General Overview
Performance Expectation 2-ESS2-3: Obtain information to identify where water is found on Earth and that it can be solid or liquid.
Clarification Statement: Water is found in the ocean, rivers, lakes, and ponds. Water exists as solid ice and in liquid form.
Water is the most extraordinary substance on Earth. It is the only natural substance that exists in all three states, solid, liquid, and gas, under the temperature and pressure conditions found on Earth’s surface. It covers 71 percent of the planet’s surface in liquid form. It is stored in polar ice caps and mountain glaciers that together hold enough water to raise global sea levels by about 70 meters if they melted completely. It flows through rivers, seeps through soil into underground aquifers, evaporates from the ocean surface and rises into the atmosphere, and falls again as rain, snow, sleet, and hail. It is the medium in which all life on Earth evolved and in which most life still depends. There is no biological process on Earth that does not require water. And yet, despite its apparent abundance, the water that humans and most land-based life depend on, liquid fresh water, makes up less than one percent of all the water on Earth.
2-ESS2-3 asks second graders to use information from multiple sources to build a comprehensive picture of where water is found on Earth. The science and engineering practice is Obtaining, Evaluating, and Communicating Information: students gather data from texts, photographs, maps, and other sources to answer the question of where Earth’s water is. The disciplinary core idea is ESS2.C (The Roles of Water in Earth’s Surface Processes): water is found in the ocean, rivers, lakes, and ponds, and exists as both solid ice and liquid water. The crosscutting concept is Patterns: the distribution of water across Earth follows patterns related to climate, geography, and elevation that can be observed and described.
This standard connects directly to 2-ESS2-2 (maps as models of land and water distribution) and to K-ESS3-1 (living things including humans depend on natural resources, including water). At Grade 2, the standard focuses on recognition and description of where water is found. The explanation of how water moves between these locations, the water cycle, is introduced formally in Grade 5 (5-ESS2-1). However, teachers can plant the seeds of water cycle thinking by asking students to wonder: “If most of the water in this river came from rain, where did that rain come from? And where does river water go once it reaches the ocean?” These questions prepare students for the formal water cycle treatment without front-loading more content than the standard requires.
Scope and Sequence
In kindergarten, students built simple maps showing land and water features (K-ESS2-2) and learned that living things including humans need water to survive (K-ESS3-1). In Grade 1, students used observations of local weather to track precipitation patterns (1-ESS1 context). 2-ESS2-3 broadens and deepens these foundations by asking: where exactly is water found on Earth, in what forms, and in what relative amounts? This shifts from the local (our schoolyard, our town) to the global (Earth’s entire hydrosphere) and from qualitative observation (it rained today) to evidence-based classification (water on Earth exists in these locations, in these forms).
Also in Grade 2, 2-ESS2-2 developed the map-reading and map-making skills students need to interpret distributions of water bodies across Earth’s surface. Teaching 2-ESS2-3 after or alongside 2-ESS2-2 allows students to use their newly developed map literacy to locate and compare the major water bodies they are learning about. Similarly, 2-ESS1-1 established that Earth events include slow processes like erosion by water, and 2-ESS2-1 examined how water reshapes the land. 2-ESS2-3 completes the picture by addressing water as a feature of Earth’s surface in its own right, not just as an agent of change.
In Grade 5, students develop a model to describe the ways the geosphere, biosphere, hydrosphere, and atmosphere interact (5-ESS2-1). The water cycle, which describes how water moves through these spheres, is a centerpiece of this Grade 5 unit. Students who have a solid Grade 2 understanding of where water is found on Earth and in what forms are far better prepared to model the movement of water between these locations. In middle school, students analyze data on the distribution of water as evidence for Earth’s systems and connect patterns of water availability to patterns of biodiversity, human settlement, and agricultural potential. In high school, students model the global water cycle quantitatively and evaluate scenarios of climate change impacts on water availability. The Grade 2 foundation is the first systematic inventory of Earth’s water, and everything that follows builds on it.
What Students Must Understand
Water is found in many different locations on Earth, in both liquid and solid forms. Liquid water is found in oceans, which are the largest reservoirs of water on Earth and cover approximately 71 percent of its surface. Ocean water is salty, which means it cannot be drunk by humans or most land animals without treatment. Liquid water is also found in lakes, which are inland bodies of standing water enclosed by land on all sides. Most lakes contain fresh water, though some, like the Great Salt Lake in Utah and the Dead Sea between Israel and Jordan, are saltier than the ocean. Rivers are flowing bodies of fresh water that move downhill from mountains or highlands toward the sea or toward other rivers, lakes, or inland basins. Streams are smaller flowing water bodies that often feed into rivers. Ponds are small, shallow, enclosed bodies of standing water, similar to lakes but typically smaller and shallower.
Solid water, ice, is found primarily in two large formations. Glaciers are thick masses of ice that form in areas where more snow falls each winter than melts each summer, causing snow to compact and recrystallize over many years into ice. Most of the world’s glaciers are found in high mountain ranges and in polar regions. Ice caps and ice sheets are even larger formations: the Antarctic Ice Sheet covers virtually the entire continent of Antarctica and contains about 61 percent of all the fresh water on Earth. The Greenland Ice Sheet contains about 8 percent. Sea ice forms when ocean surface water freezes in polar regions; unlike glaciers, sea ice does not contribute to sea level rise when it melts because it is already displacing water.
A critical insight for students is that liquid fresh water, the water humans, animals, and plants need for survival, is surprisingly rare. Only about 3 percent of all water on Earth is fresh water, and about 69 percent of that fresh water is locked in glaciers and ice caps. Only about 30 percent of Earth’s fresh water is found as groundwater, and less than 1 percent is found in surface water in lakes, rivers, and ponds. This means that the rivers, lakes, and ponds that support almost all terrestrial life represent a tiny fraction of Earth’s total water inventory. This scarcity and uneven distribution, combined with the fact that human water use is growing rapidly as population increases, makes the protection of fresh water one of the most important environmental challenges of the 21st century.
Water also exists as water vapor in the atmosphere, though students are not required to inventory atmospheric water at this grade level. Teachers can mention it as a preview: “We have found water in the ocean, in rivers and lakes, and in glaciers and ice. Is there water in the air around us right now? Where does the water in clouds come from?” These questions point toward the water cycle content of Grade 5 without requiring mastery here.
Key vocabulary includes: ocean, sea, lake, river, stream, pond, glacier, ice cap, ice sheet, fresh water, salt water, liquid, solid, hydrosphere, precipitation, evaporation, groundwater, and distribution.
Lesson Ideas and Activities
The Water on Earth survey is the core information-gathering activity for this standard. Over two to three days, students rotate through five or six information stations, each containing a different source about a specific location where water is found on Earth. Station topics might include the Atlantic Ocean (text and photograph), the Amazon River (text, map, and photograph), the Antarctic Ice Sheet (text, photograph, and diagram), the Great Lakes (map and informational text), a high-altitude glacier in the Himalayas (photograph and text), and a local river or lake familiar to students. At each station, students use a recording sheet to answer: what type of water body is this, where is it located, is the water fresh or salty, is it liquid or solid, and what lives there or depends on it? After completing all stations, students gather as a class to build a master data chart and discuss: “Which water bodies are fresh and which are salty? Which are liquid and which are solid? Where is most of Earth’s water found?”
A water distribution demonstration makes the scarcity of fresh surface water viscerally real. Fill a large container with 100 cups of water representing all water on Earth. Pour 97 cups into a bowl labeled “salt water oceans.” Of the 3 cups remaining representing all fresh water, pour 2 cups and most of the third cup into a bowl labeled “glaciers and ice caps.” From what remains in the third cup, pour most of it into a small cup labeled “groundwater.” Then ask students to look at the tiny amount of water left: “This is all the surface fresh water on Earth: all the rivers, lakes, ponds, and streams that most life on land depends on.” The physical scale of this demonstration is far more memorable than any pie chart and directly motivates the importance of fresh water protection.
Map-based investigation of global water distribution connects 2-ESS2-3 directly to the modeling skills developed in 2-ESS2-2. Provide students with a world map and a set of stickers or markers in different colors representing different types of water bodies. Students use the information they gathered in the station activity to add water body markers to the world map: blue for ocean, green for major rivers, light blue for major lakes, white for glaciers and ice sheets. When the map is complete, ask: “Where is most of the water on Earth? Where are most of the glaciers? Where are most of the large rivers? Can you see any patterns in where different types of water are found?” This integrates geography, patterns thinking, and the content knowledge of 2-ESS2-3 into a single coherent artifact.
Comparing fresh water and salt water through direct investigation builds conceptual understanding of the fresh/salt distinction through experience rather than just description. Prepare four unlabeled containers of water: plain tap water, salt water (made with enough salt to approximate ocean salinity at about 35 parts per thousand), slightly salty water (about half ocean salinity), and distilled water. Students use their senses (taste with appropriate hygiene protocols or smell, or observe what happens when the water evaporates from a dark surface) to rank the containers from least to most salty. Then reveal: “Ocean water is about as salty as the saltiest sample. Why can humans not drink ocean water? What would happen to your body if all the water you drank was this salty?” This grounds the fresh/salt distinction in physical reality rather than leaving it as an abstract category.
A glacier investigation using ice models connects the solid form of water to the concepts of change over time from 2-ESS1-1. Create simple glaciers in class by packing crushed ice into trays with sand and small rocks mixed in. Place the trays in a warm location and observe what happens over a class period: the ice melts, carrying sand and pebbles with it and depositing them as the melt water flows. Ask students: “Where did the rocks and sand come from? Where did they end up? What does this tell us about what real glaciers do to the landscape over long periods of time?” This activity connects the solid/liquid distinction of 2-ESS2-3 to the erosion and deposition concepts of 2-ESS2-1 and to the slow Earth change timescale of 2-ESS1-1.
The water journey story writing activity integrates science with ELA narrative writing standards. Students write a short story from the perspective of a water molecule, starting in a specific location (the ocean, a glacier, a river, a lake, or a cloud) and traveling to at least two other water locations. The story must be scientifically accurate about what type of water body each location is and whether the water is liquid or solid. This creative assignment requires students to apply and organize their factual knowledge in a narrative format, which both consolidates learning and makes it memorable. Sharing stories in a class read-aloud reveals the diversity of water journeys possible on Earth and naturally previews the water cycle.
Common Student Misconceptions
The most deeply rooted misconception is that most of Earth’s water is fresh and drinkable. This misconception is understandable: the water that students interact with directly at home, at school, and in nature is almost always fresh water, so it feels ubiquitous. The water distribution demonstration described above is the most effective tool for challenging this belief, because it makes the rarity of surface fresh water physically visible in a way that no verbal explanation can match. Once students genuinely understand how scarce surface fresh water is, the importance of water conservation and water quality protection becomes self-evident rather than abstract.
A second misconception is that glaciers and ice caps are static, permanent features of Earth’s landscape. In fact, most glaciers on Earth are currently retreating, some very rapidly, as a result of rising global temperatures. Showing before-and-after photographs of the same glacier taken decades apart is one of the most compelling and empirically direct pieces of evidence for large-scale environmental change that is accessible to second graders. It also connects to 2-ESS1-1 (Earth changes) and 2-ESS2-1 (solutions to environmental change) in meaningful ways. The appropriate message at Grade 2 is not to alarm students but to connect the science: “Scientists have photographs showing that many glaciers have gotten much smaller over the past 100 years. What does this tell us about what is happening to the solid water stored in glaciers? If glaciers melt, where does that water go?”
A third misconception is that rivers flow from the ocean to the mountains. This misconception often develops when students encounter the water cycle concept informally before they understand the distinction between where water flows as liquid on the surface (always downhill, from mountains to sea) and where water moves as vapor through evaporation and precipitation. Students who have this misconception will make errors in map interpretation, believing that rivers flow uphill toward their source, and will have difficulty understanding drainage basins and watershed concepts. The stream table investigation from 2-ESS2-1 and the class discussion about rivers in 2-ESS2-2 both address this, but teachers should check explicitly: “Which direction does river water flow? Does it flow toward the ocean or away from the ocean?”
A fourth misconception is that groundwater is a separate, underground ocean. Students who have heard about groundwater or wells may imagine a large cavern of liquid water beneath the soil surface, like a subterranean lake. In reality, most groundwater exists as water filling the tiny spaces between sand grains, gravel, and rock in underground formations called aquifers, similar to how water fills the spaces in a wet sponge. A very small amount of groundwater is found in true underground streams and caves, but this is the exception rather than the rule. Showing a cross-section diagram of soil layers with water filling the pore spaces effectively communicates this more accurate model.
A fifth misconception is that ocean water is always deep. Students may be surprised to learn that coastal ocean areas can be quite shallow and that large shallow seas have existed in the interior of continents at various points in Earth’s history. The average depth of the ocean is about 3,700 meters, but continental shelves, which extend from coastlines for varying distances, are often only 50 to 200 meters deep. These shallow coastal areas are among the most biologically productive places in the ocean and support most of the world’s fisheries. This is also relevant to the erosion content of 2-ESS2-1: coastlines erode differently depending on how deep the adjacent ocean is.
A sixth misconception is that fresh water and salt water cannot mix. Because students learn to categorize water as either fresh or salt, they sometimes develop an implicit model in which these two types of water stay completely separate. In reality, rivers continuously discharge fresh water into the ocean. In estuary zones where rivers meet the sea, the water is brackish, meaning it has an intermediate salinity that varies with the tides, rainfall, and distance from the river mouth. Estuaries are among the most productive ecosystems on Earth, precisely because the mixing of fresh and salt water creates a unique and nutrient-rich environment. The fresh/salt distinction is a useful simplification but should not be taught as an absolute boundary.
Assessment Questions
Name four different places where water can be found on Earth. For each place, tell whether the water is fresh or salty and whether it is liquid or solid.
What is the difference between a glacier and a lake? What do they have in common? Where on Earth would you expect to find each one?
Imagine you are looking at a world map. Where would you expect to find most of Earth’s liquid salt water? Where would you expect to find most of Earth’s solid fresh water? Where would you find the rivers and lakes that most land animals depend on?
After doing the water distribution activity in class, a student says: “I never realized how little fresh surface water there is. It makes me want to be more careful about how much water I waste.” What do you think this student understood about Earth’s water that they did not know before?
Can you drink water directly from the ocean? Why or why not? What would need to happen to ocean water before humans could drink it? Does this tell you anything about why fresh water is important?
A scientist discovers photographs of a mountain glacier taken in 1920 and in 2020. The glacier is much smaller in the 2020 photograph. What does this evidence tell you? What questions would you want to investigate next?
A student says, “Glaciers are too far away to matter. They are just frozen water in places where nobody lives.” Do you agree or disagree? What information about where fresh water comes from would help you respond?
Look at this world map showing the locations of Earth’s major rivers and lakes. What patterns do you notice about where fresh water bodies are found? Are they spread evenly around the world or concentrated in certain areas? What might cause some areas to have more fresh water than others?
Write a short story from the point of view of a water drop. Your story must include at least two different places where water is found on Earth. Make sure your story accurately describes whether the water is liquid or solid and fresh or salty in each place it visits.