🍎 What keeps a cut apple from going brown?

My hypothesis

If I change what the apple slice is dipped in, then how brown the slice is after an hour will ______, because ______.

🔊 You fill in the blanks. Think about what touches the cut side of the apple, and what each dip might keep away. A guess is a good because: the test finds out.

Change, measure, keep the same

Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 4 levels 3 times.

What you need

• 🍎 An apple: 1 for each try
• 🍋 Lemon juice
• 🧂 Salt
• 🚰 Water from the tap
• 🥛 Clear plastic cups, all the same size: 3, for dipping
• 🍽️ Small plates or saucers, all the same: 1 big one
• 📄 Paper
• 🖍️ Crayons or markers: brown and yellow
• ⏱️ A stopwatch or a kitchen timer
• 🔪 A sharp kitchen knife, for the grown-up

Steps

1. Grown-up: A grown-up cuts the apple into eight slices the same size.🔊
2. Colour a brown scale on paper: 0 is white, 5 is dark brown.🔊
3. Fill three cups: plain water, water with a spoon of salt, and lemon juice.🔊
4. Dip two slices in each cup for one minute, and leave two slices dry.🔊
5. Lay them on a plate with a label beside each pair.🔊
6. After one hour, give every slice a brown score from your scale.🔊
7. Do the whole test on two more days with a new apple.🔊
8. Draw a bar for each dip. Which kept the apple whitest?🔊

One step is a grown-up's, marked above. Write each number down straight away, in the table below, so nothing is lost.

Your results table

From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a bar graph, one bar for each thing you tried.

Why it works

🔊 When an apple is cut, its cells break open and a substance inside them meets the air and turns brown. Lemon juice is sour, an acid, and acid slows that change right down. Salt water and plain water help a little by keeping some of the air off the slice.

Going further (7th and up): Change a second thing: score every slice at 15, 30, 60 and 120 minutes, and draw a line for each dip.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 2nd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed what the apple slice is dipped in and measured how brown the slice is after an hour, in brown score, 0 to 5.
• What did you keep the same, and why does that matter? I kept slices from the same apple and dipping each for the same one minute the same, so the only difference was what the apple slice is dipped in.
• How many times did you test it? 3 times at each of my 4 levels.
• If you did it again, what would you change or test next? I'd score every slice at 15, 30, 60 and 120 minutes, and draw a line for each dip.

Make it yours

Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.

Try next

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