Educational Resources Lets Talk Science Challenge participants

A variety of lava lamps

A variety of lava lamps (Dean Hochman [CC BY 2.0], Wikipedia)

STEM in Context

Lava Lamps

Genie Leung & Let's Talk Science

Summary

Lava lamps are very interesting to look at. But they are also interesting examples of buoyancy, heat transfer and solubility!

What do you think about when you hear the word “groovy”? Bell bottom pants? Flowers? What about lava lamps?

Lava lamps were very popular back in the groovy 1960s! Many people still have them at home today. 

Most lamps light up a room. But lava lamps are mainly just fun to look at. They have coloured wax globules floating around in a transparent liquid. 

Did you know?

Edward Craven-Walker designed the lava lamp. He based it on an egg timer he saw in a pub! The egg timer had a ball of wax suspended in water. When the wax melted, the egg was ready to eat. 

Lava lamps are also a “groovy” way of seeing physics and chemistry principles in action.

The three states of matter are solids, liquids and gases
The three states of matter are solids, liquids and gases (© 2019 Let’s Talk Science).

What is the Kinetic Molecular Theory?

To understand how lava lamps work, you have to understand Kinetic Molecular Theory. It states that all matter is made up of molecules that are always moving. These molecules have kinetic energy. The amount of energy depends on the temperature. When it’s hotter, molecules have more energy. And when they have more energy, they move faster. There are three most common states of matter.

The molecules in solids have the least energy. That means they move more slowly than molecules in liquids and gases.

The molecules in gases have the most energy of all. They move the fastest.

How Is Kinetic Energy Related to Density?

Kinetic molecular theory can help you understand density. Density refers to how much matter there is in a given volume of space. 

Have you ever thrown a coin into a fountain or a rock into a pond? You probably noticed that these objects sink in water. And you’ve probably noticed that other objects, like twigs, float on water. The objects that are denser than water sink. And the objects that are less dense than water float. 

But what does this have to do with lava lamps? Remember the globules - let’s call them “globs” for short - that float around? At room temperature, the globs are a bit denser than the surrounding liquid. That’s why they sit at the bottom of the lamp. But when you turn the lamp on, the globs heat up. The molecules move faster. The globs become less dense than the surrounding liquid. They rise and start to float around!

Did you know?

Hot air balloons work the same way as the globs in the lava lamp.

How does the ability to mix affect how a lava lamp works?

Chocolate milk on the left and salad dressing on the right
Chocolate milk on the left and salad dressing on the right (Sources: Mae Mu via Unsplash and wwing via iStockphoto).

So why don’t the globs of wax in a lava lamp mix with the surrounding liquid? 

Think about chocolate syrup and milk. They’re miscible liquids. That means they can mix to form a homogeneous mixture.  The chocolate syrup mixes completely with the milk to form yummy chocolate milk!

But some liquids are immiscible. They don’t mix with each other. It all depends on the force of attraction between the molecules in the two liquids.

For example, what happens when you try to mix oil and vinegar - like in a salad dressing? The molecules in the vinegar are more attracted to each other than to the molecules in oil. The molecules in oil are more attracted to each other than to the molecules in the vinegar. No matter how much you shake or stir your dressing, they will never stay mixed together.

But chocolate syrup molecules are attracted to milk molecules. And milk molecules are attracted to chocolate syrup molecules. That’s why you get chocolate milk and not a lava lamp in a glass!

Each immiscible liquid is called a phase. A mixture with two immiscible liquids is called a biphasic mixture. A mixture with more than two immiscible liquids is called a multiphasic mixture.

When you watch the globs float around in a lava lamp, you’re looking at a biphasic mixture!

Did you know?

The globs in a lava lamp are made of paraffin wax. That’s the same type of wax used in many candles and crayons!

Why Do the Globs in a Lava Lamp Move Around?

One of the most interesting features of a lava lamp is the way that the globs float around. But why does this happen? You know that the globs are less dense than the surrounding liquid. And you know that the globs and the liquid are immiscible. So why don’t the globs just rise to the top of the lamp and stay there?

Well, lava lamps are designed so that the temperature at the top is a bit cooler than at the bottom. And what happens to molecules when they cool down? That’s right! They lose energy and move closer together. So when a glob reaches the top of the lava lamp, it contracts. It becomes denser than the surrounding liquid and begins to sink. When it reaches the bottom, the whole cycle repeats!

A lava lamp is an example of a convection current. Convection currents cause liquids and gases to rise and fall because of changes in their density. There are convection currents all around you, even in the Earth’s crust! 

When globs get warmed by the light bulb they rise to the top of the lamp, where they cool and sink. Then, the process begins again
When globs get warmed by the light bulb they rise to the top of the lamp, where they cool and sink. Then, the process begins again (Let’s Talk Science using an image by Saltmiser [CC BY-SA 3.0] via Wikimedia Commons).

Want to Try a Lava Lamp Experiment?

You can build your own lava lamp in your classroom or at home! Here’s what you’ll need:

  • A transparent container, like an empty water or soda bottle

  • Water

  • Vegetable oil

  • Food colouring

  • An effervescent tablet (like Alka-Seltzer®)

  • A flashlight (optional)

 

How to make a lava lamp:

  1. Fill one quarter of the bottle with water

  2. Add food colouring

  3. Fill the rest of the bottle with vegetable oil

  4. Add half an effervescent tablet

  5. Optional: if you have a flashlight, go to a dark room, turn on the flashlight and watch your groovy new lamp in the dark!

 

And there you have it: your very own lava lamp. Watch what happens to these immiscible liquids. Pretty groovy, don’t you think?

Starting Points

Connecting and Relating
  • Have you observed a lava lamp first-hand? What did you think of it? 
  • Would you like to own a lava lamp? Why or why not? 
  • Can you think of any mixtures you have seen that have globules in them? Is there anything you have tried to mix that has distinct layers? 
Connecting and Relating
  • Have you observed a lava lamp first-hand? What did you think of it? 
  • Would you like to own a lava lamp? Why or why not? 
  • Can you think of any mixtures you have seen that have globules in them? Is there anything you have tried to mix that has distinct layers? 
Relating Science and Technology to Society and the Environment
  • Provide examples of convection currents in the natural environment. 
  • You might have seen the word “homogenized” on a carton of milk or on a jar of peanut butter. What does this mean? Why is this done by food manufacturers?
Relating Science and Technology to Society and the Environment
  • Provide examples of convection currents in the natural environment. 
  • You might have seen the word “homogenized” on a carton of milk or on a jar of peanut butter. What does this mean? Why is this done by food manufacturers?
Exploring Concepts
  • What is kinetic energy? How does kinetic energy change matter?
  • How does the Kinetic Molecular Theory help explain changes in the density of matter?  
  • How does the Kinetic Molecular Theory explain what happens to water as it changes states from solid ice to liquid water and then to water vapour or steam?
  • How are convection currents formed in a lava lamp? How are convection currents formed under the Earth’s crust?
Exploring Concepts
  • What is kinetic energy? How does kinetic energy change matter?
  • How does the Kinetic Molecular Theory help explain changes in the density of matter?  
  • How does the Kinetic Molecular Theory explain what happens to water as it changes states from solid ice to liquid water and then to water vapour or steam?
  • How are convection currents formed in a lava lamp? How are convection currents formed under the Earth’s crust?
Nature of Science/Nature of Technology
  • In which fields of science and technology would it helpful to understand the Kinetic Molecular Theory?
Nature of Science/Nature of Technology
  • In which fields of science and technology would it helpful to understand the Kinetic Molecular Theory?
Media Literacy
  • How would you market a lava lamp to kids so that it was both cool and educational? What message would you give about the product so that kids would want to buy one?
Media Literacy
  • How would you market a lava lamp to kids so that it was both cool and educational? What message would you give about the product so that kids would want to buy one?
Teaching Suggestions
  • This article supports teaching and learning of Science, Chemistry, Physics, and Heat and Energy related to buoyancy, fluids, heat transfer, and mixtures & solutions. Concepts introduced include globules, Kinetic Molecular Theory, kinetic energy, solids, liquids, gases, density, miscible, homogeneous mixture, immiscible, phase, biphasic mixture, multiphasic mixture, contracts and convection current. 
  • Before reading this article, teachers could have students complete a Vocabulary Preview learning strategy to engage prior learning and introduce new terminology. Ready-to-use Vocabulary Preview reproducibles for this article are available in [Google doc] and [PDF] formats. 
  • To consolidate understanding after reading the article, teachers could have students complete a Concept Definition Web learning strategy for the concept of Kinetic Molecular Theory. Ready-to-use Concept Definition Web reproducibles for this article are available in [Google doc] and [PDF] formats. 
  • To consolidate an understanding of different types of mixtures, teachers could have students create a graphic organizer, like a T-chart, to compare and contrast heterogeneous and homogeneous mixtures.
  • To further explore miscible and immiscible mixtures, teachers could have students do the hands-on activity What happens when we mix liquids? (Hands-on Activities). 
  • There are various applications of mixtures that could be used for cross-curricular art projects as well. For example, wax resist art and paper marbling.
Teaching Suggestions
  • This article supports teaching and learning of Science, Chemistry, Physics, and Heat and Energy related to buoyancy, fluids, heat transfer, and mixtures & solutions. Concepts introduced include globules, Kinetic Molecular Theory, kinetic energy, solids, liquids, gases, density, miscible, homogeneous mixture, immiscible, phase, biphasic mixture, multiphasic mixture, contracts and convection current. 
  • Before reading this article, teachers could have students complete a Vocabulary Preview learning strategy to engage prior learning and introduce new terminology. Ready-to-use Vocabulary Preview reproducibles for this article are available in [Google doc] and [PDF] formats. 
  • To consolidate understanding after reading the article, teachers could have students complete a Concept Definition Web learning strategy for the concept of Kinetic Molecular Theory. Ready-to-use Concept Definition Web reproducibles for this article are available in [Google doc] and [PDF] formats. 
  • To consolidate an understanding of different types of mixtures, teachers could have students create a graphic organizer, like a T-chart, to compare and contrast heterogeneous and homogeneous mixtures.
  • To further explore miscible and immiscible mixtures, teachers could have students do the hands-on activity What happens when we mix liquids? (Hands-on Activities). 
  • There are various applications of mixtures that could be used for cross-curricular art projects as well. For example, wax resist art and paper marbling.

Learn more

Chemistry for Kids: Chemical Mixtures (2019)
A plain-language, illustrated description of mixtures, including the difference between a solution and mixture.

The Kinetic Molecular Theory (2016)
A video (1:30 min) Scámarca Productions describing the theory. Based on an old junior high school assignment by the filmmaker!

How Liquid Motion Lava Lamps Work (2019)
A How Stuff Works description of lava lamps, including their history. 

How Do They Make Lava Lamps? (2016)
A video(3:02 min.) from Science Channel giving a behind-the-scenes look at how commercial lava lamps are made.

What is immiscibility? (2019)
A Let’s Talk Science Hands-on Activity.

Why do oil and water not mix? (2019)
A Let’s Talk Science Hands-on Activity.

References

Lumen Learning. (n.d.). Kinetic Molecular Theory of Matter.

Maggie's Science Connection. (n.d.). How a lava lamp works.

McVean, A. (2018, July 19). The Luminescent Chemistry of Lava Lamps. McGill University.

Scamarca Productions. (2016, May 24). The Kinetic Molecular Theory (Animation).