1. Chapter 3 Matter and Energy
3.6 Energy and Nutrition
Learning Goal Use the energy values to calculate the kilojoules (kJ) or kilocalories (kcal) in a food.
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2. Carbohydrates Fats Proteins
Energy and Nutrition
Carbohydrates are the body’s primary source of energy; however, when carbohydrate reserves are exhausted, fats and then proteins are used for energy.
Primary Fuel
Carbohydrates Fats Proteins
© 2014 Pearson Education, Inc.

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 cal
1 Cal = 1 kcal
1 Cal = 4184 J
1 Cal = kJ

4. Energy Food Values
Foods are burned in a calorimeter to determine their energy values (kJ/g or kcal/g).

5. Energy Food Values
Energy values for the three food types are in kJ/g and kcal/g.

6. Energy Food Values
We can use energy values in Table 3.9 to calculate the energy from a food type when its mass is known.

7. Energy Content of Some Foods
On the labels of packaged
foods, the nutrition facts
include the total Calories
and kilojoules, and the
grams of carbohydrate,
fat, and protein per
serving.

8. Guide to Calculating Energy from a Food

9. Sample Problem, Energy from a Food
A hamburger sandwich contains 37 g of carbohydrate, 19 g of fat, and 23 g of protein. What is the total energy (kcal) from this food?
Step 1 Given 37 g carbohydrate
19 g fat
23 g protein
Need total kilojoules from hamburger

10. Sample Problem, Energy from a Food
A hamburger sandwich contains 37 g of carbohydrate, 19 g of fat, and 23 g of protein. What is the total energy (kcal) from this food?
Step 2 Use the energy value for each food type and calculate.

11. Sample Problem, Energy from a Food
A hamburger sandwich contains 37 g of carbohydrate, 19 g of fat, and 23 g of protein. What is the total energy (kcal) from this food?
Step 3 Add the energy from each food
type to get total energy.
Total energy = 150 kcal kcal kcal
= 410 kcal

12. Chemistry Link to Health
The amount of energy needed by a human each day depends on age, gender, and physical activity.

13. Chemistry Link to Health
A person loses weight when his or her intake of calories is less than the calories used in a given day.
Kilocalories burned per hour of
walking are 200
swimming are 500
running are 750

14. Learning Check
Using the energy values per food type in Table 3.9, calculate the total energy (kcal) obtained from a diet that includes 52 g of carbohydrates, 6 g of fat, and 130 g protein.

15. Solution
Using the energy values per food type in Table 3.9, calculate the total energy (kcal) obtained from a diet that includes 52 g of carbohydrates, 6 g of fat, and 130 g protein.
Step 1 Given 52 g carbohydrate
6 g fat
130 g protein
Need total energy (kcal)

16. Solution
Calculate the total energy (kcal) obtained from a diet that includes 52 g of carbohydrates, 6 g of fat, and 130 g protein.
Step 2 Use the energy value for each food type and calculate.

17. Solution
Calculate the total energy (kcal) obtained from a diet that includes 52 g of carbohydrates, 6 g of fat and 130 g protein.
Step 3 Add the energy from each food type to calculate the total energy (kcal).
Total energy value
= 210 kcal + 50 kcal kcal
= 770 kcal

18. Concept Map, Matter and Energy