This is the new updated edition of the first book in the bestselling Uncovering Student Ideas in Science series. Like the first edition of volume 1, this book helps pinpoint what your students know (or think they know) so you can monitor their learning and adjust your teaching accordingly. Loaded with classroom-friendly features you can use immediately, the book includes 25 “probes”—brief, easily administered formative assessments designed to understand your students’ thinking about 60 core science concepts.

Access this probe as a Google form: English

Download this probe as an editable PDF: English

The purpose of this assessment probe is to elicit students’ ideas about precipitation. The probe is designed to determine whether students understand what causes the water in clouds to fall as rain.

Friendly Talk

clouds, gravity, precipitation, rain, water cycle

The best answer is Marcus’s: I think rain falls when water drops in the clouds get too heavy. Rain is the liquid form of precipitation. Precipitation is a complex process. A simple explanation begins with water vapor in the warm air rising in the sky, cooling to the dew point (where condensation occurs), and forming tiny drops of suspended liquid water. When there are enough of these tiny drops of suspended liquid water, they accumulate to form clouds. As the drops accumulate, some of the drops will combine and form larger drops, and some drops will acquire more water vapor from the air. Clouds often appear gray when they contain larger water drops. Eventually the large drops are too heavy to remain suspended in the sky and succumb to the pull of gravity from the Earth. This pull of gravity causes the water to fall from the clouds toward Earth, resulting in rain.

Elementary Students

In the early elementary school grades, the emphasis should be on observing and describing weather, including rain events. Observing rain and recording data, such as observations of clouds when it rains, amount of rain, days when it rains, and temperature, helps students form a foundation for understanding weather phenomena. Pondering questions, such as why rain does not always fall from the clouds, helps students begin to understand that there are certain conditions necessary for rain to occur. At the upper elementary level, students are beginning to develop a basic conception of gravity as a pull toward the Earth. Students can begin to link the concept of rain falling toward the Earth with gravity, but an understanding of what is happening within the cloud that causes the rain to fall should wait until middle school.

Middle School Students

Middle school students expand on their elementary experiences in observing and describing rain clouds to more conceptual ideas about the water cycle, including the composition and formation of rain clouds and the mechanism of precipitation. Students’ growing understanding of the relationship between the mass of an object, the upward force of rising air, and the downward force of gravity will help them account for why large drops of water fall toward the Earth while tiny drops stay suspended in clouds.

High School Students

At the high school level, students use their knowledge of physics- and chemistry-related concepts to explain weather phenomena in the Earth system, such as rain. Their understanding of the water cycle is set into the larger context of matter cycling through Earth as a system. Recognizing the role of gravity is important to their growing understanding of Earth as a system because, without gravity, there would be no water cycle. Their deepening knowledge of heat, temperature, change in state, evaporation, condensation, and the force of gravity is helpful in understanding why the water cycle occurs and knowing the processes that make up the water cycle.

All students have seen rain fall from clouds in the sky, although in some geographic areas, rain is a more common occurrence. If possible, take students outside to view rain as it falls. This probe can be used with other probes in this book, such as “What Are Clouds Made Of?” (p. 155) and “Where Did the Water Come From?” (p. 163), or combined with “Wet Jeans” from Volume 1 of this series (Keeley, Eberle, and Farrin 2005) to create a cluster of water cycle–related probes.

• Some younger students believe that clouds get scrambled and melt and rain occurs when clouds are shaken (Philips 1991).
• A study by Bar (1986) revealed that when students ages 5–7 were asked what causes rain, there was little evidence of a relationship between clouds and rain. Those who did see a link between rain and clouds often described clouds as bags of water kept high in the sky, and when they collide, they rip open and the water falls out. The same study found that at ages 6–9, students think the clouds open up to make rain. Building on that idea, students in grades 7–10 further described rain as the drops that fall through little holes in the clouds. At ages 9–10, some students think rain falls when clouds become cold or heavy (Driver et al. 1994).
• Field tests of this probe with fourth through eighth graders reveal that many students think that clouds are made up of water vapor and that, when the water vapor condenses, it falls as rain. These students did not recognize the clouds as being made up of tiny drops of water. They explain water as evaporating and going up to the clouds, then condensing and falling as rain, but fail to recognize that clouds can exist as tiny droplets of water long before it rains.

American Association for the Advancement of Science (AAAS). 1993. Benchmarks for science literacy. New York: Oxford University Press.

American Association for the Advancement of Science (AAAS). 2007. Atlas of science literacy. Vol. 2, “weather and climate,” 20–21. Washington, DC: AAAS.

Crane. P. 2004. On observing the weather. Science and Children 41 (8): 32–36.

Driver, R., A. Squires, P. Rushworth, and V. Wood- Robinson. 1994. Making sense of secondary science: Research into children’s ideas. London and New York: RoutledgeFalmer.

Keeley, P. 2005. Science curriculum topic study: Bridging the gap between standards and practice. Thousand Oaks, CA: Corwin Press.

National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academy Press.

Robertson, W. 2005. Air, water, and weather: Stop Faking It! Finally Understanding Science So You Can Teach It. Arlington, VA: NSTA Press.

Vowell, J., and M. Phillips. A drop through time. Science and Children 44 (9): 30–34.

Williams, J. 1997. The weather book: An easy-tounderstand guide to the USA’s weather. 2nd ed. Arlington, VA: NSTA Press.

• Provide younger students with opportunities to make relatively long-term sky observations of clouds to begin to understand that rain does not occur just because clouds are present. Visually observing the changes that happen to clouds before it rains sets the stage for later explanations of what happens in clouds that results in precipitation.
• Do not assume that because students use words like evaporation, condensation, and precipitation they actually know what is happening. Develop the concept before giving students the technical term for the processes that make up the water cycle.
• Ask students to draw a sequence of pictures to show and explain what happens to the water drops that make up clouds before and during a rain.
• Be aware of poor diagrams of the water cycle that often show water evaporating and rising to form a white cloud and then moving to a dark cloud that appears to open up and spill out streams of water. Poor representations like this are pervasive on the internet and should be used with caution.
• When teaching about Earth’s gravity as a force that affects all objects on or near the Earth, explicitly connect the fall of rain to gravity and the concept of mass. Challenge students to think about why the effect of gravity on a large water drop in a cloud is different from the effect of gravity on a tiny water drop or rising water molecules.
• Probe further to find out what students think clouds are made of by using the probe “What Are Clouds Made Of?” (p. 155). Some students think that when water evaporates, it forms a cloud made up of evaporated water and that rain is the result of the water condensing and falling. Understanding what clouds are made of is connected to students’ ideas about the fall of rain.