🍬 Which liquid dissolves a hard candy fastest?

My hypothesis

If I change the liquid the candy sits in, then how wide the candy is after 30 minutes will ______, because ______.

🔊 You fill in the blanks. Think about which of these liquids is mostly water, and which one does not mix with sugar. 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

• 🍬 Round hard candies, all the same kind: 13, all the same kind
• 🚰 Water from the tap
• 🚰 Warm water: warm from the tap, never hot
• 🍶 White vinegar
• 🛢️ Cooking oil
• 🥛 Clear plastic cups, all the same size: 12, the same size
• 🥛 A measuring cup
• 🥄 A spoon
• 🍽️ Small plates or saucers, all the same: 1
• ⏱️ A stopwatch or a kitchen timer
• 🩹 Masking tape, to mark lines
• 📏 A ruler

Steps

1. Label twelve clear cups with tape: three each for tap water, warm tap water, vinegar and oil.🔊
2. Pour half a cup of the right liquid into each cup.🔊
3. Measure across the middle of one candy in mm, and check that the others look the same size.🔊
4. Slide one candy into each cup, and start the timer when the last one is in.🔊
5. Do not stir, shake or bump the cups.🔊
6. After 30 minutes, lift each candy out with a spoon and lay it on a plate.🔊
7. Measure how wide each candy is now, across the middle. If it is gone, write 0.🔊
8. Write each width in your table. Throw the candies away: do not eat them.🔊
9. Find the mean width for each liquid, 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

🔊 Hard candy is mostly sugar, and sugar dissolves in water: the water pulls tiny bits of sugar away one at a time. Warm water moves faster, so it usually pulls faster. Vinegar is mostly water too, but oil does not mix with sugar at all, so it leaves the candy alone.

Going further (7th and up): Change a second thing: soak candies in warm tap water for 10, 20 and 30 minutes, and draw a line of width against time.

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 the liquid the candy sits in and measured how wide the candy is after 30 minutes, in mm.
• What did you keep the same, and why does that matter? I kept candies of the same kind and size and half a cup of liquid in every cup the same, so the only difference was the liquid the candy sits 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 soak candies in warm tap water for 10, 20 and 30 minutes, and draw a line of width against time.

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

• 🥄 Does stirring make sugar dissolve faster?1st–5th grade · 1 day of testing · free🧪 Water, ice and mixing · 🧂 Kitchen things
• 🍬 Does sugar dissolve faster in warm water?2nd–6th grade · 1 day of testing · free🧪 Water, ice and mixing · 🧂 Kitchen things