Geography GCSE: What causes rain?
Scientists investigate how the rain cycle works by looking into the formation of raindrops in clouds which causes them to fall.
Microbiologist Chris Van Tulleken looks into the possibility of raindrops being seeded by bacteria by setting up an experiment.
He tests different types of water to see which one will freeze quicker: pure water, water with mineral dust in it or water containing bacteria found in clouds.
As the temperature drops, it is clear that the bacteria-containing water freezes first, followed by that containing mineral dust. This leads to weather forecasters being able to predict rain based on the bacteria content of clouds.
This clip is from the series Operation Cloud Lab: Secrets of the Skies.
Could be used as an introduction to a How Science Works Investigation.
The class could be shown this clip and then asked to identify: The Hypothesis, the variables (independent, dependent, control), any safety precautions and whether the results support the hypothesis.
This clip is suitable for teaching Geography at GCSE in England and National 4 in Scotland. Appears in AQA, OCR, EDEXCEL, CCEA, WJEC, SQA.