Chapter 2 Energy and Matter

1. Chapter 2 Energy and Matter 2.4Energy and Nutrition

2. Calorimeters A calorimeter • is used to measure heat transfer • contains a reaction chamber and thermometer in water • indicates the heat lost by a sample • indicates the heat gained by water

3. Energy and Nutrition On food labels, energy is shown as the nutritional Calorie, written with a capital C. In countries other than the United States, energy is shown in kilojoules (kJ). 1 Cal = 1000 calories 1 Cal = 1 kcal 1 Cal = 4184 J 1 Cal = 4.184 kJ

4. Caloric Food Values • The caloric values for foods indicate the number of kJ or kcal (Cal) provided by 1 g of each type of food.

5. Calories in Some Foods

6. Energy Requirements • The amount of energy needed each day depends on age, gender, and level of physical activity. • If food intake exceeds energy use, a person gains weight. • If food intake is less than energy use, a person loses weight.

7. Learning Check A cup of whole milk contains 12 g of carbohydrate, 9.0 g of fat, and 9.0 g of protein. How many kcal (Cal) does a cup of milk contain? (Round to the nearest 10 kcal.) 1) 50 kcal (50 Cal) 2) 80 kcal (80 Cal) 3) 150 kcal (150 Cal)

8. Solution 3) 150 kcal (or Cal) 12 g carbohydrate x 4 kcal/g = 50 kcal + 9.0 g fat x 9 kcal/g = 80 kcal + 5.0 g protein x 4 kcal/g = 20 kcal = 150 kcal