The water cycle is the constant cycle of evaporation, condensation and precipitation that controls the world's supply of water. Students learning about this cycle in middle school may have difficulty grasping that all the water we drink and use daily is recycled and has been used by someone before them. Giving students some simple modeling and science projects can help them grasp the concept more clearly.

Have students construct a 3-dimensional model of the water cycle using any materials they wish. Recycled materials, such as plastic grocery bags, or materials from around the house, like cotton balls, are ideal to help teach conservation as well as the water cycle. The model can be diorama-style and constructed in a shoebox, or it can be more involved and include scale models. Once the model is finished, have students show off their models and explain how each portion of the water cycle works.

Each student should imagine he or she is a drop of water. Using notebook paper or a computer, the student should write a creative short story about his journey through the water cycle. The student's "journey" can start at any point of the water cycle, as long as the entire cycle is completed by the end of the story. While the story can be creative and include embellished details, the parts of the water cycle should remain factual. If the student wishes, she can include illustrations and turn the story into a book.

Give each student a small paper cup and a plastic sandwich bag. Have the students put a small amount of water into the cup, roughly 3 centimeters. Once filled, the cup should be sealed into the sandwich bag carefully and placed on a sunny windowsill. Students should check their baggies at least once per day and record any changes in the bag in a notebook. Have students continue to observe the baggies daily for at least one week.

Give each student a plastic two-liter soda bottle cut in half. Have them fill the bottom half with potting soil and a few seeds for a small plant, such as beans or marigolds. Tell them to thoroughly water the seeds. Once the seeds have been watered, have them push the top halves down onto the bottom halves, creating a domed enclosure. Place the terrariums on a sunny windowsill. Have students observe their terrariums at least once daily over a period of a few weeks, noting any changes in a notebook. These changes can include water droplets gathered on the top half or a sprouting seed.