Chapter 3 Lecture

Basic ChemistryFourth Edition

Chapter 3 Matter and Energy3.6 Energy and Nutrition

Learning Goal Use the energy values to calculate the kilojoules (kJ) or kilocalories (kcal) in a food.

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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 FuelCarbohydrates Fats Proteins

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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 cal1 Cal = 1 kcal1 Cal = 4184 J

1 Cal = 4.184 kJ

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Energy Food Values

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

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

Energy Food Values

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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.

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Energy Content of Some Foods

On the labels of packagedfoods, the nutrition facts include the total Caloriesand kilojoules, and the grams of carbohydrate, fat, and protein per serving.

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Guide to Calculating Energy from a Food

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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 carbohydrate19 g fat

23 g proteinNeed total kilojoules from hamburger

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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.

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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 + 170 kcal + 90 kcal

= 410 kcal

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Chemistry Link to Health

The amount of energy needed by a human each day depends on age, gender, and physical activity.

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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

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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.

Learning Check

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Solution

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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.

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Solution

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Concept Map, Matter and Energy