🥬 Do leaves help celery pull up coloured water?

My hypothesis

If I change how many leaves are left on the stalk, then how far up the stalk the colour climbs in four hours will ______, because ______.

🔊 You fill in the blanks. Think about where water leaves a plant, and what that might do to the water below it. 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 3 levels 3 times.

What you need

• 🥬 A bunch of celery: 9 stalks about the same size
• 🌈 Food colouring: blue or red, the darker the better
• 🚰 Water from the tap
• 🥛 Clear plastic cups, all the same size: 9
• 🥛 A measuring cup
• 🩹 Masking tape, to mark lines
• 🔪 A sharp kitchen knife, for the grown-up
• ✂️ Kid scissors
• 📏 A ruler

Steps

1. Grown-up: A grown-up cuts the bottom 2 cm off nine celery stalks, so each has a fresh end.🔊
2. Leave three stalks with all their leaves, snip half the leaves off three, and all off three.🔊
3. Put a quarter cup of water and 10 drops of food colouring in each of nine clear cups.🔊
4. Stand one stalk in each cup, cut end down, and label the cups.🔊
5. Leave them in a warm, bright room for four hours.🔊
6. Grown-up: A grown-up slices each stalk open from the bottom up, along its length.🔊
7. Measure how far up the stalk the coloured lines reach.🔊
8. The three stalks of each kind are your three trials: write each one in your table.🔊
9. Find the mean for each and draw a bar graph.🔊

2 steps are 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

🔊 Water climbs up celery through thin tubes that run the length of the stalk. Leaves let water dry away into the air through tiny holes, and as it leaves it tugs the water below it up the tubes. With fewer leaves there is less tugging, so the colour usually climbs more slowly.

Going further (7th and up): Change a second thing: stand one set in a sunny window and one in a dark cupboard, and graph light and dark side by side.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 3rd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed how many leaves are left on the stalk and measured how far up the stalk the colour climbs in four hours, in cm.
• What did you keep the same, and why does that matter? I kept stalks about the same size, from the same bunch and the same water and colour in each cup the same, so the only difference was how many leaves are left on the stalk.
• How many times did you test it? 3 times at each of my 3 levels.
• If you did it again, what would you change or test next? I'd stand one set in a sunny window and one in a dark cupboard, and graph light and dark side by side.

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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• 🌈 Does food colouring spread faster in hot water?2nd–8th grade · 1 day of testing · free🧪 Water, ice and mixing · 🧂 Kitchen things