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← Investigators ScienceDensity of liquids25 minutesStd 6–8

Density Tower

✨ Four kitchen liquids sit in four separate stripes in one glass, and a grape parks itself halfway down.

A tall glass with four labelled liquid layers, honey at the bottom then washing-up liquid, water and oil, with a bottle cap resting on the water and a grape resting on the washing-up liquid, beside the rule density equals mass divided by volume.
How it works

🧰 You need

  • a tall clear glass
  • honey
  • washing-up liquid
  • coloured water
  • cooking oil
  • a grape and a plastic bottle cap

👀 What you will see

The liquids stay in four stripes with honey at the bottom and oil on top. The grape sinks through the oil and water but stops on the washing-up liquid. The bottle cap floats higher, resting on the water.

🧪 Do it

  1. Pour honey into the middle of the glass so it does not touch the sides.
  2. Tilt the glass and pour washing-up liquid slowly down the inside wall.
  3. Add coloured water the same slow way, then cooking oil on top.
  4. Let the glass stand for two minutes and measure the height of each layer.
  5. Drop in a grape and then a bottle cap and note where each one settles.
  6. Weigh fifty millilitres of each liquid on a kitchen scale and write the masses down.

💡 Why it happens

Density is how much mass is packed into each unit of volume, found by dividing mass by volume. Liquids that do not mix settle with the densest at the bottom, so your stripes are in order of density: honey about 1.4 grams per cubic centimetre, washing-up liquid about 1.03, water 1.00 and oil about 0.92. Each object sinks until it reaches the first liquid that is denser than itself, and then floats there. Pouring slowly down the wall matters only because it avoids mixing, not because it changes any density.

🔁 Now try this

Calculate the density of each liquid from your fifty-millilitre masses and check that the calculated order matches the order in the glass.

🤔 Think about it

Why does spilled oil spread across the surface of the sea instead of sinking out of sight?

🧘 Ask the Acharya

“Why does spilled oil spread across the surface of the sea instead of sinking out of sight?” — ask him and he will explain it from your own chapters.

Ask Guru →

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