Introduction
Water is a necessity for life. It is the only form of matter that can be a solid, liquid, and a gas at Earthly temperatures. It is important for students to understand how the water cycle works. The water cycle is typically taught in 5th grade science. However, it is important that teachers keep in mind the big idea when it comes to teacher science, specifically water. According to Malonne I. Davies and C. Matt Seimears, "water is a common topic for study and investigation in chemistry, physics, and biology, as well as the Earth, atmospheric, and space sciences" (2008). Not only is water studied in many science fields, but it is also easily connected across different subject areas. An example of this is social studies. Bodies of water adn waterways have an important role in history especially during exploration, trade, and colonization. Despite that the water cycle is taught in science class, it is important that the teacher draws on activities and questions from other disciplines in order to increase student understand and critical-thinking skills. Along with this discussion, the article by Davies and Seimears includes two lesson sets with the water cycle that include multidisciplinary connections. (Davies & Seimears 2008).
The Water Cycle
The water cycle is made up of three parts: evaporation, condensation, and precipitation. Some sources, like the diagram above, also counts the collection of water as an additional step. Through these steps, water is transported from the land and oceans to the atmosphere and then back to the land and oceans. The water cycle is driven by the sun. It is the sun's heating of the water that causes evaporation. During evaporation the water changes from liquid water to water vapor. Once in the atmosphere, the water is cooled and becomes a cloud. The clouds lead to precipitation. During precipitation, the water falls back to earth in the form of rain, snow, or ice. After falling back to land, most of the water re-enters the water cycle. The water that does not evaporate flows into the streams, rivers, lakes, or underground aquifers.
This article also has a side note on the fact that the water cycle can change. This change occurs due to glacier retreating. This occurs when glaciers melt faster than their ice can be replaced. Glacier retreating limits the amount of fresh water on earth. Today, glacier retreating is occurring at it's fastest rate yet.
Saturn's Moon Has Water Cycle Too!
New evidence shows that Saturn's moon has lakes and a "water" cycle like the one that occurs on earth. However, the lakes on Titan (the name of Saturn's moon) are not filled with water. Instead, they probably consist of liquid methane. This is the cause of Titan's super-chilled climate. The lakes on Titan have been seen to be as big as 40 miles in diameter. The river-like channels that they found on Titan indicated to researchers that there was liquid methane falling as rain. However, not all the lakes had these channels sprouting from them. This suggested that there had to be some sort of aquifer that held the liquid methane just below the surface. This shows that if you would dig a giant hole on the surface of Titan, then it would fill with water. The article compares this suggestion to the Crater Lake in Oregon.
Researchers are amazed at the similarities that Titan has with Earth. If we were to go to Titan and stand at the shores of one of the lakes, it would look similar to what we are used to seeing. The water would be clear so you can see the pebbles at the bottom of the lake. Earth and Titan are the only two places in the solar system where water is present at the surface. As we discussed with the water cycle, water is necessary for life, so can there be life on Titan? Scientists say no because the temperatures are too cold to sustain any living organism. Temperatures on Titan are about -179 degrees Celsius (-290 degrees Fahrenheit. (Lovett 2007).
Teaching the Water Cycle
Above is a Bill Nye the Science Guy video on the water cycle. I suggest using this as a learning tool for students because Bill Nye does a good job of making science fun and interesting for students. He also includes a lot of experiments in his videos that could be implemented in the classroom. Personally, my favorite is the cloud in a jar experiment that is performed. I think that this could be implemented into a classroom and I think it is a good way to help students visualize an abstract concept. Because of my interest in this experiment, I went online to try and find specific steps and I was successful! So, here is a link to a pdf file of the experiment along with journal prompts and safety cautions.
I also came across another creative way to demonstrate the water cycle. I have seen this done before, but I especially like how the teacher wrote the cycle on the bag so that students could see what was happening to the water when it "disappeared" from the bag. I like this idea because it is an ongoing experiment that doesn't take a lot of time, it is mainly just observations.
References
Davies, M.I., & Seimears, C. (2008). Water: A topic for all sciences. Science Activities, 45(3), 27-36.Lovett, R.A. (2007). Saturn moon has lakes, "water" cycle like earth's, scientists say. National Geographic News. Retrieved (March 1, 2013) from http://news.nationalgeographic.com/news/2007/01/070105-saturn-titan.html
Rutledge, K., et al (2013). Water cycle. National Geographic Society. Retrieved (March 1, 2012) from http://education.nationalgeographic.com/education/encyclopedia/water-cycle/?ar_a=1
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