DIY Lava Lamp Experiment: Density and Polarity

Water is denser than oil, so it sinks below the oil layer. Because polar water and non-polar oil cannot mix, an effervescent tablet generates gas bubbles that float colored water upward until the bubbles burst and the droplets sink.

Easy ⏱ 15 min 🔭 Class 6-8 🏠 4 of 5 things are at home 🧑‍🔬 Do it with an adult

Time: 15 min
Difficulty: Easy
Best for: Class 6-8
Subject: Chemistry
Things needed: 5, 4 at home
Steps: 11
Cost: Low, a few things to find
You will learn: Liquid Density and Immiscibility

DIY Lava Lamp Experiment: Density and Polarity, Experiment · Class 6-8 | jijnas.com

Before you start

What you need

0 of 5 ready

Tap each thing once you have it in front of you. Items with the house sign are already somewhere in your home.

🏠 Clear glass jar or transparent plastic bottle 1 No luck? Use tall clear drinking glass.
🏠 Sunflower oil or any cooking oil 200-300 ml No luck? Use baby oil or mineral oil.
🏠 Water 100 ml
🏠 Food color or blue fountain pen ink 5-10 drops No luck? Use liquid turmeric water.
Eno sachet or effervescent tablet 1 sachet No luck? Use 1 tsp baking soda and 1 tbsp lemon juice.

💬 Send to a parent

Think first

What do you think will happen?

Real scientists guess before they look. Write one line now. After the steps, the page will show it next to what you should see.

Safety first, an adult should be with you.

Do not cap or seal the container while the effervescent tablet is reacting, as gas build-up creates a pressure hazard.
Effervescent tablets (e.g., Alka-Seltzer) contain medication and must not be ingested during the experiment.

Do it

The procedure

Tap a step when it is done. Lab mode shows one step at a time in big letters, reads it aloud if you want, and keeps the timer.

Place your clear glass jar on a flat, stable surface.
Pour cooking oil into the jar until it is roughly two-thirds full.
Add water to the jar, leaving a small space at the top.
Wait for the oil and water to separate completely into two layers.
Add 5 to 10 drops of food coloring into the container.
Watch the food coloring sink through the oil and mix into the bottom water layer.
Break one effervescent tablet into smaller fragments.Do not ingest effervescent tablets during the experiment, as they contain medicinal ingredients.
Drop a single piece of the tablet into the container.
Observe the colored water droplets float up through the oil layer and sink back down.
Add another piece of the tablet once the bubbling motion slows down.
Keep the jar completely open throughout the entire process.Never place a cap or lid on the container while it is bubbling, because gas build-up creates a hazardous pressure increase.

01 · The idea

The Concept

In this activity, you combine two liquids that refuse to mix: vegetable oil and water. Adding a bit of food coloring and a fizzy tablet turns a simple jar into a continuous, bubbling motion display.

02 · What you should see

Observation

You will observe two distinct layers in your container, with the oil floating calmly above the water. Drops of food coloring sink straight through the oil layer without dissolving, mixing only when they touch the water layer below.

When you drop an effervescent tablet inside, dynamic colorful bubbles rise through the oil layer to the surface. After the gas bubbles pop at the top, the heavy colored water droplets drop back to the bottom, creating a repeating lava lamp motion.

03 · Why it happens

Why It Happens

Oil and water do not mix, and water is naturally heavier (denser) than oil, so it sits at the bottom. The effervescent tablet reacts with the water to make fizzy gas bubbles.

Think of these carbon dioxide gas bubbles like tiny floaties or lifejackets attached to water droplets. The lightweight gas drags the water droplets up through the oil layer. When the bubble reaches the top, it pops and releases the gas into the air. Without its floating lifejacket, the heavy water droplet quickly sinks back to the bottom.

04 · The science

The Science Behind It

This activity demonstrates two fundamental concepts: polarity and density. Water molecules are polar, meaning they have positive and negative ends that cling tightly together. Oil molecules are non-polar and lack charge, making the two liquids immiscible (unable to dissolve into each other). Food coloring is water-based, so it only dissolves in the polar water layer.

In terms of density, water has more mass packed into the same space compared to oil, making it denser. As discussed in NCERT lessons on separating mixtures, immiscible liquids naturally separate into layers based on density. The tablet adds a dynamic gas phase, temporarily lowering the overall density of the water-gas combination and driving the continuous rise-and-fall cycle.

05 · Take it further

Make It a Project

Turn this simple demonstration into a complete science fair project by altering specific variables and recording your results.

Test temperature effects: Compare cold water, room temperature water, and warm water. Record how quickly the colored droplets rise and how long the bubbling lasts.
Vary the tablet size: Drop in quarter, half, and whole tablets to see how gas volume changes the speed of the rising droplets.
Change the top liquid: Try baby oil or mineral oil instead of vegetable oil to see if clarity or droplet speed improves.
Presentation tip: Place a small LED flashlight underneath your bottle during your demonstration to highlight the rising color blobs for your audience.

06 · Questions students ask

FAQs

Why does food coloring mix with water but not oil?

Food coloring is water-based and polar, just like water. Its charged molecules easily mix with water's charged molecules. Oil is non-polar and has no charge, so the polar color drops pass right through the oil without dissolving until they reach the water.

What happens if I use salt instead of an effervescent tablet?

Salt is denser than both oil and water. When you sprinkle salt, it sinks and drags a blob of oil down to the bottom with it. As the salt slowly dissolves in the water, the trapped oil breaks free and floats back to the surface.

Why does the water sink back down after reaching the top?

The gas bubble acts like a tiny floatie that carries the water droplet upward. Once it reaches the surface, the gas escapes into the air. Without the gas to hold it up, the dense water droplet falls back down through the lighter oil.

Can I reuse my DIY lava lamp after it stops bubbling?

Yes, you can reuse it repeatedly. The oil and water remain separated in your bottle. Whenever you want to restart the lava lamp effect, simply drop in another piece of an effervescent tablet to generate fresh gas bubbles.

What makes oil less dense than water?

Density depends on how closely packed a substance's molecules are. Water molecules pack tightly together, making water heavy for its size. Oil molecules are larger and spread farther apart, which makes oil lighter and allows it to float on water.

Write it up

Your lab notebook

Two minutes here and your lab record is done. Everything stays on this device until you copy it out.

Did it work?

What I actually saw What I would change next time

💼 Same science, as a real job

The physics or chemistry on this bench is what a working business charges for. See the numbers, the licences and the worst case before anyone spends a rupee.