HAL5’S Lava Layers

a.k.a. Mini Lava Test Tubes

Do you know why you have to shake most salad dressing bottles before using?
Why don’t oil and water mix?
What kind of stuff you can float between oil and water layers?

This activity will attempt to show you why oil and water don’t mix by making your own Test Tube Lava Layers! How cool is that? You can experiment with a larger version of the Lava Layer at home using what you will learn here, with your parent’s help of course. Ideas for further investigation at home are down below.

This activity will attempt to show you why oil and water don’t mix by making your own Test Tube Lava Layers! How cool is that? You can experiment with a larger version of the Lava Layer at home using what you will learn here, with your parent’s help of course. Ideas for further investigation at home are down below.

In the Panoply Lava Layer activity, we will be using:

  • plastic test tube
  • plastic disposable pipettes
  • baby oil
  • water
  • food coloring
  • plastic sequins

Basic Chemistry

Oil and water don’t mix because of two reasons:

Reason #1. Oil and water have different densities:

lava layers2Density is the term we used to describe how molecules are packed together in a medium. A medium can be liquid, solid, or air/gas. Density is measured in the unit of weight per volume, like pounds per cubic foot or gram per cubic centimeter.

When we put oil and water into the same container, the fluid that has the higher density will sink; while the fluid with the lighter density floats. Typically, baby oil has a density of about 0.83 grams per cubic centimeter (g/cm3) while water has a density of 1.0 g/cm3. Based on this, if water and baby oil are put together into a container, which do you think will float? Which will sink?

However, combining both of these will only give you the ‘layers’ effect, like multi-layer Jell-O or stacked popsicle sticks. But what happens if you try to mix the water and baby oil? Why don’t they stay mixed?

Reason #2. Oil and water have different charges:

Water molecules are strongly attracted to each other because, in chemistry terms, they are polar. Polar molecules have either a concentration of positive or negative electric charge. Water’s polar bond makes them love to attract to each other. Since water is a polar compound, it is only soluble, or dissolvable, in other polar compounds.

Oil molecules are non-polar and hydrophobic. Hydrophobic means “water-fearing” so oil does not like water. Because of the molecules’ charge, oil molecules will ultimately stick to each other. Therefore, even if you stir a container with oil and water, they will eventually separate into two distinct layers. Find out more about this by researching Chemistry – Polar Bonds!

To make it a little easier to show the different lays of oil and water, we can use food coloring to color the water. Luckily food coloring is hydrophilic, or “water-loving”, so when we add a drop of green food color, it will sink through the oil layer to the water layer and dissolve in the water!

Floating Stuff in Oil and Water

As we’ve already learned, different materials have different densities. Small stuff like glitter and sequins can float on water since things float when they are buoyant, or less dense than the fluid they’re in. So, when we drop plastic sequins into the lava tube, they will sink through the oil, because of their weight, and some of which will get caught in the water layer. We can shake them around and see what happens. What do you notice?

Additional Home Experiment Ideas

lava layersAt home, we can use a larger water bottle or glass jar, and introduce Alka-Seltzer tablets into the water and oil mixture. Alka-Seltzer tablet interact with water, to create fizz or carbon dioxide, like soda. When we drop a small piece of Alka – Seltzer into the oil and water mixture, it will sink to the water layer and then fizz.  The carbon dioxide bubbles will rise to the top of the bottle, as it is lighter than both water and oil. As this happens, it creates a neat, simple lava lamp.

Materials:

  • Water
  • 1/16 Alka-Seltzer tablet
  • 5 drops food coloring
  • Vegetable oil or baby oil
  • Pinch of glitter
  • Plastic bottle

Instructions:

  1. Fill ¾ bottle with oil and ¼ water
  2. Add 5 drops of food coloring into the bottle
  3. Drop 1/16 pill of Alka-Seltzer and
  4. Observe the reaction

 

Questions:

  1. What were your observations?
  1. Why do big bubbles form and why do they float to the surface?
  1. What would happen if you put in more Alka-Seltzer?
  1. Less Alka-Seltzer?
  1. How would this experiment work in space?
    1. What would happen?
    2. Would the bubbles rise to the top of the container?
    3. Would the liquids separate due to their densities?

Additional Website Links

http://littlebinsforlittlehands.com/5-easy-science-discovery-bottles/

http://alittledelightful.com/2014/04/diy-sensory-bottles.html

http://www.moonfrye.com/diy/magic-bottles/

 

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