8.3.2.3 Water Cycle
Describe the location, composition and use of major water reservoirs on the Earth, and the transfer of water among them.
Describe how the water cycle distributes materials and purifies water.
For example: Dissolved gases in rain can change the chemical composition of substances on Earth.
Another example: Waterborne disease.
Overview
MN Standard in Lay Terms
Water exists on earth in the solid, liquid, and gas states. The water on earth is constantly moving through processes of evaporation, condensation, and precipitation through the oceans, the crust, and the atmosphere. The basic water cycle diagram sometimes fails to make clear that this process provides clean fresh water from evaporated salt water, and through the filtration that occurs as water enters the ground water system. As water moves through this cycle, it is also redistributed from the large reservoirs of the ocean to the continents by global patterns of atmospheric movement.
Big Idea
From the Earth Science Literacy Initiative
Big Idea 3. Earth is a complex system of interacting rock, water, air, and life.
3.1 The four major systems of Earth are the geosphere, hydrosphere, atmosphere, and biosphere. The geosphere includes a metallic core, solid and molten rock, soil, and sediments. atmosphere is the envelope of gas surrounding Earth. The hydrosphere includes the ice, water vapor, and liquid water in the atmosphere, the ocean, lakes, streams, soils, and groundwater. The biosphere includes Earth's life, which can be found in many parts of the geosphere, hydrosphere, and atmosphere. Humans are part of the biosphere, and human activities have important impacts on all four spheres.
3.2 All Earth processes are the result of energy flowing and mass cycling within and between Earth's systems. This energy is derived from the sun and Earth's interior. The flowing energy and cycling matter cause chemical and physical changes in Earth's materials and living organisms. For example, large amounts of carbon continually cycle among systems of rock, water, air, organisms, and fossil fuels such as coal and oil.
3.3 Earth exchanges mass and energy with the rest of the Solar System. Earth gains and loses energy through incoming solar radiation, heat loss to space, and gravitational forces from the sun, moon, and planets. Earth gains mass from the impacts of meteoroids and comets and loses mass by the escape of gases into space.
3.4 Earth's systems interact over a wide range of temporal and spatial scales. These scales range from microscopic to global in size and operate over fractions of a second to billions of years. These interactions among Earth's systems have shaped Earth's history and will determine Earth's future.
3.6 Earth's systems are dynamic; they continually react to changing influences. Components of Earth's systems may appear stable, change slowly over long periods of time, or change abruptly with significant consequences for living organisms.
3.7 Changes in part of one system can cause new changes to that system or to other systems, often in surprising and complex ways. These new changes may take the form of "feedbacks" that can increase or decrease the original changes and can be unpredictable and/or irreversible. A deep knowledge of how most feedbacks work within and between Earth's systems is still lacking.
Big Idea 5. Earth is the water planet.
5.1 Water is found everywhere on Earth, from the heights of the atmosphere to the depths of the mantle. Early in Earth's history, surface water accumulated through both outgassing from its interior and the capture of some extraterrestrial ice. Water vapor in the atmosphere condensed and rained out as the planet cooled.
5.3 Water's unique combination of physical and chemical properties are essential to the dynamics of all of Earth's systems. These properties include the manner in which water absorbs and releases heat, reflects sunlight, expands upon freezing, and dissolves other materials.
5.5 Earth's water cycles among the reservoirs of the atmosphere, streams, lakes, ocean, glaciers, groundwater, and deep interior of the planet. The total amount of water at Earth's surface has remained fairly constant over geologic time, although its distribution among reservoirs has varied.
5.8 Fresh water is less than 3% of the water at Earth's surface. Most of this fresh water is stored as glaciers in Antarctica and Greenland. Less than 1% of Earth's near-surface water is drinkable liquid fresh water, and about 99% of this water is in the form of groundwater in the pores and fractures within soil, sediment, and rock.
MN Standard Benchmarks
8.3.2.3.1 Describe the location, composition and use of major water reservoirs on the earth, and the transfer of water among them.
8.3.2.3.2 Describe how the water cycle distributes materials and purifies water.
The Essentials
"We forget that the water cycle and the life cycle are one." Jacques Yves Cousteau
NSES Content Standard D Earth and Space Science
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.
NSES Content Standard B Physical Science Standards
Structure and properties of matter
Solids, liquids, and gases differ in the distances and angles between molecules or atoms and therefore the energy that binds them together. In solids the structure is nearly rigid; in liquids molecules or atoms move around each other but do not move apart; and in gases molecules or atoms move almost independently of each other and are mostly far apart.
- AAAS Atlas:
The Physical Environment: Weather and Climate
The Physical Environment: States of Matter
Benchmarks of Science Literacy
By the end of the 8th grade, students should know that
Chapter: 4 (The Physical Setting) Section: B (The Earth)
The earth is mostly rock. Three-fourths of the earth's surface is covered by a relatively thin layer of water (some of it frozen), and the entire planet is surrounded by a relatively thin layer of air. 4B/M2ab*
Everything on or anywhere near the earth is pulled toward the earth's center by gravitational force. 4B/M3
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 oceans. The cycling of water in and out of the atmosphere is a significant aspect of the weather patterns on Earth. 4B/M7*
Fresh water, limited in supply, is essential for some organisms and industrial processes. Water in rivers, lakes, and underground can be depleted or polluted, making it unavailable or unsuitable for life. 4B/M8*
11 (Common Themes) Section: C (Constancy and Change)
The amount of something in a system may stay the same because nothing is entering or leaving the system or because something is being added to the system at the same rate as it is leaving the system. 11C/M11**
Misconceptions
From Beyond Penguins and Polar Bears
- When steam is no longer visible it becomes air.
- Water in an open container is absorbed by the container, disappears, changes into air, or dries up and goes into the air.
- Condensation is when air turns into a liquid.
- Condensation on the outside of a container is water that seeped (or sweated) through the walls of the container.
- Expansion of matter is due to the expansion of the particles rather than increased space between the particles.
- The water cycle involves freezing and melting of water.
- Water only gets evaporated from the ocean or lakes.
- The water cycle only includes rain and snow.
Vignette
In Mr. F's class, he starts the water-cycle unit asking the students to draw a diagram of the water cycle, and to label or describe anything that they can. He allows the students several minutes to do this and circulates the room. Some students have very basic drawings of clouds, the ocean and a mountain stream. Many students have the words precipitation and condensation but aren't really sure what they mean or where they should go. A few students have ground water. Mr. F now has a better understanding of the background knowledge of the students in his classroom and the students have activated the prior knowledge that they have. Throughout the course of the unit, students go back and modify or add to their initial drawing as needed. The evaporation labs cause many students to add the process of evaporation to the surface and in the atmosphere. The precipitation now soaks into the ground, runs off the surface or falls into the ocean on the slowly improving water cycles. Students work together to check each others progress and understanding. At the end of the unit, the students have a messy, but complete water-cycle that is much more complex and helps them to see how they learned more and more over the previous weeks. (Hoffmann, 2011)
Resources
Suggested Labs and Activities
Fog Chamber Make a portable cloud in a bottle. Now you see it; now you don't!
From the Exporatorium Museum (8.3.2.3.1. 8.3.2.3.2)
Fog in A Bottle: A very basic activity demonstrating evaporation and condensation when warm moist air is present. Similar to the "Cloud in a bottle, but does not include the change in pressure needed for the cloud in a bottle. (8.3.2.3.1. 8.3.2.3.2)
Cloud in A Bottle: This common experiment is illustrated here with a video demonstration. (8.3.2.3.1. 8.3.2.3.2)
The Water Cycle Game as presented by the USGS. "Through role-playing as a molecule of water in this game, you can gain a better understanding for the true complexity of the movement of water. Stations are set-up for each of nine different compartments of the water cycle." (8.3.2.3.1. 8.3.2.3.2)
"Follow a Drop Through the Water Cycle" is a good "story" that could be used to introduce the water cycle, or as inspiration to have students write their own journey for a drop of water at the end of a water cycle unit. (8.3.2.3.1. 8.3.2.3.2)
A very basic activity making and observing mini-watersheds. Could be modified to do more inquiry observing different variables such as the amount evaporated from different types of soils, observing different temperatures, etc. (8.3.2.3.1. 8.3.2.3.2)
Project WET has many activities that meet the standards and involve students in active learning. Activities cover a wide variety of water concepts, including the water cycle and some of the special properties of water. Additionally, there is good background material to increase teacher understanding. The full book does require attending a Project WET workshop, but the Minnesota based supplemental book is fully available and contains excellent information and activities as well. Includes link to correlation with the current state standards.(8.3.2.3.1. 8.3.2.3.2)
Instructional Suggestions/options
From NSDL Science Literacy Maps
Students' ideas about conservation of matter, phase changes, clouds, and rain are interrelated and contribute to understanding the water cycle. Students seem to transit a series of stages to understand evaporation. Before they understand that water is converted to an invisible form, they may initially believe that when water evaporates it ceases to exist, or that it changes location but remains a liquid, or that it is transformed into some other perceptible form (fog, steam, droplets, etc.). With special instruction, some students in 5th grade can identify the air as the final location of evaporating water.] Students in 5th grade must accept air as a permanent substance before they can identify the air as the final location of evaporating water. The idea that air is a permanent substance appears to be a challenging concept for upper elementary students.
Students of all ages show a wide range of beliefs about the nature and behavior or particles. They lack an appreciation of the very small size of particles; believe there must be something in the space between particles; have difficulty in appreciating the intrinsic motion of particles in solids, liquids and gases; and have problems in conceptualizing forces between particles. Despite these difficulties, there is some evidence that carefully designed instruction carried out over a long period of time may help middle-school students develop correct ideas about particles.
Before students understand that water is converted to an invisible form, they may initially believe that when water evaporates it ceases to exist, or that it changes location but remains a liquid, or that it is transformed into some other perceptible form (fog, steam, droplets, etc.). With special instruction, some students in 5th grade may be able to identify the air as the final location of evaporating water [11] Students must accept air as a permanent substance before they can identify the air as the final location of evaporating water. For many students, difficulty understanding the existence of water vapor in the atmosphere persists in middle school years. Students can understand rainfall in terms of gravity once they attribute weight to little drops of water (typically in upper elementary grades), but the mechanism through which condensation occurs may not be understood until high school.
As these considerations compiled by AAAS show, while the concepts are presented in 6th grade, they are not necessarily ready to understand them yet at that age. It will be necessary to revisit standard 6.2.1.2. to ensure that the students grasp these important ideas about states of matter and water in particular.
Additional resources
From the USGS, a water cycle page with a good water cycle diagram that can also be printed without labels. While it is definitely exhaustive in covering the information, it seems to be written at a level that might be too high for many 8th grade students to fully understand independently and is very dense and possibly overwhelming. (8.3.2.3.1. 8.3.2.3.2)
A menu of all the water topics covered
A very thorough summary with links for more details about every concept and term
Water-related "posters" available for order or can be printed. These could also be projected onto a smartboard and used interactively in class.
Minnesota specific information
Digital Library of Earth Systems Education DLESE's educational resources include lesson plans, scientific data, visualizations, interactive computer models, and virtual field trips-in short, any web-accessible teaching or learning material.
Vocabulary/Glossary
- Aeration - the process of exposing to air
- atmosphere - the distinct and relatively constant combination gases that surround a planet, on earth there are specific layers with different properties
- condensation - the process in which water vapor in the air is changed into liquid water
- Crust - the outermost layer of the earth
- Deposition - the dropping of materials moved by erosion in a new location
- evaporation - the process by which water changes from a liquid to a gas or vapor
- Filtration - the process of a liquid or gas passing through a porous material which separates suspended materials
- infiltration - flow of water from the land surface into the subsurface.
- oceans - large, interconnected bodies of salt water that cover most of the earth's surface
- phase change - a change in the state of matter
- Pollutants - a substance or energy introduced into the environment that has undesired effects,
- precipitation - water that falls to the ground from the atmosphere as a solid or a liquid
- purification (water cycle) -processes including evaporation, aeration, and filtration remove microorganisms and other particles resulting in more pure water
- runoff -water from precipitation or snow melt that flows across the surface due to gravity
- Sediment - loose materials that have been transported through erosion, including pieces of rock, mineral fragments, and organic matter
- Transpiration - process by which water is evaporated from a plant into the atmosphere from a plant surface, such as leaf pores.
- water cycle - the processes by and reservoirs through which water passes
- water reservoirs - the places on earth where water resides; some reservoirs may have a long residence time and others may be very short
FOSS water module activities include online interactives that explore factors that affect evaporation and an online activity similar to the water cycle game to get a better idea of residence time and the places water may be found. (8.3.2.3.1. 8.3.2.3.2)
This is a very basic interactive overview of the water cycle from the EPA. This has a low-level of detail, but looks at the components separately rather than in the standard picture showing all at once with the "cycle" (8.3.2.3.2)
Dr. Art's Guide to Planet Earth is a book that engages many students. This website is a companion to that book, with three animations on this page related to different levels of understanding the water cycle. (8.3.2.3.1. 8.3.2.3.2)
Social Studies - concerns about fresh water quality and availability are always current events, can be discussed from an ethical standpoint and as a consideration in discussing world population, industry, etc.
Assessment
Assessment of Students
Bibliographic Citation: Keeley, P, Eberle, F, & Farrin, L. (2005). Uncovering student ideas in science: 25 formative assessment probes. Arlington, VA: National Science Teachers Association.
"Ice Cubes in a Bag" asks students to decide whether there will be a change in mass when ice changes to liquid water. It elicits student ideas about conservation of matter in the context of substances and change in state.
"Is It Melting?" asks students to select situations that involve melting as opposed to other physical or chemical changes. It elicits student ideas about the physical process of melting.
"Wet Jeans" asks students to explain why a pair of jeans dry on a clothesline. It elicits student ideas about where water goes right after it evaporates.
Bibliographic Citation: Keeley, P, Eberle, F, & Dorsey, C. (2008). Uncovering student ideas in science: another 25 formative assessment probes. Arlington, VA: National Science Teachers Association.
"What Are Clouds Made Of?" asks students to explain what clouds are made of. It elicits student ideas about clouds.
"Where Did the Water Come From?" asks students to explain why condensation forms on a container of ice cubes. It elicits student ideas about condensation.
"Rainfall" asks students to explain how rain falls from clouds. It elicits student ideas about precipitation.
Additional assessment items available with a free registration from AAAS
Assessment of Teachers
Ground water is often hard for students to understand, the "underground river of water" often leads to misconceptions. How could you present ground water to avoid mental images of long caverns full of water?
Perhaps due to common simplified visual models of the water cycle, many students believe that water evaporates only from bodies of water. How could you help students to discover this is not the case?
Standard 8.3.4.1 addresses land use impacts on the water system. What are some ways this could be integrated into lessons on this standard?
Differentiation
According to Lee & Buxton (2010), a couple of approaches are useful for assisting English Language Learners (ELLs): teach content while fostering language development and draw on the so-called "funds of knowledge," which are students' personal experiences from home or community. For additional details on this see the original NSTA News posting and the official NSTA position statement.
Lee, O., & Buxton, C.A. (2010, April). NSTA Report: Teaching science to English language learners.
English Language Learners. Official NSTA Position Statement.
Water use and water quality are both contemporary issues that could be investigated by students who have mastered the concepts of the standard. Students could investigate this in a variety of ways. There are many online tools for calculating and learning about individual "water footprints" which could be a jumping off point for further study or awareness projects. Additionally, in Minnesota many students have easily accessible bodies of water in their own areas. Students could research their own water supply, from source to tap or identify potential pollutants that may be entering the waterways and consider solutions.
The website has many for specific classroom suggestions for SpEd, ELL
Students with disabilities. Official NSTA Position Statement.
Many of the concepts of the water cycle may be familiar from earlier classes and personal experience. Using a variety of teaching methods will increase the understanding of all students. There are key vocabulary terms that are necessary for explaining and that are part of the standards that special attention needs to be paid to.
Parents/Admin
Administrators
A classroom working on a water cycle unit will contain a variety of representations of the process, as students may be making their own visual representations. There should be some activities where the students are moving around the room, modeling both the movement of water through various reservoirs, but also the movement of water molecules as they change states. Key vocabulary words should be on display and in use by the students.
Links to sites referred to can be provided online to encourage students to review and explain what they are learning about the water cycle to their families. Understanding how the water cycle affects their everyday life and how their lives affect the water cycle may make it more relevant and increase understanding and interest.