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Content Benchmark E.8.A.2
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Earth Science
Atmospheric Process and Water Cycle
Solar System and Universe
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Nature of Science (NOS)
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Physical Science

Students know how the processes involved in the water cycle affect climatic patterns. E/S

You probably already know that water is an important part of our lives.  We drink it, cook with it, water our plants with it, and bathe with it.  Indeed, our bodies are approximately 60% water.  Earth is called both “the water planet” and “the blue planet” because of its’ vast amounts of water.  While space exploration may discover traces of water on other planets or moons in our solar system, no other body in the solar system has the water resources that Earth has.  Water on this planet is stored in the atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and as groundwater.  But did you know that the components of every water molecule on Earth today are over 4 billion years old?  This is because water evaporates (from the surface of water bodies and is released by plants and animals through photosynthesis and respiration), condenses in the atmosphere, falls as precipitation, soaks into the ground, is taken up by plants and animals and runs off into rivers, lakes and oceans over and over again in a process called the water cycle. And, as energy flows into and out of water during its passage through the water cycle, Earth’s climate patterns are affected.  Indeed, all of Earth’s many climate types are caused by just two things – the precipitation of water, and temperature (which is dominated by water as it distributes heat over the planet).

There is a great deal of debate about global warming and climate change in today’s world.  It is a complex issue, complicated by many factors.  To understand climatic patterns (and begin to understand how they might change), one must understand the water cycle, the difference between weather and climate, how convection drives the water cycle and therefore weather and climate, and that water in the atmosphere has a significant role as a greenhouse gas. 

The Water Cycle
Water (H2O) is an amazing molecule.  It is the only substance that exists in all three physical states of matter (solid, liquid, gas) under natural conditions on Earth (ice/snow, water, water vapor).  Energy from the Sun, in the form of heat, drives the water cycle.  When heat energy is added to ice, it melts; a change of state from solid to liquid.  When heat energy is added to water, it evaporates; a change of state from liquid to gas.  But what about the reverse?  If heat energy is removed from water vapor, it condenses; a change of state from gas to liquid.  If heat energy is removed from water, it freezes; a change of state from liquid to solid.  These changes are completely reversible and water can go back and forth between different stages in the water cycle.  The basic stages of the water cycle are evaporation (liquid to gas), condensation (gas to liquid), and precipitation (falling of liquid or solid water to the surface).  Accumulation (runoff from the surface to lakes, streams and oceans, and subsurface runoff – water soaking into the Earth) and transpiration (water released by plants through photosynthesis) are also components of the water cycle.  Transpiration of water from plants accounts for about 10% of water vapor in the atmosphere.

These changes in state for the water molecule occur at temperatures that are fairly far apart:  pure water freezes/melts at 0°C and condenses/evaporates at 100°C.  The water molecule has a high specific heat, which means that it takes a relatively large amount of energy to cause it to change state.  This means that when it does change state, a large amount of energy is either released to, or absorbed from, the atmosphere and or surrounding environment.  Thus, water and its’ changes of state provides the engine that drives the temperature on Earth.  The energy exchange between the water in the water cycle and the surrounding atmosphere drives the weather of a local area and ultimately, the climate of a larger region.

 Figure 1. The Water Cycle

For more information about the water cycle, go to

Further information about the physical states of water can be found in
MS TIPS Benchmark E.8.A.3

Weather and Climate
In short, weather can be defined as the atmospheric conditions locally, or in a small geographic area, which can change day to day.  Examples of weather include thunderstorms, a drizzle, or a nice sunny day.  Climate is the overall pattern of weather for an area, and is defined by predictable weather events over a long period of time, usually 30 years or more.  The continental United States is commonly considered to have seven climate regions.  They are the Northwest region (#1), the High Plains region (#2), the Midwest/Ohio Valley region (#3), the New England/Mid Atlantic region (#4), the Southeast region (#5), the Southern region (#6), and the Southwest region (#7).

Figure 2. Climate regions of the U.S.

For more information about climate and global change, go to

For more detail about weather and climate refer to MS TIPS Benchmark E.8.A.5 and
MS TIPS Benchmark E.8.A.6

Convection in the Water Cycle, Weather, and Climate
The Sun is the primary source of heat energy in Earth’s atmosphere.  But, because the Earth is spherical, the heat energy reaching Earth varies at different latitudes.

Figure 2
Figure 3. Rays from the sun to the earth. The area lit by the sun's ray is
greater at A than at B. So, the solar energy falling on a unit area
is greater at the tropics than at higher latitudes.
(from )

Thus the rate of evaporation is greater at equatorial latitudes, and more water vapor is put into the air.  Additionally, air molecules, and water vapor molecules in the air, absorb more heat energy at the equator than at the poles.  This increases their kinetic energy, or energy of movement, and they move faster and further apart from each other.  This decreases the density of the air at the surface near the equator, and the air and water molecules rise.  Water also has less molar mass than air (~18g/mol vs. ~29g/mol), so when air becomes more saturated with water vapor, the resulting mass is lessened. The air higher in the atmosphere is cooler.  As the heated and more energetic molecules rise above the surface, they release their heat energy to the cooler air further above the surface and further from the equator.  As they release energy, their kinetic energy is reduced, the molecules move closer together, and the air mass gets more dense.  Two things then occur.  The more dense air sinks back down toward the surface of the Earth, and the water vapor molecules can condense to form clouds. During this process pressure differences cause winds. Rising air decreases pressure at the surface of the Earth, so that surrounding surface air flows in.  Falling air increases pressure at the surface, so air is forced out. This is a convection cell.  On a non-rotating Earth, there would be two convection cells – one in each hemisphere. This cycle of heat collection and transfer is called convection and is a continuous process, thus setting up a circular pattern of heat flow between the surface and the upper atmosphere, and between the equator and the poles.

Figure 4.  Convection Cells on a non-rotating Earth

But, because of Earth’s rotation, the two convection cells are split apart.  The air flow in the northern cell is deflected to the right (as you look down on the North Pole from above).  The process is reversed in the southern cell.  The deflection is caused by the Coriolis Force.  Three major convective cells (Hadley Cells) are formed in each hemisphere, with corresponding lows and highs at the surface, and low altitude winds, all of which contribute to weather, climate, and heat distribution on Earth.

Figure 5. Idealized, three cell atmospheric convection in a rotating Earth.

In addition to the winds generated by convection, the Jet Stream is a global high-altitude wind that blows at speeds up to 350 kilometers per hour, and between 6,000-12,000 meters above Earth’s surface.  It blows from west to east in one or more mid-latitude bands, both in the northern and southern hemispheres.  The Jet Stream is strongest during the winter months because the differential in pressure between cold air masses at the poles and warm air masses at the equator are the greatest.  In the summer, when the differential is less, the strength of the Jet Stream is less.  The location of the Jet Stream can affect weather in an area because it can “steer” weather systems.  Airline pilots flying east will try to ride the jet stream, while those flying west will try to avoid it.

Figure 6.  Jet stream.

For additional information on Earth’s atmospheric circulation visit

For more about atmospheric temperature differences and convection, see

Further detail about latitude and incident solar energy can be found in the
MS TIPS Benchmark E.8.A.1

For more information concerning the role of water in Earth’s weather and climate refer to MS TIPS Benchmark E.8.A.4

The Greenhouse Effect
The Earth receives less than a billionth of the sun’s energy output.  Although this seems paltry, it is still plenty to power all life processes on Earth.  However, these processes are highly dependant on the presence of the atmosphere, and if there were no atmosphere on Earth, conditions would not be very conducive to life.  In fact, temperatures on the surface would be like those on the moon, which has no atmosphere, and would range from -184°C (-300°F) in the shade to an average of 101°C (214°F) in the sun.  But because Earth does have an atmosphere, temperatures are held fairly constant, from night to day, without extreme temperature swings, rather like a greenhouse.  How does this process work?  Basically, incident sunlight, also known as insolation, on Earth is either absorbed or is bounced back out into space. Sunlight is reflected off snow, clouds and other light colored surfaces, and absorbed by darker colored surfaces and water. The amount of reflectivity of a surface is known as its Albedo.  About 30% of the insolation that reaches the Earth bounces back due to the Albedo Effect. Clouds in the atmosphere also contribute to Earth’s Albedo.  The amount of insolation received by the Earth and the amount of heat energy lost to space are in relative balance.  This causes temperatures on Earth to remain fairly constant and livable.  This complicated process is called the Greenhouse Effect.  It is a natural process and without it Earth would be too hot, or too cold, and barren.

Figure 7.  The Greenhouse Effect

Water in the Atmosphere
Water can exist on Earth and in the atmosphere in any of its three states – solid, liquid, or gas.  It can be found in the atmosphere as water vapor, clouds, and ice crystals.  Clouds have an effect on how much incident solar energy reaches the surface, and water vapor has a great deal to do with the greenhouse effect.

Further information about the physical states of water can be found in the
MS TIPS Benchmark E.8.A.3

Water as a Greenhouse Gas
The balance between sun energy that is trapped at the surface and in the atmosphere and the energy that is subsequently released back into space is delicate.  In particular, gas molecules like carbon dioxide and water vapor in the atmosphere can hold a great deal of energy and keep heat in the atmosphere.  These are called Greenhouse Gases. Water vapor is a naturally occurring greenhouse gas and accounts for the largest percentage of the greenhouse effect.  The amount of water vapor in Earth’s atmosphere is relatively constant, and is not directly affected by human activity.  But, if an increase in the concentrations of other greenhouse gases, like carbon dioxide, occurred, it is hypothesized that they would act to increase the greenhouse effect and raise temperatures at the surface. This increase in surface temperatures would likely cause additional amounts of water vapor to be put into the atmosphere.  The increased water vapor in turn leads to an increase in the greenhouse effect and thus a further increase in temperature; the increase in temperature leads to still further increase in atmospheric water vapor; and the feedback cycle continues until equilibrium is reached.

For additional information on water in the atmosphere, including the weight of clouds, see

Further information about the role of water as a greenhouse gas can be found in
MS TIPS Benchmark E.8.A.3

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Content Benchmark E.8.A.2

Students know how the processes involved in the water cycle affect climatic patterns. E/S

Common misconceptions associated with this benchmark

1.  Middle School students often do not completely understand where water vapor goes when water evaporates or how liquid water can appear out of thin air when water vapor condenses.

Many students’ concepts of evaporation and condensation appear to be dependent upon three notions – conservation of matter, the concept of atoms or molecules, and the understanding that air contains particles we cannot see.  By middle school, students should start linking these notions to the water cycle and the role of evaporation and condensation in the promotion of energy flow in the atmosphere.  However, if direct instruction in these ideas is not provided, students may encounter some stumbling blocks.  For example, the water cycle is oversimplified by diagrams in texts that show arrows from bodies of water directly up to clouds in the atmosphere. Because water vapor cannot be seen, students may say that it either becomes clouds, or it just disappears. In fact, matter cannot be destroyed, and a change in state from a liquid to a gas is a physical change involving energy transfer.  Students may say, incorrectly, that water appearing on a glass of ice water or a can of soda has “leaked through.” This inability to comprehend the existence of a state of matter completely ignores the role of water vapor and heat flow in the atmosphere, a critical part of the science of this standard.
For information concerning this misconception see Project 2061, this site discusses the need for nation wide standards and what is appropriate content knowledge for students to know, by grade level.

The following site discusses “Student Difficulties and Misconceptions in Science.”

Common misconceptions are discussed and their possible causes.

Microscopic view of evaporation and condensation

Details on the water cycle

2. Students may incorrectly believe that climate change is all man-caused.

Due to the many negative references to climate change amid fears of global warming, students may not realize that the evolution/change of climate on Earth is a dynamic process, which may be caused by natural events, such as volcanoes, changes in Earth’s precession, and changes in the sun’s output, not to mention large-scale tectonic movements.

Information concerning natural vs. manmade climate change can be found at the following sites.

This site discusses Weather vs. Climate and may help the students make that distinction.

For an article that discusses recent findings that natural climate changes may be larger than previously thought and have occurred in recent times, visit

Further background on “What is climate change?” and factors that influence climate change see

For a detailed discussion on climate and weather in student friendly terms, go to

3. Students may not fully understand the dynamics of atmospheric convection and energy transfer.

Students may mistakenly believe that temperatures on Earth are mostly “even” because the Earth receives the same amount of sunlight at all latitudes.  This is incorrect and students need to realize that the equator receives the bulk of incident solar radiation.  This, in turn, leads to the formation of global convection cells, which serve to transfer heat energy from the equator toward both poles.  In addition, when the Earth’s rotation is added to the process, students may have a difficult time visualizing the deflection of the cells, the formation of areas of high and low pressure, and the development of global winds.

Why do locations at higher latitudes receive less sunlight?

Wind and Global Wind Systems

4. Students may not realize that water vapor is a major greenhouse gas, and that the Greenhouse effect is a natural and necessary phenomenon for life on Earth.

Due to the ubiquitous use of the phrase “greenhouse effect” or “greenhouse gas” in connection with accelerated global warming, students may associate it negatively with climate change.  Instead, life on Earth could not exist without a greenhouse effect.  The fact that water vapor is an important gas that makes up over 50% of the greenhouse gases in the atmosphere is one that is rarely addressed.  However, it is necessary to understand the role of water vapor in the atmosphere for convection and heat transfer, and in the formation of an environment on Earth conducive to life.

See NOAA FAQ’s on Greenhouse Gases at

For greater detail on understanding greenhouse gases, visit

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Content Benchmark E.8.A.2

Students know how the processes involved in the water cycle affect climatic patterns. E/S

Sample Test Questions

1st Item Specification: Understand the movement of water through the water cycle.

Depth of Knowledge Level 1

  1. Which part of the water cycle leads to the development of clouds?
    1. Condensation
    2. Infiltration
    3. Precipitation
    4. Runoff
  1. Water moves from oceans, rivers and lakes to air vapor through
    1. condensation.
    2. runoff.
    3. precipitation.
    4. evaporation.

Depth of Knowledge Level 2

  1. For condensation to occur, water vapor must
    1. heat up and turn into liquid.
    2. cool down and turn into liquid.
    3. cool down and evaporate into a gas.
    4. heat up and evaporate into a gas.
  1. How are the water cycle processes of runoff and infiltration different? Runoff moves
    1. downhill whereas infiltration moves through bedrock.
    2. uphill whereas infiltration moves over bedrock.
    3. downhill and infiltration moves uphill.
    4. uphill whereas infiltration moves downhill.

2nd Item Specification: Students understand the difference between weather and climate.

Depth of Knowledge Level 1

  1. Which of the following climate factors is also a part of the water cycle?
    1. Temperature.
    2. Precipitation.
    3. Infiltration.
    4. Evaporation.
  1. A region’s climate is determined by the temperatures and amount of precipitation averaged over which of the following time intervals?
    1. 1 week
    2. 1 year
    3. 30 years
    4. 48 hours

Depth of Knowledge Level 2

  1. Understanding the climate for a typical region allows a person to
    1. anticipate what the weather is likely to be in a given month.
    2. accurately predict the weather weeks in advance.
    3. not be certain what the weather will be in a given month.
    4. know the daily high temperature for the next several days.

3rd Item Specification: Students will understand the role convection has in the water cycle, weather and climate.

Depth of Knowledge Level 1

  1. Convection in the oceans and atmosphere is a result of the difference in
    1.  mass.
    2.  temperature.
    3.  weight.
    4.  volume.
  1. As the sun heats up the surface of the ocean, convection currents can increase
    1. evaporation.
    2. infiltration.
    3. precipitation.
    4. condensation

Depth of Knowledge Level 2

  1. During temperature inversion, a cool air mass is located below a warm air mass. What would be impact on the weather?
    1. The cool air mass will rapidly rise and result in thunderstorms.
    2. The air masses would stall and could lead to the development of smog.
    3. The warm air will sink below the cold air through the process of convection.  
    4. The cool air will rise above the warm air through the process of convection.

4th Item Specification: Describe water in the atmosphere as water vapor, clouds, ice crystals and their role as a greenhouse gas.

Depth of Knowledge Level 1

  1. Water suspended in high altitude clouds is likely to be in the form of
    1. water vapor.
    2. ice crystals.
    3. snow.
    4. rain.
  1. Which of the following is considered a greenhouse gas?
    1. Carbon monoxide
    2. Water vapor
    3. Ammonia
    4. Argon

Depth of Knowledge Level 2

  1. Increased cloudiness would cause average daytime temperatures to
    1. increase because water has a high specific heat.
    2. decrease because water has a low specific heat.
    3. decrease as clouds reflect solar radiation.
    4. increase as clouds are the main source of precipitation.
  1. Compared to an evening with clear skies, cloudy conditions in the evening have what effect on the overnight temperatures? The clouds cause a(n)
    1. decrease in solar radiation which will cause the temperatures to remain higher than on a clear night.
    2. increase in solar radiation which will cause the temperatures to be higher than on a clear night.
    3. decrease in the overnight temperature because the clouds block the moonlight.
    4. increase in the temperature because there is a greater chance of precipitation.

Constructed Response E.8.A.2

Use the following data table showing the percentages of greenhouse gases in the atmosphere to answer the following question.

Greenhouse Gases in the Atmosphere

Type of Greenhouse Gas

 Percent of Total

 Water vapor


 Carbon Dioxide (CO2)


 Methane (CH4)


Nitrous oxide (N2O)


 CFC's (and other misc. gases)




(Modified from

Provide an explanation of how an increase in the amount of atmospheric carbon dioxide would affect the amount of water vapor in the atmosphere.  What effect might this have on global warming?

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Content Benchmark E.8.A.2

Students know the processes involved in the water cycle affect climatic patterns. E/S

Answers to Sample Test Questions

  1. A, DOK Level 1
  2. D, DOK Level 1
  3. B, DOK Level 2
  4. A, DOK Level 2
  5. B, DOK Level 1
  6. C, DOK Level 1
  7. A, DOK Level 2
  8. B, DOK Level 1
  9. A, DOK Level 1
  10. B, DOK Level 2
  11. B, DOK Level 1
  12. B, DOK Level 1
  13. C, DOK Level 2
  14. A, DOK Level 2

Constructed Response E.8.A.2 Score Rubric:

3 points

Response addresses all parts of the question clearly and correctly.

The amount of carbon dioxide in the atmosphere is significantly lower than the amount of water vapor. If amount of carbon dioxide increases, then this could cause an increase in atmospheric temperature which could cause a greater amount of evaporation to occur, adding additional water vapor to the atmosphere.  As water vapor is the most abundant greenhouse gas, this could in turn cause global temperatures to increase. If temperatures increase, then evaporation could increase which could result in what is known as a “positive feedback loop”.

2 points

Response addresses all parts of the question and includes only minor errors.

1 point

Response does not address all parts of the question. 

0 points

The response is totally incorrect or no response provided. 

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Content Benchmark E.8.A.2

Students know how the processes involved in the water cycle affect climatic patterns. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. The EPA Climate Change Kids Site

The kids page focuses on the science and impacts of global warming or climate change, and on actions that help address climate change.  It includes sections on weather & climate, greenhouse effect, and other topics dealing with climate change.  Games, links, animations, and teacher resources are also present.
The site can be found at

2. USGS Water Science for Schools:  Water Cycle

This interactive site allows students to click on the water cycle and learn about each component:  stream flow, surface runoff, freshwater storage, ground-water discharge, ground-water storage, infiltration, precipitation, snowmelt, runoff to streams, springs, water in the atmosphere, evaporation, evapotranspiration, condensation, sublimation, ice and snow, oceans.  There is a lot of information here, including printable diagrams, with and without labels, and links to other water cycle sites.

Access the site at

 3. TeacherPlanet – The Water Cycle

TeacherPlanet features over 350 theme based resource pages.  This link to the Water Cycle theme includes lesson plans, activities, worksheets, webquests, online activities and games such as Concentration, Flash Cards, and Matching.  There is truly an amazing amount of resources for teacher and student here.

This site is found at

4. Climate and Weather

Climate is an interactive lesson that teaches kids about climate, the historical record and   description of average daily and seasonal weather events in a certain region. It explains climate so that kids can understand it, and how it relates to weather. It also let students explore various regional climates in the United States, offers an online quiz about the regional climates, and provides various climate-related activities for students to do.

Find this resource at

For more information about the Coriolis Effect and wind

5. Research and investigate weather-related phenomena

The goal of the site is to provide middle school science students and teachers with research and investigation experiences using on-line resources. You can download needed software and the Student Activity Books that complement the on-line science lessons. There is a link with information that includes lesson objectives, interdisciplinary uses, NSTA and AAAS standards, and teacher preparation material.  Links include Greenhouse Effect, Atmosphere, Storms, El Nino, Fisheries, Great Lakes, and Oceans.

Follow the link for the site
For a Greenhouse Effect Activity, visit

6. Atmospheric Processes – Convection

This site provides information and graphics about convection in fluids – liquids and gases.  It includes two laboratory activities.  One, “Currents in Water”, involves heating water and making observations concerning the convection currents set up. The second, “Air as a Fluid”, utilizes a mixture of vinegar and baking soda flowing toward a lit candle and extinguishing it. 

To access these activities, visit

7. Geography for kids – Convection, Climate, Atmosphere

First a definition... What the heck is a climate? Is it weather? Is it the rain? Is it a hot day in August? Yes, yes and yes, but only in one place at a time.  The following links provide students with more information about Earth’s atmosphere, the convection process, and climate vs. weather.   Multimedia features, quizzes, and additional links are provided.  These pages are very kid friendly.

To access this site visit

To access a link about the atmosphere visit

8. Teacher’s Domain – a free resource with lots of links

What are the properties of water when it is a liquid, solid, or gas? What are the different types of clouds? What processes make up the water cycle? What can ice cores from Greenland tell us about Earth's climatic history? How does the atmosphere change as altitude increases? How do we predict the intensity of a hurricane? Explore these questions and more in this collection of Water Cycle, Weather, and Climate resources.

Many links about the atmosphere, jet stream, weather, etc. from Teachers Domain can be
found at

9. JetStream Learning Lessons

This collection of 35 links with lessons about the atmosphere, the ocean, global circulation, synoptic meteorology, thunderstorms, lightening, and weather on the web also provides information about heat transfer and convection.  Indeed, there are many, many links to other websites of similar content.

Find these lessons and links at

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Support Pages

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Sample Questions:
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Intervention Strategies & Resources:
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Benchmark Related Vocabulary

Average precipitation
Average temperature
Water cycle