Have you ever bitten into an apple and discovered that it is mealy? Yuck! So how can we find out if an apple is mealy before we sample it?
One suggestion was a “thump test.” Have you ever thumped a watermelon to determine if it is ripe enough? Apparently, you can do the same with apples. Let’s try it!
We could compare this test with density and see which is best. First, what is density? It is how tightly packed are the molecules of a substance. As an apple ages, its cells lose water and some of the “glue” that holds the cells together, resulting in a mealy apple.
MATERIALS:
- 5 apples of the same type. If you can get them from an orchard so that you know when they were picked, it would be great. Otherwise, get 5 of the same type from the store. We can assume they’re about the same age.
- Stickers or masking tape to label the apples
- Large measuring cup with milliliter calibrations; it needs to be deep enough so that water will completely cover an apple when placed in the cup.
- Balance or kitchen scale to find the mass of the apple.
- Paper bags to store individual apples.
PROCEDURE:
- Label each apple with a sticker or masking tape, and number them 1 through 5. Each apple should be stored in a paper bag between observations.
Create a table and describe the physical appearance of each apple.
- Find the mass of each apple. Grams are the preferred unit, but use ounces if grams are not available.
- Find the volume of each apple by water displacement. Fill the measuring cup with enough water to cover the apple when pushed to the bottom of the cup. Record how much water is in the cup. Then add the apple and record how much water is in the cup now. Subtract the original water reading from the Water + apple reading. This gives you the volume of your apple.
- Next is the hard part. You must do math (or have an adult help you with this). Density = mass/volume, so divide the mass of your apple by its volume. Your unit should be grams/milliliter or ounces/milliliter. Find the density of all five apples, and record your results in your data table.
- Next is the “Thump Test.” Hold the apple near your ear. Thump the side of your apple with your finger, like you would do to a watermelon. Record how they sound in your data table.
- Have an adult cut open their apple to find out if it is mealy or not. Describe the texture on your data table.
| Day | Date | Apple Appearance | Mass of Apple | Volume of Apple | Density (mass/volume) | Describe “Thump” | Texture of adult’s apple |
| 1 | |||||||
| 2 | |||||||
| 3 | |||||||
| 4 | |||||||
| 5 |
- What claim can you make about apples and mealiness?
- What evidence supports or refutes your “claim”?
- What is your reasoning about which test is the best for identifying a mealy apple? Ask the adult how you should share your results with others.
- How did the density of the apple change over time?
- When did you first notice the apple was becoming mealy? How do you think you could prevent this?
NOTES to Adult:
You will also need 5 apples of the same type and ages as your students. Each time the student makes observations, cut open one of the apples. Give a piece to each student/group. Have them describe the texture on their data table. This can be visual, touch, or taste. I’ll leave that up to you. The apple can also be observed with a hand lens or a stereoscope, if one is available.
This activity should cover a two-week span. Do not refrigerate the apples during this time, but left at room temperature. Ideally, have the students observe the apples twice the first week, and three times during the second week.
Each student or group should share their results with others via poster or presentation.
NGSS
MS-ESS2-1 Earth’s Systems
Develop a model to describe the cycling of Earth’s materials and the flow of energy that drives this process.
Performance Expectation
Grade: Middle School (6-8)
In the apple activity, the student is studying the decomposition of an apple and the changes in its structure. In nature, decomposition is an integral part of any ecosystem.
MS-ETS1-3 Engineering Design
Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
Performance Expectation
Grade: Middle School (6-8)
In this activity, the student is comparing three tests of apple decomposition, evaluating them to determine which one is best.
MS-LS2-3 Ecosystems: Interactions, Energy, and Dynamics
Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
Performance Expectation
Grade: Middle School (6-8)
This activity is the first step in observing changes in an organism that allows recycling in an ecosystem.
More Questions to explore:
Do apples become mealy faster if kept in the refrigerator or on the counter?
If you keep other fruit with an apple, does it ripen faster?