Hobbies And Interests
Evaporation Rates
An outdoors experiment can illustrate the phenomenon of evaporation simply, while allowing kids an opportunity to hypothesize. Fill a pan or tray with a shallow layer of water and place it outside in the sun. Measure how long it takes for the water to fully evaporate. Next, place trays with equal amounts of water in other environments, such as a shaded or windy area. Have kids guess which trays will evaporate fastest. For a more complex experiment, try measuring evaporation rates on different days, comparing with measurements of the day's temperature and humidity. See whether there's a strong correlation between these different factors and the speed at which water evaporates.
Water Purification
Evaporation and condensation, important parts of the water cycle, are used by humans to purify water for different applications. Demonstrate the purification process by mixing water with sand or dirt in a large bowl. Carefully place a short glass or cup inside the bowl, such that the rim rises above the dirty water and the glass remains empty. Tightly cover the entire bowl with plastic wrap. Over time, water will evaporate from the bowl, condense on the plastic wrap, and precipitate into the cup. The water in the cup will be relatively clean, unlike the muddy water in the bowl. Try adding different substances, such as food coloring, to the bowl water and determine which can be removed through this purification method.
Storage and the Water Table
After precipitation, the land absorbs groundwater, changing the level of the water table. Below the water table line, the earth is entirely saturated with water. Kids can experiment to see how saturation works differently in different types of soil. Obtain several identical glass jars and fill them with different substances, such as sand, potting soil or semi-frozen dirt. Pour water into the jars and observe the amount of water that each substance can absorb as the water table rises in each glass. Extrapolate your findings to nature, and consider which environments flood more easily.
Hydrologic Cycle Models
By creating a model of the hydrologic cycle, kids can observe the phenomena of evaporation, condensation and precipitation in real time. In a glass jar with a metal lid, such as a jam jar, place a small amount of water. Close the lid and place ice cubes on top. Over the next ten minutes, water molecules will evaporate from the surface of the water and form water vapor inside the jar. The chilled lid will serve as a cold surface on which water vapor condenses. Finally, after enough water collects, droplets of "rain" will fall down into the bottom of the jar.