Rainbow Density Tower Experiment: Liquid Stratification
- Time
- 20-30 min
- Difficulty
- Easy
- Best for
- Class 6-8
- Subject
- Chemistry
- Things needed
- 8, all at home
- Steps
- 11
- Cost
- Free, nothing to buy
- You will learn
- Density and Liquid Stratification
What you need
0 of 8 readyTap each thing once you have it in front of you. Items with the house sign are already somewhere in your home.
- 🏠 Honey or thick sugar syrup (chashni) 50 ml No luck? Use thick sugar syrup made by boiling 4 tbsp sugar in 2 tbsp water.
- 🏠 Liquid dishwash soap (Vim or Pril) 50 ml No luck? Use concentrated liquid detergent.
- 🏠 Water 100 ml
- 🏠 Cooking oil (Sunflower or Mustard oil) 50 ml No luck? Use coconut oil or baby oil.
- 🏠 Surgical spirit or Rubbing alcohol 50 ml No luck? Use sanitizer gel mixed with a few drops of water, or omit layer.
- 🏠 Clear narrow glass or plastic bottle 1 container No luck? Use empty transparent 500 ml water bottle cut at top.
- 🏠 Food colors or fountain pen ink 2-3 drops of 3 colors No luck? Use turmeric powder for yellow, Kumkum for red, blue fountain pen ink.
- 🏠 Spoon or plastic dropper 1 piece No luck? Use plastic straw held at top with finger.
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.
Saved on this device- Rubbing alcohol (isopropyl alcohol) is flammable and can cause mild skin or eye irritation.
- Glassware carries a breakable hazard.
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 a tall, clear plastic container or glass jar upright on a flat work surface.Handle glass containers gently to prevent accidental breakage.
- Pour 50 ml of honey or thick sugar syrup directly into the center of the container bottom.
- Add two drops of blue food coloring into 50 ml of liquid dish soap in a small cup.
- Pour the colored dish soap slowly over the center of the honey layer.
- Mix two drops of red food coloring into 50 ml of tap water in a separate cup.
- Tilt the container slightly and trickle the red water down the inside wall using a spoon or plastic dropper.
- Pour 50 ml of cooking oil gently along the tilted inner wall so it floats on top of the water.
- Mix a drop of yellow food coloring into 50 ml of rubbing alcohol in a separate cup.Avoid direct skin or eye contact with rubbing alcohol, and keep it away from open flames.
- Trickle the colored rubbing alcohol very slowly down the side of the container to form the uppermost layer.Ensure the work space is well-ventilated while using rubbing alcohol.
- Set the container upright on your flat surface and allow the liquids to settle for three minutes.
- Observe how each liquid remains in a distinct colored layer from densest at the bottom to least dense at the top.
The Concept
You can stack liquids on top of one another without mixing them if each liquid has a different density. This experiment demonstrates how mass and volume determine liquid layers.
Observation
When you carefully pour different colored liquids into a tall glass cylinder, they do not mix together into a muddy brown mess. Instead, they stack neatly on top of each other like a vibrant, liquid rainbow.
Heavy liquids like honey or corn syrup sit right at the bottom. Dish soap forms a clear layer above them, followed by water, vegetable oil, and finally rubbing alcohol floating right at the top. Each layer stays completely separate, creating sharp, colorful boundaries between the different liquids.
Why It Happens
It all comes down to a property called density. Density tells us how tightly matter is packed inside a specific amount of space.
Think of it like two identical school backpacks. If you fill one backpack completely with heavy textbooks, it becomes very dense and heavy. If you fill the second identical backpack with soft sponges, it remains light and less dense. Even though both backpacks take up the exact same amount of space, the textbook bag has much more mass packed inside it.
In your rainbow tower, liquids with more mass crammed into every drop (like honey) are denser and sink to the bottom. Liquids with less mass packed into the same space (like oil or alcohol) are less dense, so they float effortlessly on top.
The Science Behind It
In scientific terms, density is defined as mass per unit volume (Density = Mass / Volume). Every pure substance or solution has its own unique density based on its molecular structure and how closely its molecules sit together.
This experiment connects directly to your NCERT topic on Is Matter Around Us Pure? where we study heterogeneous mixtures and immiscible liquids. Liquids like oil and water are immiscible, meaning they cannot dissolve into one another. Because they do not mix, their density differences allow them to separate cleanly into different layers, or phases.
Additionally, when you make a sugar solution for this tower, adding more sugar increases the total mass of the liquid without changing its volume by much. This increases the solution's concentration and density, proving that solution strength directly changes how liquids behave when stacked.
Make It a Project
Turn this demonstration into a full science fair project by testing how changing variables alters stratification:
- Independent Variable: Concentration of solute (e.g., grams of salt or sugar dissolved per 100 mL of water) or type of liquid used.
- Dependent Variable: Layer position (order of stratification from bottom to top) and layer stability over time.
- Control Variables: Volume of each liquid layer, temperature of liquids, container diameter, and pouring speed.
Data to Record: Measure mass and volume for each liquid to calculate density in g/mL. Record the time taken for layers to settle and track visual sharpness after 1, 12, and 24 hours.
Presentation Tip: Display your tower clearly illuminated from behind using a torch or light box. Add a line graph plotting Solute Concentration (g/100 mL) versus Calculated Density (g/mL).
FAQs
Why do the liquids not mix when you pour them together?
Liquids with different densities naturally separate. Denser liquids sit lower, while lighter liquids float above. Also, immiscible liquids like oil and water cannot dissolve into each other. If you pour them gently along the glass wall, their surfaces stay intact and distinct layers form.
What happens if you shake or stir the density tower?
Shaking the tower forces the layers to mix temporarily. Liquids that dissolve in each other, like water, alcohol, and food coloring, will blend permanently. Oil and water will separate back into distinct layers after standing for a few minutes because they are completely immiscible.
Can you make a density tower using only water and sugar?
Yes, you can create a tower using only water, food coloring, and different amounts of dissolved sugar. Adding more sugar increases the mass of the water without changing its volume much. This creates dense sugar water that sinks beneath lighter, less concentrated colored water.
Why does vegetable oil float on top of colored water?
Vegetable oil floats because it is less dense than water. A cup of water carries more mass than a cup of oil. Additionally, oil is non-polar and water is polar, which means they are immiscible and cannot dissolve into one another.
What happens if you drop a small solid object into the tower?
The solid object sinks until it reaches a liquid layer that is denser than itself. A metal bolt drops straight to the bottom because it is denser than honey. A plastic die floats on the soap layer, while a grape stops at the syrup layer.
Your lab notebook
Two minutes here and your lab record is done. Everything stays on this device until you copy it out.
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