Does whole milk swirl farther than skim milk?
- 🚫 Not food
- 🚫 Test food is not for eating
- 🧼 Wash your hands after
My hypothesis
If I change how much fat is in the milk, then how far the colour spreads across the milk in one minute will ______, because ______.
You fill in the blanks. Think about what is different between the three milks, and what the soap grabs onto. A guess is a good because: the test finds out.
Change, measure, keep the same
CHANGE
how much fat is in the milk: Skim milk, 2% milk, Whole milk
MEASURE
how far the colour spreads across the milk in one minute, in cm
KEEP THE SAME
- the same amount of milk on each plate
- one drop of the same food colouring each time
- the same dip of soap on the pencil eraser
- milk at the same temperature
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 little skim, 2% and whole milk
- Small plates or saucers, all the same: 3, white if you can
- Food colouring: one dark colour
- Dish soap
- A new pencil with an eraser on the end
- Masking tape, to mark lines
- A sponge or cloth, for wiping up
- 📏 A ruler
Steps
- Label three plates skim, 2% and whole with masking tape.
- Pour enough of the right milk to cover the bottom of each plate, the same amount on every plate.
- Wait a moment for the milk to stop moving.
- Put one drop of food colouring in the middle of the first plate.
- Dip the eraser end of a pencil 1 cm deep in dish soap, then touch it to the middle of the colour.
- Watch for one minute, then measure how far the colour has spread, from edge to edge.
- Do the same on the other two plates, one at a time.
- Tip out the milk, wash the plates and the pencil, and do it two more times.
- Fill in your table and draw a bar graph, with one bar for each milk.
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
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
I changed: Milk I measured: how far the colour spreads across the milk in one minute (cm)
| Milk | Try 1 (cm) | Try 2 (cm) | Try 3 (cm) | Mean |
|---|---|---|---|---|
| Skim milk | ||||
| 2% milk | ||||
| Whole milk |
MY GRAPH (a bar graph: milk along the bottom, cm up the side)
What I noticed: ______________________________________________
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.
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
If I change how much fat is in the milk, then how far the colour spreads across the milk in one minute will ________________, because _____________________________________________
| I CHANGE | I MEASURE | I KEEP THE SAME |
|---|---|---|
| Milk: Skim milk, 2% milk, Whole milk | how far the colour spreads across the milk in one minute (cm) |
|
What I think will happen, in my own words:
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does whole milk swirl farther than skim milk?
My hypothesis was ☐ right ☐ partly right ☐ not right.
I know because my numbers show:
What surprised me, or what might have gone wrong (7th and up):
Next time I would test:
Idea: Change a second thing: use whole milk at fridge-cold, room and warm temperature, and graph the spread against the temperature.
Why it works
Milk is mostly water with tiny drops of fat floating in it, and soap grabs onto fat. As the soap rushes along looking for fat, it pushes the milk around and drags the colour with it. Milk with more fat gives the soap more to chase, so the swirl usually travels farther.
Going further (7th and up): Change a second thing: use whole milk at fridge-cold, room and warm temperature, and graph the spread against the temperature.
Board layout
- ❓ Question (10 × 8 in): Does whole milk swirl farther than skim milk?
- 💭 Hypothesis (10 × 9 in): If I change how much fat is in the milk, then how far the colour spreads across the milk in one minute will ______, because ______.
- 🧺 Materials (10 × 12 in): 7 things: see your list.
- 🪜 Steps (22 × 9 in): 9 steps, three tries at each level.
- 📊 Results (22 × 16 in): Your table (Milk down the side, tries across) and your bar graph.
- ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…
Materials to list: A little skim, 2% and whole milk; Small plates or saucers, all the same; Food colouring; Dish soap; A new pencil with an eraser on the end; Masking tape, to mark lines; A sponge or cloth, for wiping up.
Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.
This project at your grade
| 1st–3rd grade | Tries: three at each level (one is fine at a first fair). The table: levels and tries, numbers or pictures. The graph: a picture, or a simple bar graph. The conclusion: what happened, in their words. |
|---|---|
| 4th–6th grade | Tries: three at each level. The table: units in the header and a mean column. The graph: a bar graph, or a line for a number that grows. The conclusion: right, partly or not, and the numbers that show it. |
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 how much fat is in the milk and measured how far the colour spreads across the milk in one minute, in cm.
- What did you keep the same, and why does that matter? I kept the same amount of milk on each plate and one drop of the same food colouring each time the same, so the only difference was how much fat is in the milk.
- 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 use whole milk at fridge-cold, room and warm temperature, and graph the spread against the temperature.
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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🔨 From the Workshop: this project grows from a Workshop build, with picture steps of its own.
👨👩👧 For grown-ups and teachers: how much to help, the safety rules, and running a school fair. Science fair v0.16.1 · Checked .