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← Water, Water, Everywhere

Water cycle in a bag!

The whole water cycle, in a plastic bag taped to a sunny window. Students watch evaporation and condensation happen over a single day.

How it is taught

Set one bag up before the class as a demonstration, or let each group build its own.

What you need

  • A zip-lock bag of about a litre, water, tape, a permanent marker, and blue food colour if you have it
  • Water, enough to fill the bag to the line you draw
  • Tape, to fix the bag to the glass
  • A permanent marker
  • Blue food colour, optional — it makes the drops easier to see

The words

Water cycle

The manual states these. What it does not state is not here.

How it runs

The teaching sequence as the manual gives it.

  1. 01

    On the flat of the bag, draw a line across the middle for the surface of the water, land and sea below it, and a sun above. Press lightly with the marker so the bag does not tear.

  2. 02

    Fill the bag with water up to the line you drew. Add a drop of blue colour if you have it.

  3. 03

    Seal the bag properly and tape the top shut. Turn it over once to check it does not leak.

  4. 04

    Tape it to the inside of a window that gets direct sun. Make sure it is stuck firmly and cannot fall.

Talking about it

Discussion points, worked examples and the handouts the manual prints with this session.

Points for discussion

Say what should happen, then let the class watch the bag and describe what it actually sees. Come back to it after an hour, and again at the end of the day.

  • Water takes in heat and gives it off, and that is what moves it between liquid, vapour and ice.
  • The first thing to appear is drops on the inside of the bag, above the water line. Water left the surface as vapour and turned back to liquid on the cooler plastic. That is evaporation and condensation, in order.
  • When the drops grow heavy they run back down. Ask the class what that is in the real world, and where the sun comes into it.
More from the manual
  • Work alone or in groups of two to four. Copy the table below and fill it in, using this theme's background reading and the A to Z to work out what each word means.
  • When the table is done, compare it with somebody else's and see what they put.

Three columns: the process · have I seen it with my own eyes? · what it looks like where I live.

Surface water flow · yes · the river, or the nala behind the colony

Precipitation · yes · the last time it rained

Condensation

Evaporation

Groundwater flow

Filtration

Run-off

Where this comes from

Bridge the Gap is a compilation. This is what the manual records for this session.

The manual prints no source for this session. It is published here as Swechha has used it, adapted over years of classroom work; if you recognise its origin, tell us and we will credit it.

Before you start sets out where the compendium as a whole comes from.

Next

Where to go from here.

Next session

My Water FootprintWater, Water, Everywhere, 3 of 8

The theme

Water, Water, Everywhere8 sessions and the background reading

All eight themes

Teach43 sessions across 8 themes

Understand the data

The whole library · the A to Z