Lava Lamp

Have you ever thought about how heavy water is? Even though it looks light and clear, it actually has weight! But what about oil—do you think it’s heavier or lighter than water? In this experiment, we’ll explore how different liquids stack up because of weight and use the power of science to create our very own groovy lava lamp!

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 questions below:

1. Do you think the oil and water will mix inside the bottle?
2. If the experiment makes bubbles, do you think the bubbles will rise to the top, sink to the bottle or stay in the middle of the liquid?

Tīmata! Let’s get started! 

• A Clear Plastic Bottle - ipu
• Water - wai
• Vegetable Oil - hinu huawhenua
• Food Colouring - kara kai  (optional)
• Alka-Seltzer Tablet (alternatively you can use baking soda and vinegar) 

Let's begin!

1. Fill the bottle (ipu) about two-thirds full with vegetable oil (hinu huawhenua).
   
2. If using baking soda and vinegar: Add 2 tablespoons of baking soda to the bottle before pouring in the vegetable oil.
   
3. Carefully pour water into the bottle, filling it almost to the top. The water will sink below the oil because it is denser. If you are using the baking soda and vinegar method, leave some space at the top for the vinegar to be added later—otherwise, the bottle may overflow!
   
4. To make your lava lamp bubble:
   • Alka-Seltzer method: Break an Alka-Seltzer tablet into pieces and drop them into the bottle.
   • Baking soda & vinegar method: Pour ¼ cup of vinegar into the bottle and watch the reaction!

Extra for Experts!

• For an even cooler effect, shine a light under the lava lamp in a dark room.
• Test how different types of oils changes your lava lamp.

1. What did you see?
2. What did you hear?
3. How did the gas created inside the bottle affect the movement of your bottle boat?
4. Why do you think the bottle needed to be sealed, except for the straw?
5. If you were to design a better bottle boat, what would you change or improve? 
   

Oil and Water Don’t Mix:

This is because oil and water have different densities and different charges (yes, even liquids have an electrical charge!)

When you add water and oil together, the water will always form a layer at the bottom of the container because water is denser that oil, or in other words the water molecules are packed closer together than oil molecules, so it weighs  more.

Why the Bubbles Move:

The fizzing from the chemical reaction that occurs when you add Alka-seltzer or baking soda + vinegar creates carbon dioxide gas.

The gas bubbles are less dense than the water, so they rise up. Once the bubbles pop, the water becomes heavier and sinks again. This creates the "lava lamp" effect of moving, rising, and falling coloured water.