🧪 Ages 4–10⏱ 10 min + 1 hour waiting🧽 Mess: Very low
The question: Why do cut apples turn brown, and can we stop it?
Make a prediction
Which apple slice will stay the whitest after an hour? Write your guess on the worksheet before you start. Scientists call this a hypothesis.
What you need
1 apple
5 small plates or bowls
Lemon juice
Salt water (1/2 tsp salt in 1/2 cup water)
Plain water
Plastic wrap
A timer
Steps
Ask an adult to cut 5 apple slices about the same size.
Slice 1: leave it alone on a plate (the control).
Slice 2: brush or dip it in lemon juice.
Slice 3: soak it in salt water for 1 minute.
Slice 4: soak it in plain water for 1 minute.
Slice 5: wrap it tightly in plastic wrap.
Check every 15 minutes for an hour and color in the browning on your worksheet.
🔬 Try different apple varieties. Some, like Granny Smith, brown more slowly than others.
⚠️ Safety: An adult should do the cutting.
What's happening? The science
Apple cells contain a natural enzyme (a helper protein) and natural plant chemicals. When you cut an apple, the cells break open and these meet oxygen in the air. The enzyme speeds up a reaction that makes brown pigments. This is called enzymatic browning, and it happens to bananas, avocados and potatoes too.
Lemon juice works two ways: its acid slows the enzyme down, and its vitamin C reacts with oxygen first. Salt water and plastic wrap help by keeping oxygen away from the surface.
Think further
Why might lunch boxes pack apple slices with a squeeze of lemon?
Does cold slow browning? Put one slice in the fridge and compare.
