Obtaining pure water from water dyed with food-colouring

Suitability Level: P5

Topic: Water and Changes of State

Concepts: Evaporation and Condensation

Apparatus Needed:

(1) Beaker filled with 100ml of hot water

(2) Food-colouring dye

(3) Stirrer

(4) Evaporating dish

Procedure:

(1) Put a drop of food-colouring dye into the beaker of hot water.

(2) Stir the beaker of hot water with the dye.

(3) Cover the mouth of the beaker with the evaporating dish.

(4) Observe what is collected on the underside of the dish after a short while.

Explanation:

The water in the beaker evaporated into warm water vapour, which comes into contact with the cooler, underside of the evaporating dish, loses heat quickly and condenses into water droplets, leaving behind the coloured dye in the beaker.

Application of concepts learnt to our everyday life:

1. The water droplets observed representsthe clouds we see in the sky.
2. The evaporating dish represents the cooler surrounding air in the atmosphere.
3. The beaker of water represents water bodies such as seas and oceans.