body temperature
(37°C), how many calories of heat could be
transferred to sore muscles?
heat = g
x T
750 g x 28°C
x Sp. Ht. (H2O)
x 1.00 cal
g°C
= 21 000
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Learning Check H4
How many kcal are needed to raise the
temperature of 120 g of water from 15°C
to 75°C?
1) 1.8 kcal
2) 7.2 kcal
3) 9.0 kcal
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Solution H4
How many kcal are needed to raise the
temperature of 120 g of water from 15°C to
75°C?
2) 7.2 kcal
120 g x (75°C - 15°C) x 1.00 cal x 1 kcal
g°C
1000 cal
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Energy and Nutrition
1 Calorie (nutritional) = 1 kcal
1 Cal
= 1000 cal
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Caloric Food Values
Carbohydrate = 4 kcal/g
Fat = 9 kcal/g
Protein = 4 kcal/g
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Foods and Calories
Food
Carbo
Fat
carrots,
1 cup
11
0
1
50
banana
26
0
1
110
0
6
6
80
0
3
20
110
beef (3 oz) 0
5
22
130
egg
chicken
(no skin)
Protein Energy(kcal
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Learning Check H5
1.0 cup of whole milk contains 12 g of
carbohydrate, 9.0 g of fat, and 9.0 g of
protein. How many kcal (Cal) are
obtained?
1) 48 kcal
2) 81 kcal
3) 165 kcal
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Solution H5
3) 165 kcal
12 g carbo x 4 kcal/g
=
48 kcal
9.0 g fat
=
81 kcal
=
36 kcal
=
165 kcal
x 9 kcal/g
9.0 g protein x 4 kcal/g
Total kcal
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