An easy-to-follow planning strategy Do-Talk-Do provides the structure for an integrated unit on the water cycle for fifth-grade students. By Julie Vowell and Marianne Phillips 30 Science and Children
id you know that the water you use today is the same water that was used millions of years ago? How is this possible? Water is continuously replenished through a naturally occurring process known as the water cycle. To help students learn about this important concept, we created an eight-day unit for fifth-grade students to explore the water cycle and its components, including evaporation, condensation, and precipitation. Our unit uses the Do-Talk-Do instructional strategy (Kemper and Ramsey 1997), an easy-to-follow planning strategy for teachers that involves students in authentic hands-on experiences, social interaction, and concept development based on prior knowledge. Here s how the strategy played out in our water cycle unit. The First Do Do-Talk-Do begins with a concrete experience that serves as a baseline for learning. In the water cycle lessons, the first Do is comprised of three concrete experiences that separately introduce the main components cycle precipitation, evaporation, and condensation. A final discussion, Talk, links the three. Any new terminology or formal discussion about the water cycle is reserved for Talk. Evaporation Evaporation occurs when there is sufficient heat for water molecules to separate from the surface of liquid water and enter a gaseous state. The rate of evaporation is affected by temperature, wind, surface area, Keywords: Water cycle at www.scilinks.org Enter code: SC070704 Summer 2007 31
and level of humidity. For example, when it is hot outside, water molecules move more quickly, enabling them to evaporate more quickly into the air. To illustrate evaporation, the teacher wipes a damp sponge across a chalkboard. The students watch and make observations about what happens. Some may think that the water soaks into the blackboard. The teacher explains that the water changed from a liquid to a vapor. The class should come to understand that the water evaporated but is still in the air. The water evaporates faster with wind (blowing on the blackboard) or increasing surface area (spreading the water out). After a short discussion of the cause for the water s disappearance (effect of the temperature and increase in surface area), the class is divided into groups for the next activity. Each group of students gets a plate and three different colored crayons. They should make a shallow puddle of water on their plate. Then, they should use a purple crayon to make a circle around their puddle of water. Instruct each group to choose different places in the room to place their plate (e.g., in the Sun, in the shade, near a fan). Let the plates sit for about an hour. During that time, have students make several predictions about what will happen to the water: Will the amount of water on the plate remain the same? If not, what change will occur? Which plate will have the least amount of water after one hour? While the students are waiting to check their puddles, the teacher can read a book about water. Water Dance by Thomas Locker (1997) provides an excellent visual and instructional tool for helping students develop their conceptual understanding cycle. After one hour has passed, instruct students to check their puddles. Each group should make an orange circle around their puddles if the puddles have changed any. (The puddles should shrink.) Then different groups can walk around the room to observe and compare all of the plates while the teacher records on the board student observations of which plate had the most water, the least, etc. Have the groups leave their plates where they are overnight. The next day, have the students draw a circle with a black crayon around their puddle if there are any changes. The groups should compare the puddles again. Then, remind the students of their predictions. s should come to the conclusion that evaporation occurred, that it occurred at a higher rate for those plates with less water originally, and that plates in warmer locations (in a sunny window, etc.) had higher rates of evaporation. Condensation Condensation is the process of water vapor changing back to liquid water. To help students experience condensation, have a cup full of ice water on the U.S. Geological Survey http://ga.water.usgs.gov/edu/watercycle.html center of each table. Begin the session with the questions: Why are there drops on the outside of the cup? Where did they come from? What is happening? The students might believe that the water on the glass sweats through small pores. To gain a better understanding of what happened, the teacher will engage the class in the activity Cloud in a Bottle. For this activity, each group will need a pintsized plastic jar, a plastic bag of ice that snugly covers over the jar opening, and a sheet of black paper. Have the students tape the paper on the back half of the jar so they can t see through it. Let students fill one-third of the jar with warm water. The teacher (not students) should light a match and hold it over the jar opening. After a few seconds, drop the match in the jar, and cover the top with the bag of ice. The match introduces smoke particles into the bottle, enhancing the condensation. s should observe the inside of the jar and record and discuss their observations with their group. s might describe the bottle as looking smoky, foggy, or cloudy inside. The system in the jar can be compared to our atmosphere, in which there is water vapor. In the jar, water vapor condenses on particles, such as the smoke from a match, whereas in the atmosphere cloud droplets are formed around particles of dust, salt, or soil. These particles serve as condensation nuclei. In clouds, droplets merge with many other cloud droplets, becoming heavy enough to return to Earth as precipita- 32 Science and Children
Figure 1. Story rubric. Organization creatively written. All parts of the water cycle are stated in a logical sequence. Criteria 5 4 3 2 1 All parts of the water cycle are stated in a logical sequence. One part of the water cycle is missing. Reader has difficulty following the story because student jumps around. poorly written. Some steps of the water cycle are missing. Points Content Knowledge exhibits knowledge of all parts cycle. Story is creatively written and correct. exhibits general understanding cycle. However, story lacks details. confuses one of the parts cycle. confuses two parts cycle. confuses two parts of the water cycle. Story lacks details. Grammar and Spelling All story and spelling is correct. one or spelling error. two and/or spelling three and/or spelling four or more and/or spelling Neatness neatly written. one part that is sloppy. two parts that are sloppy. three or four parts that are sloppy. illegible. Total tion, which allows for evaporation to occur with the entire process continuing. Precipitation Precipitation occurs when water vapor condenses and falls to the Earth. Following the condensation demonstration, the students visit weather websites (such as weather.com) to research precipitation levels in cities around the world and at home and compare them (students can also find this information in newspapers). Noting the different levels of precipitation around the world will encourage the students to reflect on the effects of precipitation and begin to understand the global nature cycle. s can plot precipitation on maps. They may associate types of precipitation or amounts of precipitation with geographic locations. Talk During Talk, the teacher helps students verbalize their ideas and make inferences based upon their observations from the initial Do experiences. At this time, the teacher should try to clarify any misconceptions. In the water cycle unit, talk begins with a class discussion and introduction of important terms. The teacher explains that the experiences they observed Summer 2007 33
describe the continuous movement of water that makes up the water cycle. Evaporation (as observed through the chalkboard and paper plate demonstrations) occurs when heat causes water to change to a gas. Once the water has turned into a gas, it cools and changes into a liquid in the atmosphere. This process of condensation (as observed through the jar, match, and ice demonstration) forms clouds. Eventually, those water droplets fall to the ground as precipitation (as students confirmed through their recording of various precipitation levels around the globe). The water will evaporate, soak into the ground, or run along the surface into another body of water such as a lake, river, or stream. After the terms are introduced, students break into small groups to process their understanding cycle by answering such questions as, Where does the water go? How do the parts of the water cycle fit together? What would happen if one part was left out? Finally, the class reassembles as a large group and the teacher places a diagram cycle on the overhead. The teacher leads an interactive discussion cycle. Typically, students share their understanding as: Evaporation occurs when heat from the Sun causes water to change to a gas. Once the water has turned into a gas, it cools and changes into a liquid form in the atmosphere (known as the process of condensation). Condensation results in cloud formation. Eventually, the clouds become too heavy or saturated with water, and the water returns to the ground as rain, sleet, snow, or hail (precipitation). The precipitation will either soak into the ground or run off the land into a body of water such as an ocean, river, lake, or stream. Through this discussion, students reveal their understanding that the water cycle is continuous. The Final Do After the synthesizing talk, students move on to the final Do. In this phase of instruction, students transfer their newly formed concepts and skills to new situations. In the water cycle unit, students with previous inquiry experience (i.e., asking testable questions, controlling variables, designing predictions, collecting data, analyzing data, and making conclusions) could conduct an open inquiry in which they ask a new question of their own (e.g., Is there a difference between the salt water cycle and fresh water cycle?) and then design an investigation to explore it (e.g., such as creating a salt water system setup and fresh water system setup and comparing the two). In an open inquiry, the teacher facilitates students investigations, offering guiding questions and addressesing safety issues and other assistance, but students devise the methods needed to collect data and test their predictions themselves. These additional explorations and the ownership of the open-inquiry process itself can lead students to a broader understanding of the topic. Assessment By the end of their inquiry experiences in the final Do, students will have a developing understanding cycle. As a summative evaluation, ask students to write a creative story that describes each of the processes cycle: precipitation, evaporation, and condensation. The stories can then be shared with the class and graded using the rubric in Figure 1 (page 33). All aspects cycle should be creatively presented and discussed within the story: One day a drop of water (in solid form) was sitting on top of a hill in the middle of the country. He was close to all of his friends because he was with them in a pile of snow. A few hours passed and the Sun began to shine. The Sun was bright that afternoon, and the tiny drop of water started to feel warm. All of a sudden. The students should take the water droplet through each phase cycle (e.g., precipitation, evaporation, and condensation). When presented using the Do-Talk-Do method these simple activities not only introduce an essential science concept, they also serve as a starting point for verbal discussion and complex thinking, an important aspect of any science class. n Julie Vowell (julievowell@sbcglobal.net) is a doctoral student at the University of Houston in the Department of Curriculum and Instruction specializing in science education. Marianne Phillips (mmcp_uh@ yahoo.com) has recently graduated from the University of Houston doctoral program in Curriculum and Instruction specializing in science education. Resources Kemper, J., and Ramsey, J. 1997. Facilitate science learning in elementary and middle school. Champaign, IL: Stipes. Locker, T. 1997. Water dance. New York: Harcourt. National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academy Press. Internet Weather.com www.weather.com Zoom School: The Water Cycle www.enchantedlearning.com/subjects/astronomy/planets earth/watercycle.shtml 34 Science and Children