Ocean Layers in a Jar

Have you ever wondered why it's easier to float in the ocean than in a swimming pool? Would you believe us if we told you the secret is... salt?

In this experiment, we’ll learn more about our moana (oceans) by creating different coloured salty solutions and observing how they interact and layer. The moana is connected to the star Waitā in the Matariki cluster. Waitā is associated with saltwater, alongside the food and animals that come from the sea and our relationship with the ocean world.

Get ready to explore the secret science of salt—and how it helps shape the sea!

Before we get started, let's make some guesses about what might happen. Scientists like to make predictions, or hypotheses, before they do experiments. It helps them figure out what to expect and why things happen the way they do.

Have a go at making your best guess using the pātai (questions) below:

1. Do you think that the different salty mixtures will look different before you put the food colouring in?
2. What effect do you think the salt will have on the water?

Tīmata! Let’s get started! 

• Ipu roa - A tall, thin clear container
• E toru ngā kōata - Three glasses (to hold different concentrations of salty water)
• Ipu ine - Measuring cup
• Tīpune - Teaspoon
• Tote - Salt
• Wai pūmahana - Warm water
• Kara kai - Food colouring (one colour for each concentration of salty water)
• Pune - Spoon
• Ngōpata - Liquid dropper or syringe

Let's begin!

1. Pour 100 mL of warm water into each of three glasses.
2. Add 4 teaspoons of salt to the first glass, 2 teaspoons of salt to the second glass, and no salt to the third glass.
3. Stir each glass well using a spoon until the salt is fully dissolved.
4. Add 1–2 drops of food colouring to each glass, ensuring you choose a different colour for each glass. Make sure you remember or label which colour goes with which salt level!
5. First, use your liquid dropper to add the most salty liquid (from the glass with 4 teaspoons of salt) into your tall, thin container.
6. Next, slowly and carefully add the liquid from the glass with 2 teaspoons of salt on top - one drop at a time.
7. Finally, add the liquid with no salt in the same way.

1. What did you notice about how the colours moved (or didn’t move) when you added them to the same container?
2. Why do you think we used warm water?

Salty water weighs more!

This experiment works because of something called density. Density is a way to describe how much "stuff" is packed into a certain amount of space.

The most salty water has the most salt stuffed into the same amount of water. Even though you can't see the salt anymore, it's still there—making the water heavier.

Because heavier (denser) liquids sink below lighter (less dense) ones, the salty water stays at the bottom and the less salty water floats on top—if you add them slowly and carefully!

This experiment connects to Waitā, the star linked to saltwater and the ocean, reminding us how the properties of water affect marine life, currents, and the world beneath the waves.