The Water Cycle

Activities to try

1. 1

   Sun-driven water-cycle model the learner controls

   Why it works: The water cycle is an endless loop driven by the Sun's energy, and the same water is conserved — it only changes form (liquid↔invisible vapour) and place, never being used up or destroyed.

   1. Over a land-and-sea scene, raise a Sun/heat control and watch puddles and sea surfaces give off vapour that rises, cools into clouds, and falls as rain that flows back to the sea.
   2. Turn the Sun control down and observe the whole loop slow: evaporation slows, fewer clouds form, and rain becomes less — stating in your own words why.
   3. Switch to a 'follow one droplet' view: tag a single glowing droplet and watch it evaporate, become near-invisible vapour, condense inside a cloud, fall as rain, and flow back to the start again — never disappearing.
   4. Watch a drying puddle on a hard surface and describe out loud where the water goes (UP into the air as invisible vapour), rather than saying it just vanished. (On soil, some puddle water also soaks into the ground.)
2. 2

   Drying puddle and cold-can discrepant-event investigation

   Why it works: Evaporated water becomes invisible vapour in the air (it doesn't vanish), and 'sweating' on a cold surface is water condensing FROM the surrounding air, not water seeping through the container.

   1. Before observing a puddle (or a shallow dish of water) left in a warm, sunny spot, predict and write down what will happen to the water and WHY.
   2. Watch over time as it dries, then explain where the water went — into the air as invisible vapour. (Water in a dish cannot soak away, so it can only have gone into the air; a puddle on soil or grass can also lose some water by soaking into the ground.)
   3. Add a few drops of food colouring to ice water in a can or cup, then watch for droplets forming on the OUTSIDE of the cold surface and check their colour.
   4. Explain why any outside droplets are CLEAR, not coloured: the water condensed from the air onto the cold surface — it did not leak through the wall.
3. 3

   Fair test: does temperature change how fast water evaporates?

   Why it works: Under matched conditions, warmer water evaporates faster, so the rate of evaporation rises with temperature. In everyday life a hot day speeds drying, and on a sunny day both the warmth and the direct sunlight raise the rate — the Sun's heat is what warms water and drives the cycle.

   1. Fill two similar open dishes with the same amount of water — one with warm water and one with cool water — keeping dish size, surface area, air flow and location the same so that only the water temperature differs.
   2. Predict which will lose water faster and why.
   3. Check them over time (e.g. mark or measure the water level) and compare which lost water faster, remembering that the warm water slowly cools towards room temperature, so the difference may be small and is clearest early on.
   4. State your conclusion from what you observed: if the warmer dish lost more water, this supports the idea that higher temperature increases the rate of evaporation.
   5. As a separate question about the Sun's role, compare a puddle in the sun with one in the shade (observing the puddles on the ground) and discuss which dries faster and why — remembering the puddles may also differ in size and depth.