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Burning Food to Count Its Calories

8th grade nonfiction passage about how food energy is measured: 267 words, seven questions, an answer key and vocabulary.

8th grade nonfiction how food energy is measured 267 words

Burning Food to Count Its Calories

A food label lists calories, but what exactly is being counted? A calorie is a unit of energy. Strictly speaking, the Calorie on a label is the larger unit, the kilocalorie, which equals a thousand small calories. One small calorie is about the energy needed to warm one gram of water by one degree Celsius.

To measure the energy in a food, scientists have long used a device called a bomb calorimeter. A small, dried sample of the food is sealed inside a strong steel chamber filled with oxygen and lit by an electric spark. The chamber sits in a known amount of water. As the food burns, it gives off heat, the water warms, and a thermometer records the rise. Because the amount of water is known, the temperature change reveals how much energy the food released.

This method measures the energy in a food, but the human body is not a furnace. Digestion does not extract every bit of energy, and fiber, for example, passes through mostly undigested. In the late 1800s, an American chemist named Wilbur Atwater studied how much usable energy people actually get from different nutrients. His work led to averages still used today: protein and carbohydrate supply about four Calories per gram, while fat supplies about nine. Labels rely on such averages, so the numbers are close estimates rather than exact measurements.

Calories are only part of nutrition. Two foods with the same count can differ greatly in vitamins, minerals, and fiber. Energy is the fuel, but food also supplies the materials that the body uses to grow and repair itself.

Questions

  1. What is a bomb calorimeter? in the text

  2. What does the thermometer record in a calorimeter? in the text

  3. About how many Calories per gram does fat supply? in the text

  4. Why is the number from burning food not exactly what the body gets? think about it

  5. What did Wilbur Atwater study? in the text

  6. Why are the numbers on food labels only estimates? think about it

  7. What does food supply besides energy? in the text

Words to know

calorie
a unit that measures energy
calorimeter
a device that measures heat by burning something
kilocalorie
a unit of energy equal to one thousand small calories
fiber
plant material in food that the body cannot digest
nutrients
substances in food that the body needs
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 251 words · Flesch-Kincaid grade 5.6

Food labels list calories. But what is being counted? A calorie is a unit of energy. The Calorie on a label is really the larger unit, the kilocalorie. It equals a thousand small calories. One small calorie is about the energy it takes to warm one gram of water by one degree Celsius.

To measure the energy in food, scientists use a device called a bomb calorimeter. They seal a small dried bit of the food in a strong steel chamber. The chamber is full of oxygen. An electric spark lights the food. The chamber sits in a known amount of water. When the food burns, it gives off heat. The water warms up, and a thermometer shows how much. Since the amount of water is known, the change in heat tells how much energy the food gave off.

But the body is not a furnace. Digestion does not get every bit of energy out of food. Fiber, for example, mostly passes through. In the late 1800s, an American chemist named Wilbur Atwater studied how much usable energy people really get from food. His work gave us averages we still use. Protein and carbohydrate give about four Calories per gram. Fat gives about nine. Labels use these averages. So the numbers are close guesses, not exact.

Calories are only part of nutrition. Two foods can have the same count but different vitamins, minerals, and fiber. Food gives energy. It also gives the body what it needs to grow and repair itself.

▲ This passage · 267 words · Flesch-Kincaid grade 9.6

A food label lists calories, but what exactly is being counted? A calorie is a unit of energy. Strictly speaking, the Calorie on a label is the larger unit, the kilocalorie, which equals a thousand small calories. One small calorie is about the energy needed to warm one gram of water by one degree Celsius.

To measure the energy in a food, scientists have long used a device called a bomb calorimeter. A small, dried sample of the food is sealed inside a strong steel chamber filled with oxygen and lit by an electric spark. The chamber sits in a known amount of water. As the food burns, it gives off heat, the water warms, and a thermometer records the rise. Because the amount of water is known, the temperature change reveals how much energy the food released.

This method measures the energy in a food, but the human body is not a furnace. Digestion does not extract every bit of energy, and fiber, for example, passes through mostly undigested. In the late 1800s, an American chemist named Wilbur Atwater studied how much usable energy people actually get from different nutrients. His work led to averages still used today: protein and carbohydrate supply about four Calories per gram, while fat supplies about nine. Labels rely on such averages, so the numbers are close estimates rather than exact measurements.

Calories are only part of nutrition. Two foods with the same count can differ greatly in vitamins, minerals, and fiber. Energy is the fuel, but food also supplies the materials that the body uses to grow and repair itself.

■ Harder · 284 words · Flesch-Kincaid grade 11.9

A food label lists calories, but what precisely is being counted? A calorie is a unit of energy, and strictly speaking, the Calorie printed on a label is the larger unit, the kilocalorie, which is equivalent to a thousand small calories. One small calorie is approximately the energy needed to warm a single gram of water by one degree Celsius.

To determine the energy contained in a food, scientists have long relied on an apparatus called a bomb calorimeter. A small, dried sample of the food is sealed inside a sturdy steel chamber filled with oxygen and ignited by an electric spark, while the chamber rests in a known quantity of water. As the food burns, it releases heat, the water warms, and a thermometer records the increase. Because the amount of water is known, the temperature change reveals how much energy the food released.

This method measures the energy stored in a food, but the human body is not a furnace. Digestion does not extract every last bit of energy, and fiber, for instance, passes through mostly undigested. In the late 1800s, an American chemist named Wilbur Atwater investigated how much usable energy people genuinely obtain from different nutrients. His work produced averages that are still in use today: protein and carbohydrate supply about four Calories per gram, whereas fat supplies about nine. Labels depend on such averages, so the figures they display are close estimates rather than exact measurements.

Calories represent only one part of nutrition. Two foods with an identical count can differ enormously in their vitamins, minerals, and fiber. Energy is the fuel, yet food also provides the raw materials that the body uses to grow and to repair itself.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put calorie, calorimeter, kilocalorie, fiber and nutrients on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 4 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "Burning Food to Count Its Calories"?

It was written for 8th grade. It has 267 words and works out to a Flesch-Kincaid grade level of about 9.6. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are seven. 5 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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