For this experiment, you need one large bowl, a smaller bowl, plastic wrap and a small stone or other small weight. Place water in the large bowl and sit the small bowl on top of the water. Firmly secure the plastic wrap over the top of the large bowl, and place the weight in the middle of the plastic wrap. The water in the large bowl will turn to vapor, condense on the plastic, and eventually drip down into the small bowl, simulating phase changes of water and how it circulates within the environment.
This experiment uses evaporation and condensation to approximate the role of rain and clouds in the cycle. Take a glass jar with a metal lid, and pour about one or two inches of hot water in the bottom. Place the lid upside-down on top of the jar, and put several ice cubes on the jar lid. Instruct the students to observe the process and note their observations. Water droplets will accumulate on the bottom of the lid, simulating the interchange of water between lakes and rivers and "clouds" above.
Take an empty 2-liter plastic bottle and place a temperature strip inside. Screw on the cap and measure the temperature. Then squeeze the bottle as hard as possible for one minute. Have the students note the effect on temperature, which will increase due to the increase in pressure inside. Then open it and pour in a bit of water. Light a match, extinguish it, and toss the match in the bottle. Immediately fasten the cap and squeeze the bottle as before. The effect of heat and pressure should produce an evaporative effect that creates a cloud (actually just water vapor) inside. Use the experiment to discuss what role clouds, fog and other phenomena play in the water cycle.
This experiment adds soil and plants to simulate the earth's surface. In a terrarium, plant seeds (such as marigold seeds) in soil. Water the soil, and tightly secure the terrarium lid. Then place the whole thing in direct sunlight. Instruct students to examine how water changes from liquid to gas as it cycles through the "world" of the terrarium.