Talk It Over

Have you ever noticed greasy spots on the sides of paper bags containing certain foods? What is fat in foods? How do you know it is there? How can you tell whether some foods contain more fat than others do?

Get

• Several brands of potato chips
• Graph paper, ¼-inch ruled, 1 piece for each brand of chips
• Wax paper
• Rolling pin
• Towel
• Window
• Tape
• Grease pencil

Go

1. Place a potato chip on a piece of graph paper.
2. Place a piece of wax paper over it.
3. Roll with a rolling pin, crushing the chip between the wax paper and the graph paper. Roll long and hard until the chip is thoroughly crushed.
4.  
5. Remove the graph paper. Wipe it with a towel to get rid of little pieces of chip that cling to the paper.
6. Tape the graph paper to a window. Notice that the paper is translucent in some places. (Translucent means that it lets light through. The greasy spot the chip left is translucent.) Record your observations.
7. Count the number of squares on the graph paper that are translucent. Any square that is one-half or more translucent counts as a whole square. Mark the squares with the grease pencil as you go, so that you can keep count.
8. Repeat steps 1 through 6 twice more, using the same brand of chip. This will give you three trials to average.
9. Repeat steps 1–7 for each brand of potato chip you want to test.

Stay Safe

Hang on to that rolling pin—you'll say "Ouch!" if you drop it on your toe. Don't eat the chips you crush. Discard the chip crumbs and the wax paper sheets.

Go Easy

Follow the "Go" procedure, but omit step 7. Count translucent squares for only 1 chip of each brand.

Go Far

Examine the nutrition label on the chip package. Find the approximate number of chips in 1 serving. Find the total number of fat grams per serving.

To find the grams of fat in one chip, divide the fat grams by the number of chips. For example, if one serving is 7 chips and the grams of fat is 10, the grams of fat per chip is 10 ÷ 7 = 1.43. Add the calculated fat value to your data table. This number should be proportional to the number of squares you counted. Is it?

If you want to extend this project, develop your own procedure for measuring the fat in milk, cheese, baked goods, or snack foods.

Show Your Results

For "Go Easy," use a data table like this:

For "Go," your table should look like this:

For "Go Easy" and "Go," make a bar graph that compares numbers of translucent squares (on the vertical axis) by brand (on the horizontal axis). For "Go," use your average from three trials.

For "Go Far," add to the data table a column for the fat grams/chip value you calculated from the nutrition label. When you make your bar graph, set up two vertical axes. Put translucent squares per chip on a vertical axis on the left. Put fat grams per chip on a vertical axis on the right. Use different color bars to show how your measured and calculated values compare. Your graph will look something like this:

For "Go" and "Go Easy," write a few sentences about how the chips compare in their fat content. For "Go Far," add a discussion of how well your measured and calculated values compare. Try to explain why they are alike or different.

Tips and Tricks

When selecting chips to crush, choose unbroken chips of average size. Large, small, or damaged chips will give you imprecise measurements.

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CliffsNotes Parent's Crash Course Elementary School Science Fair Projects
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