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Watering Down a Colour
Age 15 · Chemistry
The same amount of blue dye is spread through more and more water as you move along the rack. Because the dye is stretched over a larger volume, each tube looks paler than the one before it.
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Age 15: open this week
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In the picture
- The deep ink-blue tube at the left end of the rack
- The pipette with a droplet at its tip
- The clear, almost colourless tube at the right end of the rack
- The graduated cylinder of water with millilitre marks
Examples
- Adding water to fruit cordial until it turns from dark red to light pink
- Topping up strong black tea with hot water so it goes from near-black to light brown
Key takeaways
- Adding water raises the volume but keeps the amount of dye the same, so concentration drops.
- Colour depth is a quick visual clue to how concentrated a solution is.
Quiz: Watering Down a Colour (Age 15)
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Water is added to a coloured solution. Why does it look paler than before?
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One drop of the same dye is mixed into three tubes: tube A holds 10 mL of water, tube B holds 50 mL, and tube C holds 100 mL. Which tube looks palest?
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A pale solution is made by adding water to a dark one. Compared with the dark solution, the pale solution contains…
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