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Chapter 2 Energy and Matter

2.2 Energy and

Nutrition

Copyright © 2009 by Pearson Education, Inc.

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Calorimeters

A calorimeter

• is used to measure heat transfer.

• can be made with a coffee cup and a thermometer.

• indicates the heat lost by a sample

• indicates the heat gained by water.

Copyright © 2009 by Pearson Education, Inc.

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Energy and Nutrition

On food labels, energy is shown as the nutritionalCalorie, written with a capital C. In countries other than the U.S., energy is shown in kilojoules (kJ).

1 Cal = 1000 calories1 Cal = 1 kcal1 Cal = 1000 cal1 Cal = 4184 J

1 Cal = 4.184 kJ

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Caloric Food Values

The caloric or energy values for foods indicate thenumber of kcal (Cal) provided by 1 g of each type of food.

Carbohydrate: 4 kcal 1 g

Fat (lipid): 9 kcal 1 g

Protein: 4 kcal 1 g

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Energy Values for Some Foods

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Energy Requirements

• The amount of energy needed each day depends on age, sex, and physical activity.

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A cup of whole milk contains 12 g of carbohydrate, 9 g of fat, and 5 g of protein. How many kcal (Cal) does a cup of milk contain (round answer to the tens place)?

1) 50 kcal (or Cal)2) 80 kcal (or Cal)3) 150 kcal (or Cal)

Learning Check

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A cup of whole milk contains 12 g of carbohydrate, 9 g of fat, and 5 g of protein. How many kcal (Cal) does a cup of milk contain?

3) 150 kcal (or Cal)

12 g carbohydrates x 4 kcal/g = 50 kcal9 g fat x 9 kcal/g = 80 kcal5 g protein x 4 kcal/g = 20 kcal

150 kcal

Solution

Skim Milk

Note the significance of fat (lipids) in the milk. It represents half of the calories of whole milk. Remove the fat, and the calorie content drops by 80 kcal.

However, skim milk is not for everyone. Children require the lipids in the milk for growth. Adults, especially those who struggle with weight, can dispense with the fats. Among animals, the fat content in a mother’s milk can be very high – such as among bears, seals, and whales.