🖊️ How many colours hide in a marker's ink?

My hypothesis

If I change the colour of the marker, then how many bands of colour show on the strip will ______, because ______.

🔊 You fill in the blanks. Think about whether one colour of ink is really one colour, and what the water carries along. 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

• 🖊️ Washable markers: black, brown, green and purple: one of each colour
• ⚪ Round paper coffee filters: 3
• 🚰 Water from the tap
• 🫙 A clear jar or tall glass: a wide glass
• ✏️ A pencil
• ⏱️ A stopwatch or a kitchen timer
• ✂️ Kid scissors
• 📏 A ruler
• 🩹 Tape

Steps

1. Cut twelve strips, 1 cm wide and 10 cm long, from flat coffee filters.🔊
2. Draw a pencil line 2 cm up from the bottom of each strip.🔊
3. Make a fat dot of marker on each line: three strips each of black, brown, green and purple.🔊
4. Write the marker colour at the top of each strip in pencil.🔊
5. Pour 1 cm of water into a wide glass.🔊
6. Tape four strips, one of each colour, to a pencil laid across the glass.🔊
7. Slide the strips so their bottoms touch the water and the dots stay dry above it.🔊
8. Wait until the water has climbed near the top. That takes about fifteen minutes.🔊
9. Lift the strips out, lay them flat, and count the bands of colour on each strip.🔊
10. Write each count in your table, then do it two more times with new strips.🔊
11. Find the mean for each marker, 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

🔊 Many marker inks are mixtures of different coloured dyes. Water creeps up the paper and carries the dyes along, but each dye travels at its own speed, so they spread out into separate bands. This way of splitting a mixture is called chromatography.

Going further (7th and up): Change a second thing: use a washable marker and a permanent marker of the same colour, and graph the bands for each.

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 colour of the marker and measured how many bands of colour show on the strip, in bands of colour.
• What did you keep the same, and why does that matter? I kept strips cut from the same kind of coffee filter and the same size of dot the same, so the only difference was the colour of the marker.
• 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 use a washable marker and a permanent marker of the same colour, and graph the bands for each.

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

• 📄 Which paper pulls water up the highest?2nd–6th grade · 1 day of testing · about $1🧪 Water, ice and mixing · 🧂 Kitchen things
• 🌈 Does food colouring spread faster in hot water?2nd–8th grade · 1 day of testing · free🧪 Water, ice and mixing · 🧂 Kitchen things