The best examples of 3 engaging examples of density experiments for kids

Starting with the best examples of 3 engaging examples of density experiments

Let’s skip the dry theory and jump straight into action. When teachers ask for the best examples of 3 engaging examples of density experiments, they usually want activities that:

• Use easy-to-find materials
• Work in a short class period
• Are dramatic enough to grab attention

Here are three core setups you can rely on again and again, plus several real examples of fun twists you can add.

Example of Experiment #1: The classic liquid density tower

If I had to pick just one activity to introduce density to kids, the liquid density tower would win every time. It’s colorful, dramatic, and almost impossible to forget.

You pour different liquids into a clear cup or cylinder and watch them stack in layers instead of mixing. Kids see that some liquids float on top of others because they’re less dense.

How it works in plain language
Density is how much “stuff” (mass) is packed into a certain amount of space (volume). A liquid with more mass in the same space is denser and sinks under a lighter liquid.

Materials you can use
You don’t need every item on this list, but having at least four or five makes a great tower:

• Honey or corn syrup
• Dish soap
• Water (you can color it with food coloring)
• Vegetable oil
• Rubbing alcohol (isopropyl alcohol, labeled clearly and supervised by adults)
• Lamp oil or baby oil

When you pour them slowly down the side of the container or over the back of a spoon, they settle into layers. Honey ends up on the bottom, oil near the top, and so on.

Real examples of extensions
Once the basic tower is built, you can turn it into a mini-lab:

• Drop in a small plastic bead, a grape, a paper clip, and a piece of candle wax. Ask students to predict where each object will “park” in the tower.
• Try warm water vs. cold water layers and talk about how temperature changes density. This connects nicely to ocean currents and climate discussions.
• Have students design a “mystery liquid” by mixing water and salt, then test where it fits in the tower.

For middle school and up, you can connect this to the formal density formula (density = mass/volume) and have students measure the mass and volume of each liquid before building their tower.

If you want a solid reference on density as a property of matter, the U.S. Department of Energy’s Office of Science has accessible explanations of states of matter and particle models: https://science.osti.gov

Example of Experiment #2: Sink-or-float with a twist (changing density)

A simple sink-or-float test is often one of the first examples of 3 engaging examples of density experiments teachers try. But the real magic happens when kids don’t just sort objects—they actually change density on purpose.

Real examples: From floating eggs to “magic” ketchup packets

Start with a basic question: Why does a raw egg sink in plain water but float in salty water?

Fill one clear cup with plain tap water and another with heavily salted water (stir until no more salt dissolves). Carefully place a raw egg in each. In most cases, the egg sinks in fresh water and floats in salt water because the salt water is denser than the egg.

Kids can then:

• Add more salt, a spoonful at a time, to see exactly when the egg begins to float.
• Try a hard-boiled egg and compare behavior.
• Use different brands of salt and talk (lightly) about impurities and crystal size.

Another student favorite is the ketchup packet in a bottle. Fill a clear plastic bottle with water and drop in a ketchup packet from a fast-food restaurant. Some packets float, some sink, and some hover in the middle because of tiny air bubbles inside. When you squeeze the bottle, the pressure compresses the air, increases the density of the packet, and makes it sink.

These are not just cute tricks—these examples include the same physics that help submarines control their depth using ballast tanks.

The U.S. Naval Academy and other educational sites often explain buoyancy and density in simple terms for students; a good starting point is the educator resources at https://www.navalacademy.edu (search their STEM outreach materials).

Example of Experiment #3: Hot vs. cold water density race

The third of our examples of 3 engaging examples of density experiments uses temperature to show how density changes. This one is ideal if you want to connect to weather, ocean currents, or climate science.

You’ll need two clear cups or jars, food coloring, and hot and cold water. Color one set of water red (for hot) and the other blue (for cold). Carefully place one cup on top of the other, using an index card as a temporary lid between them.

When hot water is on top and cold water is on the bottom, and you remove the card, the layers mostly stay separate because the warmer water is less dense and stays above the colder, denser water. If you flip the setup—cold on top, hot on bottom—the colors mix quickly as the denser cold water sinks.

Why this matters beyond the classroom
This is a small-scale model of how oceans and the atmosphere move. Warm water near the surface and cold, dense water below help drive global ocean circulation.

For teachers who want to go deeper into this, NASA’s climate education pages offer clear explanations and classroom-ready graphics: https://climate.nasa.gov

More real examples of engaging density experiments

Once you’ve tried those core setups, you can expand your toolkit. Here are more real examples of density experiments that build on the same ideas but keep kids curious.

Rainbow sugar water columns

This is a colorful spin on the liquid tower. Instead of different liquids, you use sugar solutions of different concentrations. More sugar dissolved in the same amount of water means more mass in the same volume—higher density.

Prepare several cups with water and dissolve different amounts of sugar in each (for example, 1 tablespoon, 2 tablespoons, 3 tablespoons, and so on). Color each solution a different color. Then carefully layer them in a tall clear glass. The heaviest sugar solution goes on the bottom.

This works beautifully as a math and science crossover because students can graph the relationship between sugar concentration and density.

Lava lamp in a cup

This is a favorite example of how gases, liquids, and density play together. Fill a clear cup mostly with vegetable oil, then add some colored water. The water sinks to the bottom because it’s denser than the oil. Drop in a piece of effervescent tablet (like Alka-Seltzer). Gas bubbles form, attach to the colored water, and carry blobs upward. When the gas escapes, the blobs sink again.

Students see that:

• Oil and water don’t mix because of polarity (great chemistry tie-in).
• Gas is less dense than liquid, so it rises.

The American Chemical Society’s “Chemistry in the Community" and “Middle School Chemistry” resources (https://www.acs.org) include similar activities and clear safety guidance for classroom chemistry.

Hot air balloon in a bottle (density of air)

Density isn’t just for liquids and solids—gases count too. Stretch a balloon over the mouth of a glass bottle. Place the bottle in hot water (not boiling, and supervised) and watch the balloon inflate as the air inside expands and becomes less dense. Move it to cold water, and the balloon shrinks as the air cools and becomes denser.

This is a simple example of how density differences in air create wind and weather patterns.

Layered fruit salad

You can even turn a snack into a set of density observations. Different fruits have different densities. Grapes, apple slices, orange segments, and banana pieces behave differently in water or juice. Have kids predict which fruits will float or sink, test their predictions, and then eat the results.

This is one of the best examples for younger kids because it feels like playtime, not a formal lab.

Using these examples of 3 engaging examples of density experiments across grade levels

One reason teachers keep asking for examples of 3 engaging examples of density experiments is that these activities scale up or down easily.

For younger students (grades K–3):

• Focus on the words “float” and “sink” and simple observations: “Which layer is on top? Which is on the bottom?”
• Keep materials safe and familiar—water, oil, fruits, and plastic toys.
• Use lots of color to highlight differences.

For upper elementary (grades 4–5):

• Introduce the idea that “heavier for its size” means denser.
• Have students record predictions and results in simple tables.
• Compare real examples, like ice floating in water vs. rocks sinking.

For middle school:

• Bring in the density formula and have students calculate density for different liquids or solids.
• Connect to real-world contexts: boat design, submarines, hot air balloons, and ocean currents.
• Ask students to design their own density experiment as a project.

The Next Generation Science Standards (NGSS), widely used in the U.S., highlight density as a way to talk about properties of matter and energy transfer. You can explore NGSS-aligned ideas at https://www.nextgenscience.org.

Safety tips when running density experiments

Even the best examples of 3 engaging examples of density experiments can go sideways if safety is ignored. A few friendly reminders:

• Label all containers clearly, especially if you’re using rubbing alcohol or other household chemicals.
• Avoid tasting any solutions, even if they look like juice.
• Use eye protection when working with glassware or anything that could splash.
• Have students wash hands after handling raw eggs or any chemical solutions.

For general lab safety practices appropriate for schools, the National Institutes of Health (NIH) and many university education departments provide guidelines; one helpful starting point is NIH’s science education resources at https://www.nih.gov/education-research.

FAQ: Common questions about examples of density experiments

What are some easy examples of density experiments I can do at home?

Easy examples include the floating egg in salt water, a simple oil-and-water bottle, and testing which fruits float or sink in a bowl of water. These use materials most families already have in the kitchen.

Can you give an example of a density experiment that works for a science fair?

A strong science fair project is a sugar-water density series where students change the amount of sugar, measure density, and then test how that affects the floating height of different objects. This example of a density experiment allows for real data collection, graphs, and analysis.

How do I explain density to younger kids without using formulas?

Use comparisons: “Imagine stuffing more and more socks into the same drawer. The drawer doesn’t get bigger, but it gets heavier. That’s like increasing density.” Then show real examples, like a small rock vs. a big sponge.

Are there examples of density experiments that connect to real life?

Yes. Real examples include boats floating because their overall density (including the air inside) is less than water, hot air balloons rising because warm air is less dense, and ocean layers forming because of temperature and salt differences. Your classroom liquid tower is a mini-version of those real systems.

How many examples of 3 engaging examples of density experiments do I actually need in a unit?

Most teachers find that three core activities—such as a liquid density tower, a sink-or-float with changing density, and a hot vs. cold water experiment—give students a strong foundation. From there, adding two or three more real examples (like sugar water rainbows or lava-lamp cups) keeps the unit fresh without overwhelming your schedule.

By building your lessons around these best examples of 3 engaging examples of density experiments, you’re not just checking off a standard—you’re giving kids a set of vivid mental pictures they’ll carry into every future science class. And honestly, watching their faces light up when the layers separate or the egg suddenly floats? That’s the part you’ll remember too.