1. Energy Measuring Heat Calorimetry
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

2. Heat Equation The heat equation. q = m x c x T
Heat(q) = g x °C x cal = cal
g°C
The amount of heat lost or gained by a substance
is calculated from the
Mass of substance (g).
Temperature change (T).
Specific heat of the substance (cal/g°C).

3. Specific Heat Specific heat Is different for different substances.
Is the amount of heat that raises the temperature of 1 g of a substance by 1°C.
In the SI system has units of J/gC.
In the metric system heat has units of cal/gC.
Water has a specific heat of 1 cal/gC

4. Examples of Specific Heats
Table 3.7
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

5. Using Specific Heat
A layer of copper on a pan has a mass of 135 g. How much heat in calories will raise the temperature of the copper from 26°C to 328°C if the specific heat of copper is cal/g°C?
The temperature change is 328°C - 26°C = 302°C.
heat (cal) = m x T x c(Cu)
135 g x 302°C x cal g°C
= 3,751 cal or 3.75 kcal

6. Learning Check
How many calories (kcal) are needed to raise the temperature of 325 g of water from 15.0°C to 77.0°C?
1) kcal
2) kcal
3) kcal

7. Solution
How many kilocalories are needed to raise the temperature of 325 g of water from 15.5°C to 77.5°C?
1) kcal
77.0°C – 15.0°C = 62.0°C
325 g x 62.0°C x cal x 1 kcal
g °C cal
= kcal

8. Learning Check What is the specific heat of a metal if 24.8 g
absorbs 66 cals of energy and the temperature
rises from 20.2C to 24.5C?

9. Solution What is the specific heat of a metal if 24.8 g absorbs
66 cals of energy and the temperature rises from
20.2C to 24.5C? Equation: q = m c ΔT
Given: 24.8 g, 66 cal, 20.2C to 24.5C Need: cal/gC
Plan: c (specific heat) = Heat/gC
ΔT = 24.5C – 20.2C = 4.3 C
Rearrange Equation: c = heat (q)
(mass)(T)
Set Up: cal = cal/gC
(24.8 g)(4.3C)

10. Calculating Mass
Aluminum is used to make kitchen utensils. What is the mass of an aluminum spatula if 777 cal of heat raise its temperature from 20.0°C to 45.0°C. SHAl = cal/g°C?
Given: 777 cal, 20.0°C to 45.0°C
ΔT = 25.0°C
Plan: Solve heat equation for mass
m = heat
ΔT x SH
Set Up: cal = g Al
25.0°C x 0.22 cal/g°C

11. Transferring Heat Energy
Flows from a warmer object to a colder object.
Provides kinetic energy for the colder object.
Heat lost by the warmer object is equal to the heat energy gained by the colder object.

12. Calorimeters and Heat Transfer
A calorimeter
Is used to measure heat transfer.
Can be made with a coffee cup, water, and a thermometer.
Indicates the heat lost by a sample and gained by water.
Heat lost (-q) = Heat (q) gained
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

13. Measuring Heat Changes
A 50.0-g sample of tin is heated to 99.8°C and dropped into 50.0 g water at 15.6°C. If the final temperature is 19.8°C, what is the specific heat of tin?
Heat gain (q) by water
= 50.0 g x 4.2°C x 1.00 cal/g°C = 210 cal
Heat loss (-q) by tin = -210 cal
SH tin = cal = cal/g°C
(50.0 g)(-80.0°C)

14. Energy and Nutrition
On food labels, energy is shown as the nutritional Calorie, written with a capital C. In countries other than the U.S., energy is shown in kilojoules (kJ).
1 Cal = 1000 cal
1 Cal = 1 kcal
How Calories compare to Joules (another unit of hear):
1 Cal = J
1 Cal = kJ

15. Caloric Food Values The caloric or energy values for 1 g of a food
is given in
kJ or
kcal (Cal)
Table 3.8
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

16. Energy Values for Some Foods
Table 3.9
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

17. Learning Check
A cup of whole milk contains 12 g carbohydrate, 9.0 g fat, and 9.0 g protein. How many kcal (Cal) does a cup of milk contain?
1) 48 kcal (48 Cal)
2) 81 kcal (81 Cal)
3) 165 kcal (165 Cal)

18. Solution 3) 165 kcal 12 g carbohydrate x 4 kcal/g = 48 kcal
9.0 g fat x 9 kcal/g = 81 kcal
9.0 g protein x 4 kcal/g = 36 kcal
Total kcal = kcal
= Cal