Week 15 - Introduction, Heat, Heating Technology and Thermal Energy

Exercise 1.4

Excercise 1.4
ACTIVITY A: Making your own Water Cycle!

If you have ever wondered why the bottoms of cumulus clouds are flat? It is because that is the altitude in the rising air where the gaseous water vapour changes back to liquid water droplets.
The change of state diagram can be used to describe the physical changes that all substances can go through. But, if we were to change the title of the diagram to the water cycle, it would still be correct.

The water cycle plays a very large part in ecosystems world wide. The world's weather is, in large part, caused by the uneven heating of the Earth's surface. The change of water to a gas (water vapour) is caused by the energy of the sun. But as the water vapour is carried upward by warm rising air, or over colder areas of the planet, it looses some of its energy and returns to very small droplets of liquid water and forms the clouds in the sky. The water cycle may cover huge areas of the Earth. For example, the sun may evaporate the water from the surface of the Pacific ocean. The wind then carries that water vapour for thousands of kilometres before it condenses into liquid water in the form of cloud droplets or even snow (solid water) over the Rocky mountains. Warm summer days in the mountains can melt and even evaporate some of the water collected there, to begin a new journey. The water molecules aren't destroyed, they only change state.

In fact some of the water in you right now might have been in a T-Rex or Cleopatra or a large redwood tree. The water we drink in has been in millions of places and probably thousands of organisms.

Build your Own Terrarium


  • A very large jar with screw-on lid
  • Some small stones
  • Sand if you have it
  • A small plant or two of any type
  • Some damp (slightly moist )potting soil
  • Finally you will need a shell, a large bottle cap, or a small lid filled with water


1. Layer the jar first with about 2cm of stones
2. Cover this with sand and then add potting soil to about half to a third of the jar.
3. Add your plants; making sure that the roots are in the soil.
4. Fill the small container with water. It will act as your lake in your artificial environment.
5. Finally, screw on the jar lid. You have now made a terrarium!

Now keep the terrarium in a shady spot for a few days and observe what happens.

Exercise 1.3: Make your own Water Cycle