Polar Science Assessment Probes 1. How Much Water?

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1 Polar Science Assessment Probes 1 Luisa and Stephanie are reading about Earth s history. They learn that Earth is very old. As they read, they stop and share what they have learned with each other, and ask questions to make sure they understand. If they can t answer the questions, they try to find answers in the books that they are reading. Luisa starts reading a section called Earth s Water. She asks Stephanie a question: How does the amount of water on Earth now compare with the amount 1,000 years ago? Luisa and Stephanie don t know the answer, so they decide to keep reading to find out. Help the girls answer their question! How does the amount of water on Earth now compare with that 1,000 years ago? There is more water now than there was 1,000 years ago. There is less water now than there was 1,000 years ago. There is the same amount of water now as there was 1,000 years ago. Please explain the thinking you used to make your choice.

2 Polar Science Assessment Probes 2 Teacher Notes Purpose The purpose of this assessment probe is to elicit students ideas about the conservation of water. The probe is designed to examine students ideas about the water cycle and whether the amount of earth s water has changed over time. Related Concepts conservation of matter, water cycle, phase changes, clouds, rain Explanation The best response is that there is the same amount of water as there was 1,000 years ago. Water moves throughout the natural and designed world in an ongoing process called the water cycle. The water cycle includes evaporation of water from bodies of water, living things, the soil, and snow and ice cover, condensation of water vapor, and precipitation (rain, sleet, hail, and snow). The water cycle includes both surface and groundwater, fresh water and salt water. While water may seem to be removed from the cycle in ice caps, glaciers, and human uses, it remains in the cycle throughout the longer geologic time scale. Curricular and Instructional Considerations Elementary students are concrete thinkers who primarily rely on firsthand observation. Abstract concepts such as properties of a gas, evaporation, and condensation are difficult for students who cannot directly observe or visualize them. As students develop, they are better able to understand conservation of matter and these processes. Students in the elementary grades also have difficulty generalizing and thinking about global systems. They tend to consider concepts like the water cycle on a local level and tend to confuse local changes with global ones. Students of any age may think that there is more water now because they have observed rain and snow, but have not directly observed the process of evaporation. Alternatively, students may have heard about water shortages and water conservation and confuse a lack of fresh water in parts of the country and/or world with a decline in the total amount of water on the earth. Students may also select different answers if the question is rephrased using different amounts of time (1, 10, or 100 years? one day ago? one week ago?). In this case, students may confuse shortterm, local weather events like heavy rainfall or a drought with the global water cycle.

3 Polar Science Assessment Probes 3 In the probe, Luisa and Stephanie are modeling the use of content area reading in science as well as the comprehension strategies of questioning and summarizing an excellent point to discuss with students. Administering the Probe This probe is best used to determine whether or not students understand the conservation of water. It can be used as an anticipatory set before instruction about the water cycle, or after instruction to assess student understanding of the cycle on a global level. Related Ideas in National Science Education Standards (NRC, 1996) K-4 Properties of Objects and Materials Materials can exist in different states solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling. 5-8 Structure of the Earth System Water, which covers the majority of the earth s surface, circulates through the crust, oceans, and atmosphere in what is known as the water cycle. Water evaporates from the earth s surface, rises and cools as it moves to higher elevations, condenses as rain or snow, and falls to the surface where it collects in lakes, oceans, soil, and in rocks underground. Related Ideas in Benchmarks for Science Literacy (AAAS, 1993) K-2 The Earth Water can be a liquid or a solid and can go back and forth from one form to the other. If water is turned into ice and then the ice is allowed to melt, the amount of water is the same as it was before freezing. Water left in an open container disappears, but water in a closed container does not disappear. 3-5 The Earth When liquid water disappears, it turns into a gas (vapor) in the air and can reappear as a liquid when cooled, or as a solid if cooled below the freezing point of water. Clouds and fog are made of tiny droplets of water. 6-8 The Earth The cycling of water in and out of the atmosphere plays an important role in determining climatic patterns. Water evaporates from the surface of the earth, rises and cools, condenses into rain or snow, and falls again to the surface. The water falling on land collects in rivers and lakes, soil, and porous layers of rock, and much of it flows back into the ocean.

4 Polar Science Assessment Probes 4 Fresh water, limited in supply, is essential for life and also for most industrial processes. Rivers, lakes, and groundwater can be depleted or polluted, becoming unavailable or unsuitable for life. Related Research When assessing misconceptions regarding the water cycle, it is necessary to consider interrelated concepts such as the conservation of matter, phase changes, clouds, and rain. Evaporation Students tend to progress through a series of stages of conceptual understanding about evaporation, initially believing that when water evaporates, it no longer exists, that it remains a liquid but changes location, or that it is transformed in another perceptible form such as fog or steam (Bar, 1989; Russell, Harlen, & Watt, 1989; Russell & Watt, 1990). Students in fifth grade may identify the air as the final location for evaporating water (Russell & Watt, 1990) if they accept air as a permanent substance (Bar, 1989). Conservation of Matter Before understanding conservation of matter and weight, students need to understand what matter is, that weight is an intrinsic property of matter, and the difference between weight and density (Lee et al., 1993; Stavy, 1990). By fifth grade, students may be able to understand matter conservation in phase changes (Stavy, 1990). Suggestions for Instruction and Assessment Related NSTA Science Store Publications and Journal Articles Adler, B Teaching through trade books: Water wherever. Science and Children 41 (5): Damonte, K The home zone: Water for life. Science and Children 40 (6): Keeley, P., F. Eberle, and L. Farrin Uncovering student ideas in science, vol. 1: 25 formative assessment probes. NSTA Press. Keeley, P., F. Eberle, and J. Tugel. 2007: Uncovering student ideas in science, vol. 2: 25 more formative assessment probes. NTSA Press. Keeley, P., F. Eberle, and C. Dorsey Uncovering student ideas in science, vol. 3: Another 25 formative assessment probes. NSTA Press. McDuffie, T Precipitation matters. Science and Children 44 (9):

5 Polar Science Assessment Probes 5 Toft, J. and K. Scoggin The ripple effect. Science and Children 45 (3): Vowell, J. and M. Phillips A drop through time. Science and Children 44 (9): Related Publications American Association for the Advancement of Science (AAAS) and National Science Teachers Association (NSTA) Atlas of science literacy. Washington, DC: AAAS and NSTA. American Association for the Advancement of Science (AAAS) Benchmarks for science literacy. New York: Oxford University Press. National Research Council (NRC) National science education standards. Washington, DC: National Academies Press. References American Association for the Advancement of Science (AAAS) Benchmarks for science literacy. New York: Oxford University Press. Bar, V Children s views about the water cycle. Science Education, 73, Henriques, L. Children's misconceptions about weather: A review of the literature. National Association of Research in Science Teaching annual meeting, New Orleans, 29 April Keeley, P., F. Eberle, and L. Farrin Uncovering student ideas in science, vol. 1: 25 formative assessment probes. NSTA Press. Keeley, P., F. Eberle, and J. Tugel Uncovering student ideas in science, vol. 2: 25 more formative assessment probes. NTSA Press. Keeley, P., F. Eberle, and C. Dorsey Uncovering student ideas in science, vol. 3: Another 25 formative assessment probes. NSTA Press. Lee, O., D.C. Eichinger, C.W. Anderson, G.D. Berkheimer, and T.S. Blakeslee Changing middle school students conception of matter and molecules. Journal of Research in Science Teaching, 30, National Research Council (NRC) National science education standards. Washington, DC: National Academies Press. Russell, T., W. Harlen, and D. Watt Children s ideas about evaporation. International Journal of Science Education, 11,

6 Polar Science Assessment Probes 6 Russell, T. and D. Watt Evaporation and condensation. SPACE Project Research Report. Liverpool, UK: Liverpool University Press. Stavy, R Children s conceptions of changes in the state of matter: From liquid (or solid) to gas. Journal of Research in Science Teaching, 27,