The Water Cycle

As discussed in class, the water (or hydrologic) cycle is vital to life on Earth. In this activity you will be investigating the essential parts of the cycle by building and operating a model. Because big, global-scale systems like the water cycle are difficult to study directly, scientists often use small-scale models to study them. Sometimes these models are physical models like you are using here, and sometimes they are computer simulation models.

Materials

• Artist's clay or plastic mountain model
  
  
• Plastic shoe box with cover
  
  
• Petri dish
  
  
• Lamp
  
  
• Water
  
  
• Crushed ice
  
  

Procedure

1. According to your teacher's instructions, form teams of three to five students. Each team will be given the materials listed above.
   
   
2. Using the clay, shape a mountain. Place the mountain inside the box against one side with the sloped side facing the interior of the box.
   
   
3. Pour water into the box until about one-fourth of the mountain slope is covered. The water forms your model ocean.
   
   
4. Replace the lid of the shoe box.
   
   
5. Place a petri dish on top of the shoe box over the mountain (as shown in the picture).
   
   
   
   
6. Place crushed ice into the petri dish.
   
   
7. Position the lamp over the ocean. Turn on the lamp. CAUTION: THE LAMP WILL GET HOT. DO NOT TOUCH THE BULB OR SHADE.
   
   
8. Observe the container carefully and note any changes that you see. If instructed by your teacher, you may want to see if you can detect any air circulation in the box, by lighting 2-3 matches, blowing them out and quickly dropping them onto the model mountain. The smoke they give off should move with the air movement.

Observations and Questions

Answer these in your notebooks or on a separate piece of paper.

1. Which part of the activity simulated evaporation?
   
   
2. Which part simulated condensation?
   
   
3. Which part simulated precipitation?
   
   
4. What is the energy source and what does it represent?
   
   
5. What elements of the water cycle are not represented?
   
   
6. How could we demonstrate transpiration in this activity?
   
   
7. Would condensation occur in the box without the ice? Why or why not?
   
   
8. After observing this activity, explain why water is considered a renewable resource.
   
   
9. The system you observed/constructed is a model of the way the actual water cycle works. Why might scientists use a model like this in their research into the water cycle in the real world? Can you think of any reason that using such models might be a problem?
   

When you're finished with the activity, click on Back to Teacher Guide at the top of the page.