Key Concepts
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Chemistry -
Molecules -
Buoyancy -
Density -
Polarity
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Introduction
Have you ever seen a lava lamp? They might look complicated, but you can make your own using common kitchen supplies. Try this activity to find out how!
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Background
If you look around your kitchen, there are probably a lot of different liquids, including water, juice, milk and oil. Many of these liquids have different properties that you can see, feel and taste. For example, milk is opaque and white whereas water is transparent and clear, and oil has a “slimy” texture that makes it difficult to clean if you spill it.
Each liquid also has other properties that might not be so obvious because you can’t “see” them easily. For example, they all have different densities (the amount of mass per unit of volume). Many common household liquids such as juice and milk have a density very close to that of water, so you might not notice a difference. Oil, however, has a lower density than water, meaning it can float on top of water. (It is buoyant.) You can see this if you try putting a few drops of oil in a glass of water—they will float on the surface.
Liquids are all made up of molecules that have different chemical properties. Some molecules are polar, meaning they have unbalanced electrical charges. These molecules tend to mix with one another better than they mix with nonpolar molecules, which have evenly distributed charges. You can observe this if you try mixing different liquids together. For example, it’s very easy to mix together juice and milk or water and food coloring. But if you try mixing water and oil—even if you stir vigorously—the liquids “want” to stay separated.
What can you do with all this information? In this project you’ll use it to make your own lava lamp!
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- An adult helper
- Clear glass
- Tap water
- Vegetable or mineral oil
- Food coloring
- Alka–Seltzer tablets
- Flashlight (optional)
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Preparation
Prepare a work area where you can easily clean up any spills, such as a kitchen counter.
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Procedure
- Fill your glass about one quarter full of water.
- Add several drops of food coloring.
- Fill the rest of the glass with oil (not all the way to the brim).
- Break an Alka–Seltzer tablet into four roughly equal-size pieces.
- Drop one of the pieces into the glass. What happens?
- Wait for the bubbles to stop, then drop in another piece. How long do the bubbles last for each piece?
- Extra: Stand a large flashlight on its end, with the light facing up, and place the glass on top. Turn off the lights in the room and turn the flashlight on. Drop in another Alka–Seltzer tablet, and you’ve made a lava lamp!
- Extra: Try the activity with different temperatures of water. How does water temperature affect your results?
- Extra: Try using half a tablet or even a whole tablet at once. What happens?
- Extra: Try pouring some salt into your glass instead of using an Alka–Seltzer tablet. What happens?
- Extra: Try reversing the order in which you add substances to the glass. What happens if you pour the oil in first, then add the water and food coloring?
- Extra: Review the information in the “background” section. Try making a lava lamp with different liquids you can find in your kitchen. What combinations of liquids work, and which ones don't? Can you figure out why?
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Observations and Results
When you pour the oil into the glass you should see it does not mix with the water—it forms a separate, clear layer on top. This occurs for two reasons: First, the oil and water are different densities—the oil is lighter, so it stays on top. Second, the water (and food coloring) molecules are polar, so they are strongly attracted to one another. The oil molecules are not polar, so they don’t mix with the water or the food coloring. This is why you’ll get the same result no matter what order you pour substances into the glass—the water and food coloring will always sink to the bottom instead of mixing with the oil.
When you drop an Alka–Seltzer tablet into the glass, it sinks to the bottom. It sinks straight through the oil without any chemical reactions occurring. When it touches the water, however, a chemical reaction occurs that releases carbon dioxide gas bubbles. These bubbles are less dense than the water or the oil, so they float to the top—but they “stick” to the water a bit, dragging some water droplets up toward the surface with them. When they reach the surface, the gas bubbles pop and the water droplets sink back to the bottom—creating a lava lamp effect.Eventually the Alka–Seltzer tablet will be completely consumed, and the chemical reaction will stop. If you let the glass sit still, all the water droplets will sink back to the bottom. (Remember, they don't want to mix with the oil.) But as long as you have more tablets, you can keep the reaction going!
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Cleanup
Do not pour all that oil down the drain! It could cause a serious clog. Ask an adult for help disposing of it. Options may include putting it in a sealed container in the trash or pouring it outside.
If necessary, use towels to clean up any spilled water or oil.
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Safety First & Adult Supervision
- Follow the experiment’s instructions carefully.
- A responsible adult should assist with each experiment.
- While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
- Adults should handle or assist with potentially harmful materials or sharp objects.
- Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.
Next Generation Science Standard (NGSS) Supported - Disciplinary Core Ideas
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.
Physical Science (PS)1: Matter and Its Interactions
Grades K-2
- 2-PS1-1. Different kinds of matter exist and many of them can be either solid or liquid depending on temperature. Matter can be described and classified by its observable properties.
- 2-PS1-2. Different properties are suited to different purposes.
Grades 3-5
- 5-PS1-1. Matter of any type can be subdivided into particles that are too small to see, but even then, the matter still exists and can be detected by other means.
- 5-PS1-2. The amount (weight) of matter is conserved when it changes form, even in transitions in which it seems to vanish.
- 5-PS1-3. Measurements of a variety of properties can be used to identify materials.
Grades 6-8
- MS-PS1-1.
- Substances are made from different types of atoms, which combine with one another in various ways.
- Atoms form molecules that range in size from two to thousands of atoms.
- MS-PS1-2, 3.
- Each pure substance has characteristic physical and chemical properties that can be used to identify it.
- MS-PS1-4.
- Gases and liquids are made of molecules or inert atoms that are moving about relative to each other.
- In a liquid, the molecules are constantly in contact with others.
Grades 9-12
- HS-PS1-1. Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.
- HS-PS1-2. The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.
- HS-PS1-3. The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms.
- HS-PS1-4. Stable forms of matter are those in which the electric and magnetic field energy is minimized. A stable molecule has less energy than the same set of atoms separated; one must provide at least this energy in order to take the molecule apart.
Grades K-2
- 2-PS1-4. Heating or cooling a substance may cause changes that can be observed. Sometimes these changes are reversible, and sometimes they are not.
Grades 3-5
- 5-PS1-4. When two or more different substances are mixed. A new substance with different properties may be formed.
- 5-PS1-2. No matter what reaction or change in properties occurs, the total weight of the substances does not change.
Grades 6-8
- MS-PS1-2. Substances react chemically in characteristic ways.
- MS-PS1-3. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.
- MS-PS1-5. The total number of each type of atom is conserved, and thus the mass does not change.
- MS-PS1-6. Some chemical reactions release energy, others store energy.
Grades 9-12
- HS-PS1-4,5. Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangement of atoms into new molecules with consequent changes in the sum of all bond energies in the set of molecules that are matched b the changes in kinetic energy.
- HS-PS1-6. In many situations, a dynamic and condition-dependent balance between a reaction and the reverse reaction determines the numbers of all types of molecules present.
- HS-PS1-7. The fact that atoms are conserved, together with the knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.
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