Today is rung 3 of 5 on this topic
Earth's systems and the water cycle
Can do: Explains how the water cycle moves water between spheres, and where fresh water actually is.
Why it matters
It links physical processes to a real resource problem, and the numbers involved are genuinely surprising.
What it looks like when it's wobbly
Recites evaporation-condensation-precipitation as a memorised loop without understanding what drives it.
⏱️ Two-minute check
"What makes water evaporate? What percentage of Earth's water do you think we can drink?"
Solid looks like: Heat from the sun, and some awareness that drinkable water is a tiny fraction.
The full activity for this topic · 15 minutes to set up, days to watch
Water Cycle in a Bag
- 1Put coloured water in the bag, seal it, tape it to a sunny window.
- 2Watch over hours and days as it evaporates, condenses and runs back down.
- 3Ask where the energy driving it comes from.
- 4Do the 100 ml demonstration: of all Earth's water, about 3 ml is accessible fresh water.
- 5Audit household water use for one day and estimate the daily total.
If it's too hard
The bag and the observation only.
If it's too easy
Explain how the same cycle causes both droughts and floods, and what humans change about it.
Say this
"What's actually pushing the water up into the air? Nothing moves for free."