ERN Item Type:
- Classroom Activities
Carry out a laboratory demonstration of the first stages in the chemical weathering of limestone. Quarter-fill a small glass beaker or a boiling tube, with some water of neutral pH and add some Universal indicator. Ask what will happen if a pupil blows steadily into the water through a straw (it pays to choose the most talkative pupil to do this!). Watch what happens as the exhaling continues, and see if the water will turn acid – indicated by the colour changing from green to yellow, to orange or even to pink. Ask pupils to explain why this has happened.