Potato Chip Science: How Greasy Are Your Potato Chips?
Potato chip science is big business! The FDA (Food and Drug Administration) does some very important tests so that the food you eat—including potato chips—is accurately labeled. We may not have access to the FDA’s expensive machines, but we can still do some pretty cool tests without them.
For this science fair project, let’s assume you’re a scientist working for the FDA and that you need to double-check the fat content (or “greasiness”) of several brands of potato chips. If you don’t have any specialized machines, then how do you find out how much grease your chips have?
One thing we could try is to simply mash up a potato chip and look at how much grease comes out. Paper absorbs grease really well, so we can use it as our “instrument” to help us quantify—or find a number that describes—how much grease is in an individual chip.
But wait a minute. Not all potato chips are the same size! Even chips from the same bag come in different sizes, and of course, different brands usually make differently sized chips. If we were to test a really big chip, we would get more grease than if we tested a small one, and this certainly wouldn’t describe how much grease is in a single serving of chips very well. So what’s a good way to determine how much grease is in your potato chips?
We can calculate a useful number known as an average to describe how much grease we have in our chips. We can find the average by adding together all of the grease we find divided by the number of chips we used to get that much grease.
How greasy are different brands of potato chips?
- Several bags of potato chips (different brands)
- Something to write with
- Rolling Pin
- Wax Paper, plastic wrap, or large sandwich bag
- Graph paper
- Find the serving size listed in the nutrition facts for each brand of chips.
- Write down the serving size for each brand. If we’re trying to determine if a serving of one brand of chips is greasier than another, why do you think recording the serving size for each brand of chip is important?
- Find the total fat per serving for each brand of chips, in grams. Record this number.
- Pick a brand of chips. Count out a number of chips equal to the serving size for that brand. Make sure to pull chips randomly from the bag. Don’t pick big or small ones, specifically. If we want to take an accurate average, why do you think this is important?
- Place the chips on a sheet of graph paper. Record the amount of chips you pulled out for this brand of chips.
- Lay the wax paper, plastic wrap, or large sandwich bag over the chips.
- Use this time to formulate your hypothesis. Which brand of chips do you think will be the greasiest?
- Roll over the chips several times with the rolling pin, making sure they’re totally pulverized.
- Remove the graph paper and throw away the chips. Tape the graph paper to a window (or the surface of your school’s overhead projector, if you have access to one).
- Count the number of squares that are translucent from the grease. (Hint: make a check mark in each square you’re counting. You can use a pencil, pen, or grease pencil if you’re marking the graph paper itself. If you’re using an overhead projector, you can use a dry-erase marker to mark squares projected onto the whiteboard.) Only count squares that are ½ full or more. Record the number of squares you count for this brand.
- Repeat steps 4-10 for each brand.
- The average grease per serving size is simply the amount of squares you counted for each brand. To calculate the average grease per chip, divide squares counted by the number of chips tested. Record this number for all brands in your data chart.
- Draw a graph like the one below comparing the listed fat value per serving for each brand of chips and the number of squares you counted when you did the experiment. Does the data surprise you, or is it what you expected? What does it suggest about the accuracy of your measurements?