Science Fair

Grown-ups

Does dish soap stop oil and water from separating?

3rd–8th grade · 1 day of testing · free · ages 8 to 14 · 60 minutes a sitting

  • 🚫 Not food
  • 🧽 A bit messy
What you need for the oil, water and soap project: cooking oil, water from the tap, dish soap, food colouring, a clear jar or tall glass

My hypothesis

If I change how much dish soap goes in, then how long the oil and water take to split back into two layers will ______, because ______.

You fill in the blanks. Think about what dish soap does to greasy plates, and what that might do to tiny drops of oil. A guess is a good because: the test finds out.

Change, measure, keep the same

CHANGE

how much dish soap goes in: 0 drops, 5 drops, 10 drops, 20 drops

MEASURE

how long the oil and water take to split back into two layers, in seconds

KEEP THE SAME

  • the same jar with its lid on tight
  • the same amounts of oil and water
  • shaking it the same way, 20 times

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

  • Cooking oil: a quarter cup
  • Water from the tap: a quarter cup
  • Dish soap
  • Food colouring: 1 drop, so the water is easy to see
  • A clear jar or tall glass: 1 with a tight lid
  • A measuring cup
  • A stopwatch or a kitchen timer

Steps

  1. Pour a quarter cup of water and a quarter cup of oil into a clear jar with a lid.
  2. Add one drop of food colouring, so the water layer is easy to see.
  3. Screw the lid on tight and shake it 20 times.
  4. Set it down, start the timer, and watch the side of the jar.
  5. Stop the timer when a clear line shows between the oil and the water, and write it down.
  6. If no line shows after 10 minutes, write 600 seconds and stop.
  7. Shake and time it two more times.
  8. Add 5 drops of dish soap and do three more shakes and timings.
  9. Add soap up to 10 drops, then up to 20, and do three tries at each.
  10. Find the mean time for each amount and draw a line 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

MY RESULTSPeabody 🦉 peabody.kids/science-fair

Name ______________________ Fair day ____________

Question: Does dish soap stop oil and water from separating?

I changed: Drops of dish soap   I measured: how long the oil and water take to split back into two layers (seconds)

Drops of dish soapTry 1 (seconds)Try 2 (seconds)Try 3 (seconds)Mean
0 drops
5 drops
10 drops
20 drops

MY GRAPH (a line graph: drops of dish soap along the bottom, seconds 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 line graph, because the thing you change is a number that goes up.

📊 Make my graph🖨 Print the whole packet (9 pages)

Why it works

Oil and water don't mix: the water bits cling to each other and squeeze the oil out, so the oil floats up into its own layer. Soap is made of tiny bits with one end that holds on to water and one end that holds on to oil. They coat the oil drops and keep them apart, so the drops take much longer to join up and float to the top.

Going further (7th and up): Change a second thing: keep 10 drops of soap and shake 10, 20 and 40 times, and draw a line for how long it stays mixed.

Board layout

MY BOARD · 36 × 48 in tri-foldPeabody 🦉 peabody.kids/science-fair
  1. ❓ Question (10 × 8 in): Does dish soap stop oil and water from separating?
  2. 💭 Hypothesis (10 × 9 in): If I change how much dish soap goes in, then how long the oil and water take to split back into two layers will ______, because ______.
  3. 🧺 Materials (10 × 12 in): 7 things: see your list.
  4. 🪜 Steps (22 × 9 in): 10 steps, three tries at each level.
  5. 📊 Results (22 × 16 in): Your table (Drops of dish soap down the side, tries across) and your line graph.
  6. ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…

Materials to list: Cooking oil; Water from the tap; Dish soap; Food colouring; A clear jar or tall glass; A measuring cup; A stopwatch or a kitchen timer.

Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.

This project at your grade

1st–3rd gradeTries: 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 gradeTries: 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.
7th grade and upTries: three or more at each level. The table: a mean for every level of both tests. The graph: a graph with two lines or two sets of bars. The conclusion: the numbers, what might have gone wrong, and a next question. Second variable: keep 10 drops of soap and shake 10, 20 and 40 times, and draw a line for how long it stays mixed.

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 much dish soap goes in and measured how long the oil and water take to split back into two layers, in seconds.
  • What did you keep the same, and why does that matter? I kept the same jar with its lid on tight and the same amounts of oil and water the same, so the only difference was how much dish soap goes 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 keep 10 drops of soap and shake 10, 20 and 40 times, and draw a line for how long it stays mixed.

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

👨‍👩‍👧 For grown-ups and teachers: how much to help, the safety rules, and running a school fair. Science fair v0.16.1 · Checked .

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