Materials You Need
Food colouring (Red, Yellow, Purple, Blue)
Prepare the materials required.
Add increasing amount of sugar to the cups based on the number of spoonful indicated in the video.
Pour warm water into the cups of sugar until they are ¼ full.
Stir well to allow the sugar to dissolve in the water.
Add food colouring to the respective cups. (Note: Coloured water with the least sugar will appear at the top of the rainbow in the cup.)
Slowly pour in the coloured water starting from the cup with the most amount of sugar. You may use the side of the cup to slowly pour the water.
Continue to add the coloured water from the most to the least amount of sugar.
After all the layers of coloured water are added, you get a rainbow in a cup!
What is the science behind this?
Density refers to the mass of an object in a given volume. Different objects have different densities.
Based on the above formula, with a fixed volume, the density increases when the mass increases. Therefore, with more sugar added to a fixed volume of water in each cup, the coloured water becomes denser.
To form a rainbow in the cup, the colours are layered on top of each other according to the density of the water. The bottom of the cup contains coloured water with the most sugar which has the highest density, hence it sinks to the bottom. As we move up the cup, the density of the layers of coloured water decreases, causing them to float on top of each other.
When an object is placed in water, it floats when it is less dense, whereas it sinks when it is denser.
Using this principle of density, we have created a rainbow in a cup!
Try this too!
Create your rainbow using different liquids such as oil and dishwashing soap and compare their densities!
Need more practice?
Check out the relevant practice books at the major book stores!
- Perfect Guide Lower Sec Science MCQ & Free Response Questions Book A
(click here to purchase online!)
- Perfect Guide Lower Sec Science MCQ & Free Response Questions Book B
- Perfect Guide Lower Sec Science Structured Questions Book A
- Perfect Guide Lower Sec Science Structured Questions Book B
Read Also: How Can You Help Your Child with Home-based Learning?
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