🍇 Do raisins dance longer in fizzy water?

My hypothesis

If I change what kind of water the raisin is in, then how many times the raisin rises to the top in two minutes will ______, because ______.

🔊 You fill in the blanks. Think about what could lift a heavy raisin up, and what happens to it at the top. 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

• 🫧 Plain fizzy water (club soda or seltzer), freshly opened: 2 small bottles, one opened the night before
• 🚰 Water from the tap
• 🍇 Raisins: 9, the same size
• 🥛 Clear plastic cups, all the same size: 9, the same size
• 🥛 A measuring cup
• 🥄 A spoon
• ⏱️ A stopwatch or a kitchen timer
• 🩹 Masking tape, to mark lines

Steps

1. The night before, pour half a cup of fizzy water into each of three clear cups and leave them out, uncovered.🔊
2. Next day, open a fresh bottle and pour half a cup of fizzy water into three more clear cups.🔊
3. Pour half a cup of tap water into three more clear cups.🔊
4. Label the cups with tape: old fizz, fresh fizz and tap.🔊
5. Slide one raisin into a cup and start the timer.🔊
6. Count each time the raisin floats all the way up to the top in two minutes.🔊
7. Write the count in your table, and lift the raisin out with a spoon.🔊
8. Test the other cups one at a time with a new raisin each time, fresh fizz first.🔊
9. Fill in your table with all nine counts, and draw a bar graph.🔊

Every step is one you can do yourself, with a grown-up nearby. 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

🔊 Fizzy water is full of bubbles of carbon dioxide gas. The bubbles stick to a raisin's wrinkly skin and lift it to the top, where they pop, so the raisin sinks and picks up more bubbles. Fizzy water left open overnight loses most of its gas, so its raisins usually dance much less.

Going further (7th and up): Change a second thing: shake the fizzy water gently before pouring, and graph the rises for shaken and still water.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 1st grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed what kind of water the raisin is in and measured how many times the raisin rises to the top in two minutes, in rises.
• What did you keep the same, and why does that matter? I kept raisins of the same size and half a cup of water in every cup the same, so the only difference was what kind of water the raisin is in.
• 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 shake the fizzy water gently before pouring, and graph the rises for shaken and still water.

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 more baking soda make a bigger fizz?3rd–8th grade · 1 day of testing · free🧪 Water, ice and mixing · 🧂 Kitchen things