Milk Colouring Activity Worksheet for 11-Year-Olds

Instructions

Today, you're going to become a scientist and an artist all at once! This experiment, sometimes called "Magic Milk," explores how different liquids interact in a colourful, explosive way.

You Will Need:

• A shallow dish or plate with a lip
• Milk (whole milk works best for this!)
• Liquid food colouring (at least 2-3 different colours)
• Liquid dish soap
• A few cotton swabs

Let's Experiment!

1. Carefully pour enough milk into the dish to completely cover the bottom. Let it settle for a minute.
2. Gently add one drop of each of your food colours to the milk. Place the drops near the center of the dish, but don't let them touch each other.
3. Make a prediction! What do you think will happen when you touch the milk with a plain cotton swab?
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4. Now, test it! Take a clean cotton swab and gently touch the tip to the center of the milk. Hold it there for 10 seconds. What happens?
5. Now for the magic! Dip the other end of your cotton swab in the liquid dish soap, getting a good drop on the tip.
6. Predict what will happen when you touch the soapy swab to the milk.
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7. Gently touch the soapy tip of the cotton swab to the center of the milk, right in the middle of the colours. Hold it there and watch what happens!

Observation Corner

Describe or draw what you saw when you touched the milk with the soapy cotton swab. Use exciting words to describe the movement of the colours!

The Science Behind the Fun

What you saw wasn't magic—it was science! Milk is mostly water, but it also contains vitamins, proteins, and tiny droplets of fat. The food colouring just sits on top of the milk.

Milk has something called surface tension, which is like a stretchy, invisible "skin" on its surface. When you first touched it with the clean cotton swab, not much happened because you didn't break that tension.

But dish soap is a special chemical designed to break up fats and grease (which is why it's so good at cleaning greasy pans!). When you added the soap, two things happened at once:

1. The soap immediately broke the surface tension of the milk, causing the liquid to spread out.
2. The soap molecules raced around trying to attach to the fat molecules in the milk.

This rapid movement churned the milk, carrying the food colouring along for the ride and creating the beautiful bursts and swirls of colour you saw!

Think a Little Deeper

Answer the questions below in full sentences.

1. Based on the science, why do you think whole milk (which has more fat) works better for this experiment than skim milk (which has very little fat)?
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2. What do you think would happen if you tried this experiment with water instead of milk? Why?
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Vocabulary Match-Up

Draw a line to connect the scientific term to its correct definition.

Answer Key

Think a Little Deeper:

1. Whole milk works better because it has a higher fat content. Since the soap reacts with the fat, more fat means a bigger and longer-lasting chemical reaction, which creates more colourful swirls.
2. If you used water, the soap would still break the surface tension, and the colours would spread out a little bit. However, the effect would be much less dramatic and would stop quickly because there are no fat molecules for the soap to chase around.

Vocabulary Match-Up:

• 1. Surface Tension matches with D. The invisible "skin" on top of a liquid caused by molecules sticking together.
• 2. Molecule matches with A. The tiny particles that make up substances like water and fat.
• 3. Fat matches with B. A nutrient in milk that soap molecules are attracted to.
• 4. Soap matches with C. A substance that is an expert at breaking down fats and grease.