DIY: Water Ring | Tinkerer Box Blog

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Water Ring

Stem Activities

Ages: 3-5

Less than 30 minutes

Grownup needed

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Have you ever wondered why oil forms circles in water? This simple yet magical experiment will help you solve this puzzle! You'll experience the fascinating interaction between oil and water while exploring the amazing science of surface tension.

Materials Needed

Cooking oil
Glass bowl
Water
Dropper
Lolly stick
Colour powder (chalk dust)
Toothpick
Washing-up liquid

An assortment of items are arranged on a light woodgrain table, seemingly for a science experiment or demonstration. These include: a small glass bowl containing oil, a larger empty glass bowl, a tall glass of water, a clear pipette or dropper, a wooden craft stick, two crayons (one orange an

Step-by-step tutorial

Step 1

Using a lolly stick, mix some colour powder into the cooking oil until well combined.

Two hands hold an orange crayon and a wooden craft stick over a clear glass bowl containing a small amount of orange powder or shavings, likely grated from the crayon. The hands appear to be in the process of either grating the crayon with the stick or mixing the crayon shavings into something within the bowl. The bowl sits on a light woodgrain surface. This image likely depicts a craft or science activity.

Step 2

Pour water into the empty bowl.

A hand pours water from a tall, clear drinking glass into a clear glass bowl. The bowl already contains a small amount of water. Both the glass and bowl sit on a light woodgrain surface. This image likely depicts a step in preparing for a science experiment, craft, or other activity involving water.

Step 3

Use the dropper to draw up 3ml of coloured cooking oil.

A hand holds a clear plastic pipette containing orange liquid over a small, clear glass bowl. The bowl contains a vibrant orange liquid, and a drop from the pipette is about to fall into it. The bowl rests on a light woodgrain surface. This image likely depicts a science experiment or demonstration involving mixing or measuring colored liquids.

Step 4

Drop the cooking oil from the dropper into the water.

A hand holds a clear pipette containing blue liquid over a clear glass bowl filled with water. The pipette is positioned as if about to dispense the blue liquid into the bowl. In the background, a test tube rack containing test tubes filled with various colored liquids is visible, along with a small, whimsical, googly-eyed bottle or flask. The scene is set on a light woodgrain surface, suggesting a science experiment or demonstration involving color mixing or liquid solutions.

Step 5

Dip a toothpick in washing-up liquid and touch it to the centre of the oil. Watch carefully as the oil spreads out from the toothpick, forming a beautiful ring.

A small, bright blue sphere or blob of a gel-like substance floats in a clear glass bowl filled with water. The bowl sits on a light woodgrain surface. A toothpick is partially visible on the right side of the frame. In the background, a test tube rack with various colored liquids and a small, googly-eyed flask or bottle are visible. This image likely depicts a science experiment or demonstration, possibly illustrating concepts like density or immiscibility.

The Science Behind It:

Why does oil form circles in water?

This relates to surface tension between molecules. Oil and water have different molecular structures that prevent them from mixing easily. Water molecules form strong hydrogen bonds, giving water high surface tension, while oil molecules tend to "self-aggregate". When oil contacts water, the attractive forces between oil molecules cause them to minimise contact with water, forming a circle to maximise molecular bonding whilst reducing surface area, reaching a stable state.

What does the washing-up liquid do?

Washing-up liquid is a surfactant. When added to the oil-water mixture, it reduces the surface tension at the interface, preventing oil molecules from clustering as tightly together, resulting in the ring formation.

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