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Water Cycle

What is the water cycle.

Water cycle, also known as the hydrologic cycle, involves a series of stages that show the continuous movement and interchange of water between its three phases – solid, liquid, and gas, in the earth’s atmosphere. The sun acts as the primary source of energy that powers   the   water cycle on earth. Bernard Palissy discovered the modern theory of the water cycle in 1580 CE.

Steps of the Water Cycle: How does it Work

1. Change from Liquid to Gaseous Phase – Evaporation and Transpiration

The heat of the sun causes water from the surface of water bodies such as oceans, streams, and lakes to evaporate into water vapor in the atmosphere. Plants also contribute to the water cycle when water gets evaporated from the aerial parts of the plant , such as leaves and stems by the process of transpiration.

2. Change from Solid to Gaseous Phase – Sublimation

Due to dry winds, low humidity, and low air pressure, snow present on the mountains change directly into water vapor, bypassing the liquid phase by a process known as sublimation.

3. Change from Gaseous to Liquid Phase – Condensation

The invisible water vapor formed through evaporation, transpiration, and sublimation rises through the atmosphere, while cool air rushes to take its place. This is the process of condensation that allows water vapor to transform back into liquid, which is then stored in the form of clouds.

Sometimes, a sudden drop in atmospheric temperature helps the water vapors to condense into tiny droplets of water that remain suspended in the air. These suspended water droplets get mixed with bits of dust in the air, resulting in fog.

4. Change from Gaseous to Liquid and Solid Phase – Precipitation and Deposition         

Wind movements cause the water-laden clouds   to collide and fall back on the earth’s surface through precipitation, simply known as rain. The water that evaporated in the first stage thus returns into different water bodies on the earth’s surface, including the ocean, rivers, ponds, and lakes. In regions with extremely cold climate with sub-zero temperatures, the water vapor changes directly into frost and snow bypassing the liquid phase, causing snowfall in high altitudes by a process known as the deposition. 

5. Return of the water back into the underground reserve – Runoff, Infiltration, Percolation, and Collection

The water that falls back on the earth’s surface moves between the layers of soil and rocks and is accumulated as the underground water reserves known as aquifers. This process is further assisted by earthquakes, which help the underground water to reach the mantle of the earth. Some amount of precipitated water flows down the sides of mountains and hills to reach the water bodies, which again evaporates into the atmosphere. During volcanic eruptions, the underground water returns to the surface of the earth, where it mixes with the surface water bodies in order to continue the cycle.

Video: Water Cycle Explained

Why is the water cycle important.

The most crucial and direct impacts of the above process on earth include:

• Making fresh water available to plants and animals, including humans, by purifying the groundwater on earth. During the water cycle, the water evaporates, leaving behind all the sediments and other dust particles. Similarly, for the sustenance of marine life, the saline range of all salt water bodies is kept within a certain permissible limit through infiltration. 
• Allowing even distribution of water on all surfaces of the earth. Water is temporarily stored as clouds in the atmosphere, whereas surface water bodies such as rivers and oceans, together with underground water, form the major permanent water reserves. 
• Causing a cooling effect on earth due to evaporation of water from surface water bodies, which help to form clouds that eventually precipitate down in the form of rain. This way water cycle affects the weather and climate of the earth.
• Ensuring some other biogeochemical cycles , including those concerning oxygen and phosphorus, to continue in nature.
• Cleaning the atmosphere by taking-away dust particles, shoot, and bacteria , thus acting as a means to purify the air we breathe.

Human Impact on Water Cycle

Human activities adversely affect the water cycle in the two following ways:

a) Deforestation : Plants play an important role in the water cycle by preventing soil erosion and thus helps to increase the groundwater level of the earth. Also, plants contribute by absorbing water from the soil, which is then released back to the atmosphere during transpiration. Deforestation adversely affects both the above processes, thus breaking the flow of the water cycle.

b) Pollution : Burning of fossil fuels acts as the major source of air pollution releasing toxic gases into the atmosphere, leading to the formation of smog and acid rain . Water from farmlands run off to the nearest water bodies carrying chemicals such as insecticides and pesticides along with them, thus causing water pollution. The presence of excessive contaminants in the atmosphere and water bodies decreases the evaporation and condensation on earth, thus adversely affecting the water cycle.

Ans. Cellular respiration is the process by which organisms take up oxygen in order to breathe and digest food. Water is utilized for breaking large molecules that release energy in the form of ATP , while in a subsequent step the water molecules are released back into the cell, which in turn returns to the atmosphere, thus affecting the water cycle.

Ans. Rivers contain more water than streams and thus contribute more to the formation of water vapor through evaporation compared to a stream.

• Water Cycle – Britannica.com
• The Water Cycle – Khanacademy.org
• Water Cycle – Noaa.gov
• What Is The Hydrologic Cycle? – Worldatlas.com
• What is the Water Cycle? – Earth.com
• The Water Cycle – Coastgis.marsci.uga.edu

Article was last reviewed on Wednesday, May 17, 2023

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One response to “Water Cycle”

The first part of the water cycle is of course evaporation and transportation, but I don’t want to focus on that, I want to focus on the 2nd step which is sublimation. Sublimation is when snow or hail, or sleet falls down on a mountain and it quickly turns into water vapor by passing the liquid phase.Now lets skip to the last phase which is RIPC

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• Biology Article

Water Cycle

What is the Water Cycle? Water Cycle Diagram Stages of Water Cycle Implications of Water Cycle Frequently Asked Questions

What is the Water Cycle?

Water Cycle Diagram

During this process, water changes its state from one phase to another, but the total number of water particles remains the same. In other words, if it were possible to collect and boil 100 gms of water, it will still retain a mass of 100 gms as steam. Likewise, if 100 gms of steam is collected and condensed, the resultant water would still weight 100 gms.

Water changes its state through a variety of processes from evaporation, melting and freezing, to sublimation, condensation, and deposition. All these changes require the application of energy.

Stages of Water Cycle

There are many processes involved in the movement of water apart from the major steps given in the above water cycle diagram. Listed below are different stages of the water cycle.

1. Evaporation

The sun is the ultimate source of energy, and it powers most of the evaporation that occurs on earth. Evaporation generally happens when water molecules at the surface of water bodies become excited and rise into the air. These molecules with the highest kinetic energy accumulate into water vapour clouds. Evaporation usually takes place below the boiling point of water. Another process called evapotranspiration occurs when evaporation occurs through the leaves of plants. This process contributes to a large percentage of water in the atmosphere.

2. Sublimation

Sublimation occurs when snow or ice changes directly into water vapour without becoming water. It usually occurs as a result of dry winds and low humidity. Sublimation can be observed on mountain peaks, where the air pressure is quite low. The low air pressure helps to sublimate the snow into water vapour as less energy is utilised in the process. Another example of sublimation is the phase where fog bellows from dry ice. On earth, the primary source of sublimation is from the ice sheets covering the poles of the earth.

3. Condensation

The water vapour that accumulated in the atmosphere eventually cools down due to the low temperatures found at high altitudes. These vapours become tiny droplets of water and ice, eventually coming together to form clouds.

4. Precipitation

Above 0 degrees centigrade, the vapours will condense into water droplets. However, it cannot condense without dust or other impurities. Hence, water vapours attach itself on to the particle’s surface. When enough droplets merge, it falls out of the clouds and on to the ground below. This process is called precipitation (or rainfall). In particularly cold weather or extremely low air pressure, the water droplets freeze and fall as snow or hail.

5. Infiltration

Rainwater gets absorbed into the ground through the process of infiltration. The level of absorption varies based on the material the water has seeped into. For instance, rocks will retain comparatively less water than soil. Groundwater can either follows streams or rivers. But sometimes, it might just sink deeper, forming aquifers.

If the water from rainfall does not form aquifers, it follows gravity, often flowing down the sides of mountains and hills; eventually forming rivers. This process is called runoff. In colder regions, icecaps form when the amount of snowfall is faster than the rate of evaporation or sublimation. The biggest icecaps on earth are found at the poles.

All the steps mentioned above occur cyclically with neither a fixed beginning nor an end.

Also Read:  Back to the Oceans

Implications of Water Cycle

• The water cycle has a tremendous impact on the climate. For instance, the greenhouse effect will cause a rise in temperature. Without the evaporative cooling effect of the water cycle, the temperature on earth would rise drastically.
• The water cycle is also an integral part of other biogeochemical cycles.
• Water cycle affects all life processes on earth.
• The water cycle is also known the clean the air. For instance, during the process of precipitation, water vapours have to attach themselves on to particles of dust. In polluted cities, the raindrops, apart from picking up dust, also pick up water-soluble gas and pollutants as they fall from the clouds. Raindrops are also known to pick up biological agents such as bacteria and industrial soot particles and smoke.

Read more about the water cycle with diagram by registering @  BYJU’S Biology

• Biogeochemical cycles
• Oxygen Cycle
• Carbon Cycle
• Nitrogen Cycle

Frequently Asked Questions

What are the major 4 steps in the water cycle.

The major 4 steps are evaporation of water, then condensation, precipitation and collection. The sun evaporates water sources and contributes to the formation of water vapor. These water vapour accumulate in the atmosphere as clouds. The vapours condense into water droplets and when enough droplets merge, it falls out of the clouds as rain.

What is the difference between evaporation and condensation?

Evaporation is a process by which water changes into water vapour. Condensation is an opposite process by which water vapour is converted into tiny droplets of water.

Why is water cycle important?

Water cycle has a huge impact on determining the global climate. It is also an integral part of other biogeochemical cycles. It affects all life processes on Earth either directly or indirectly.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

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water cycle

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• NASA Science - Water Cycle
• U.S. Geological Survey - The Water Cycle
• Chemistry Libretexts - Water Cycle
• Northwest River Forecast Center - The Water Cycle
• Northwest River Forecast Center - Hydrologic Cycle
• NeoK12 - Educational Videos and Games for School Kids - Water Cycle
• Pennsylvania State University - Department of Energy and Mineral Engineering - Understanding water cycle
• UCAR Center for Science Education - The Water Cycle
• water cycle - Children's Encyclopedia (Ages 8-11)
• water cycle - Student Encyclopedia (Ages 11 and up)

water cycle , cycle that involves the continuous circulation of water in the Earth - atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation , transpiration , condensation , precipitation , and runoff . Although the total amount of water within the cycle remains essentially constant, its distribution among the various processes is continually changing.

A brief treatment of the water cycle follows. For full treatment, see hydrosphere: The water cycle .

Evaporation , one of the major processes in the cycle, is the transfer of water from the surface of the Earth to the atmosphere. By evaporation, water in the liquid state is transferred to the gaseous , or vapour, state. This transfer occurs when some molecules in a water mass have attained sufficient kinetic energy to eject themselves from the water surface. The main factors affecting evaporation are temperature , humidity , wind speed, and solar radiation . The direct measurement of evaporation, though desirable, is difficult and possible only at point locations. The principal source of water vapour is the oceans , but evaporation also occurs in soils , snow , and ice . Evaporation from snow and ice, the direct conversion from solid to vapour, is known as sublimation. Transpiration is the evaporation of water through minute pores, or stomata, in the leaves of plants . For practical purposes, transpiration and the evaporation from all water, soils, snow, ice, vegetation, and other surfaces are lumped together and called evapotranspiration , or total evaporation.

Water vapour is the primary form of atmospheric moisture. Although its storage in the atmosphere is comparatively small, water vapour is extremely important in forming the moisture supply for dew , frost , fog , clouds , and precipitation. Practically all water vapour in the atmosphere is confined to the troposphere (the region below 6 to 8 miles [10 to 13 km] altitude).

The transition process from the vapour state to the liquid state is called condensation . Condensation may take place as soon as the air contains more water vapour than it can receive from a free water surface through evaporation at the prevailing temperature. This condition occurs as the consequence of either cooling or the mixing of air masses of different temperatures. By condensation, water vapour in the atmosphere is released to form precipitation .

Precipitation that falls to the Earth is distributed in four main ways: some is returned to the atmosphere by evaporation, some may be intercepted by vegetation and then evaporated from the surface of leaves , some percolates into the soil by infiltration, and the remainder flows directly as surface runoff into the sea. Some of the infiltrated precipitation may later percolate into streams as groundwater runoff. Direct measurement of runoff is made by stream gauges and plotted against time on hydrographs.

Most groundwater is derived from precipitation that has percolated through the soil. Groundwater flow rates, compared with those of surface water, are very slow and variable, ranging from a few millimetres to a few metres a day. Groundwater movement is studied by tracer techniques and remote sensing.

Ice also plays a role in the water cycle. Ice and snow on the Earth’s surface occur in various forms such as frost, sea ice , and glacier ice. When soil moisture freezes, ice also occurs beneath the Earth’s surface, forming permafrost in tundra climates . About 18,000 years ago glaciers and ice caps covered approximately one-third of the Earth’s land surface. Today about 12 percent of the land surface remains covered by ice masses.

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Water cycle

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Keep exploring

Find even more resources on the water cycle in our searchable resource database.

The water cycle is often taught as a simple circular cycle of evaporation, condensation, and precipitation. Although this can be a useful model, the reality is much more complicated. The paths and influences of water through Earth’s ecosystems are extremely complex and not completely understood. NOAA is striving to expand understanding of the water cycle at global to local scales to improve our ability to forecast weather, climate, water resources, and ecosystem health.

The water cycle. (Image credit: Dennis Cain/NWS)

The water cycle on Earth

Water is essential to life on Earth. In its three phases (solid, liquid, and gas), water ties together the major parts of the Earth’s climate system — air, clouds, the ocean, lakes, vegetation, snowpack offsite link , and glaciers offsite link .

The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow. Water in different phases moves through the atmosphere (transportation). Liquid water flows across land (runoff), into the ground (infiltration and percolation), and through the ground (groundwater). Groundwater moves into plants (plant uptake) and evaporates from plants into the atmosphere (transpiration). Solid ice and snow can turn directly into gas (sublimation). The opposite can also take place when water vapor becomes solid (deposition).

See how NOAA science is safeguarding lives, economies, and a healthy water supply.

Water, society, and ecology

Water influences the intensity of climate variability and change. It is the key part of extreme events such as drought and floods . Its abundance and timely delivery are critical for meeting the needs of society and ecosystems.

Humans use water for drinking, industrial applications, irrigating agriculture, hydropower, waste disposal, and recreation. It is important that water sources are protected both for human uses and ecosystem health. In many areas, water supplies are being depleted because of population growth, pollution, and development. These stresses have been made worse by climate variations and changes that affect the hydrologic cycle.

A series of atmospheric rivers starting in late December 2022 through mid-January 2023 dropped feet of rain and snow across California and other parts of the West Coast.

Water and climate change

Climate change is affecting where, when, and how much water is available. Extreme weather events such as droughts and heavy precipitation , which are expected to increase as climate changes, can impact water resources. A lack of adequate water supplies, flooding, or degraded water quality impacts civilization — now and throughout history. These challenges can affect the economy, energy production and use, human health, transportation, agriculture, national security, natural ecosystems , and recreation.

An airborne mission finds a global belt of particle formation is making clouds brighter.

EDUCATION CONNECTION

The water cycle impacts ecosystems, economies, and our daily lives. The resources in this collection help teachers guide their students beyond the classic water cycle diagram and through the complex social and environmental issues that surround water. The water cycle provides the opportunity to explore the nature of science using models and empirical evidence. 

The Water Cycle - USGS Water Science School

Versions available:

• Intermediate

Interactive Water Cycle Diagram for Kids (Intermediate)

The water cycle describes how Earth's water is not only always changing forms, between liquid (rain), solid (ice), and gas (vapor), but also moving on, above, and in the Earth. This process is always happening everywhere.

The water in the air rises up high into the sky and becomes clouds, which float away looking for a picnic to rain on. The atmosphere is the superhighway in the sky that moves water everywhere over the Earth.

Condensation

Clouds are created in the same way. Why? Condensation happens because of temperature changes. As warmer air (containing water vapor, remember?) floats up into the sky, where it is cold, condensation happens and tiny liquid water particles form ... the clouds. Colder air cannot keep the water vapor as a gas as easily as warm air.

Evaporation

As usual, you can thank the sun for making evaporation work. The sun's energy breaks the bonds that hold liquid water's molecules together and turns them into water vapor gas. Thus, it makes sense that water evaporates more easily in hot conditions, such as in the desert, rather than outside on a cloudy winter day.

Fog contains very tiny liquid water particles, like a cloud, and floats, like a cloud. Actually, fog IS a cloud, but one that swirls around your feet instead of high in the sky. Fog forms when air containing invisible water vapor encounters cooler temperatures (here, next to the ground) and the water vapor condenses out into liquid water—the cloud.

In this picture, as the day warms the air next to the ground will warm, too, and the fog particles will again evaporate back into invisible water vapor.

Groundwater flow

Yes, water below your feet is moving all the time, but, no, if you have heard there are rivers flowing below ground, that is not true.

Groundwater flow. Relate to recharge a battery.

Groundwater

When you pour a glass of water on your yard, the water sinks (infiltrates) into the ground and gets back into being a vital part of the global water cycle.

Ice and snow

Ice and glaciers are part of the water cycle, even though the water moving in them changes very slowly. The amount of ice on the Earth goes up and down as the world's climate cools and warms over thousands of years.

Lucky for us we're now in a warmer phase of the Earth's history, but the last Ice Age was only 18,000 years ago. At that time, ice covered the northern part of North America .

Ice and glaciers are still around today, as this picture shows. In fact, most of the world's freshwater, about 68 percent, is locked up in ice, snow, and glaciers.

The oceans are, by far, the largest reservoir of water on earth—over 96% of all of Earth's water exists in the oceans.

Oceans are important to the water cycle because almost all the water that evaporates from liquid to water vapor (which forms clouds) comes from the oceans.

Plant uptake

Plants depend on water in the ground for their needs. Even when you sprinkle your garden with water to give it a drink, the plants want the water that soaks into the ground next to them, not from the water that lands on their leaves. Roots in the ground pull the water up into the plant to keep it healthy.

Precipitation

The amount of precipitation that falls is different all around the world. In deserts, such as in Chile, it may only rain one inch per year, while on some mountains in Hawaii and in India, it can rain more than 600 inches per year. That is almost 2 inches every day!

Precipitation is the "exit ramp" back to earth from the water-cycle superhighway in the sky that is moving clouds all around the globe.

Of course, plants, animals, and people interact with rivers, as all kinds of life seems to thrive around rivers. If you look at a map of the world, you see how people naturally build their cities next to rivers .

And, as this satellite picture of the Nile River in Egypt, you can often pick out the rivers because of the green growth growing along them.

Even though some rainfall soaks into the ground, most of it flows over the land surface, going downhill. This runoff water reaches creeks, rivers, lakes, and the oceans, keeping the water cycle going.

With the water cycle, seepage occurs when precipitation falls on the landscape and starts to soak into the ground. The "Why?" this happens is simply gravity. But, seepage doesn't just happen downward! Water seeps upwards and sideways, too, from the ground into the bottom of rivers, lakes, and the oceans. Some of the water you see flowing in a river has come up from the ground.

Just like the flowers waiting for springtime to bloom, this snow is waiting for warmer temperatures so it can melt and get back into the ever-moving water cycle. If a lot of snowmelt happens in the spring, watch out downstream, because flooding can occur from the melting of months of accumulated snow.

The sun's heat allows liquid water to evaporate into water vapor, which in the main way water gets from the land surface back into the sky.

The sun also participates in moving water around the Earth by being the reason winds exist. The winds move clouds and the weather all over the place; all of this mixing up and moving is an important part of the water cycle.

Evapotranspiration (Evaporation and transpiration)

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The Natural Water Cycle (PDF)

Detailed Description

The Water Cycle

Earth's water is always in motion, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.

• The Water Cycle  - Description of the water cycle
• The Natural Water Cycle  - The Natural Water Cycle diagram in JPG format
• Water Cycle Diagrams - A comprehensive list of water cycle diagrams offered by the USGS Water Science School

Earth Science Week Classroom Activities

Water: a never-ending story, activity source:.

Live From Earth And Mars

Approximate time frame: 2 weeks.

Water on earth is used over and over. The water cycle, the continuous movement of water from ocean to air and land then back to the ocean in a cyclic pattern, is a central concept in meteorology. In the water cycle, the sun heats the Earth’s surface water, causing that surface water to evaporate (gas). This water vapor then rises into the earth’s atmosphere where it cools and condenses into liquid droplets. These droplets combine and grow until they become too heavy and fall to the earth as precipitation (liquid if rain, solid if snow).

Water is temporarily stored in lakes, glaciers, underground, or living organisms.

The water can move from these places by streams and rivers, returns to the oceans, is used by plants or animals or is evaporated directly back into the atmosphere.

Module Goals

Students will:

• Understand that water on earth moves in a continuous cycle.
• Be able to name and explain the stages of the water cycle.
• Be able to use Internet data to access information about the water cycle on the Olympic Peninsula of Washington State.

Overview of the Module

In this module, students will first carry out a number of activities that demonstrate the concepts of evaporation, condensation, precipitation, and soil moisture and runoff. The students will then construct a terrarium as a way to observe the water cycle as a whole. Immediately following this, students will use the Internet to acquire Real Time Data from the Olympic Peninsula which they can then use to describe how the phases of the water cycle look on the Olympic Peninsula.

Introducing the Module

To begin the module teach your students the “WATER CYCLE BOOGIE.” This is a song that teaches the terminology of the water cycle with hand movements.

“THE WATER CYCLE BOOGIE”

Evaporation, Condensation, Precipitation, Saturation. And the water cycle boogie goes ‘round and round, And the water cycle boogie goes up and down. REPEAT twice [or your choice]

After teaching the song, have a class discussion to explore students prior knowledge of the water cycle. Use the following questions to determine what concepts the students understand and to identify misconceptions.

The objective of these introductory activities is to build interest in the water cycle. This activity will allow the students to use their prior knowledge about the water cycle and to spark their interest so that they want to learn more.

Discussion questions

• Does the earth have more or less water now than 1,000 years ago? Explain.
• From where does water that is on the ground come?
• How does water get into the oceans?
• What are clouds?
• What are clouds made of?
• How does rain form?
• What do you think all those words we used when we sang the “Water Cycle Boogie” mean?

After discussing these questions with your students, explain to them that they are going to carry our several activities that will help them to better understand the water cycle.

Activity Set Up

These activities should be conducted in cooperative groups of 2-3 students. This will allow the students to have personal involvement in the activities and help them construct their own understanding of what is happening. This will require materials and set-up for each group. If small group works are not possible the activities might also be set up as centers. Groups of students could then rotate through each station. This approach would require fewer materials and less set up. A final option would be to conduct the activities as a teacher directed demonstration with the whole class observing. This would require fewer materials and less set up, however, it is recommended only if the two options discussed above are not possible.

Teacher Preparation of Activities

Students will begin the activities after the introduction to the lesson which asks them to think about if the water they drink is the same water dinosaurs drank. Each activity should begin with some opening questions, which should be discussed with the whole class, and conclude with a set of questions that students will answer in writing.

Evaporation Activity

Materials (for groups of 2-3 students).

• small dishes or jar lids (2 per group)
• tablespoons (1 per group)
• light source (sun or lamp/light) (1 per group)
• plastic wrap and or lids to cover dishes

a. Prior to the activity

Where does the water go after it forms puddles on the pavement? Where does the water go from the clothes you put in the dryer? Ask students to predict what will happen to the water if it is left out overnight in an uncovered dish. Ask students what will happen if the dishes were covered.

b. After the activity

Have students, on a sheet of paper answer these questions with a partner. Which dish evaporated faster? Where did the water go? How did the water evaporate?

Explain to the students that the process of water “going” into the air is called evaporation. Have students discuss with their partner what happens to water after it evaporates. Write some other examples of evaporation.

Divide the class into pairs. Have each pair of students get two dishes. Put one tablespoon of water in each dish. Place one dish in the sunlight, or if the sun isn’t shining, place the dish under a light source. Let students decide if they want to cover their dishes or leave them uncovered. Place the other dish in the shade. Have each pair of students observe and record what happens to the water.

Condensation Activity

• A clean, clear 2 liter plastic bottle for every 3 students
• A box of wood matches for every 3 students
• A thermometer for every bottle (available at fish stores)
• An eye dropper or other container for water

a. Prior to the activities

What makes air warm? What happens to warm air? What makes air cold? What happens to cold air? What are clouds? How are clouds made? What 3 things are necessary to form clouds? What is fog?

b. After the activities

Have students answer this question in writing: In your own words explain what we did in these two activities. What do you know about the relationship between air temperature, air pressure, condensation, and the formation of clouds?

It is recommended that these activities be carried out over two class sessions. The first session is part 1 and second session is part 2.

Session 1: Temperature changes in a closed soda bottle Tell students that they will work in groups of 3.

Each group will have:

• 1 clear plastic bottle with cap
• 1 temperature strip
• 1 strip of tape
• 1 Box of Matches
• 1 paper on which to record their data

The first step :

Tape the temperature strip into the bottle so that you can read it. Then screw the bottle cap on tightly. Lay the bottle on its side so you can easily read the temperature strip.

Read and record the temperature of the air inside the bottle. Then use both hands to squeeze the bottle as hard as you can. After about 1 minute read the strip. Then stop squeezing and read the temperature strip after about 1 minute.

What happened the temperature when you squeezed the bottle? What happened to the temperature when you stopped squeezing the bottle?

Session 2: Making a cloud-in-a-bottle

Open the bottle and pour in a few drops of water. Screw the bottle cap on tightly. Swirl the water around the inside of the bottle so that most of the inside of the bottle is wet. Squeeze the bottle and observe the temperature again. What happened?

Lay the bottle on it’s side, open the bottle, and push down to flatten the bottle to about 1/2 it’s normal size. Have someone light a match, blow it out, and put the match into the bottle while it is still smoldering. Quickly release the sides of the bottle and put the cap on tightly. Now squeeze the bottle as before very tightly for about 1 minute. Quickly let it pop open.

What happens? Hopefully, you should be able to see a cloud. In this experiment you saw water molecules condense into a cloud in the bottle. When you squeezed the bottle the air pressure in the bottle increased which raised the temperature. The warmer air caused the water in the bottle to evaporate (it became water vapor) and you could not see it. When you let the bottle pop out the air pressure in the bottle was lowered and so was the temperature. This caused the water molecules to condense into a cloud

Precipitation Activity

• A heat source to boil water
• A pot in which to boil water
• A Pyrex or other container with a handle
• A pie pan or other container

What is rain? How does rain happen? What is snow? How does snow happen? What is hail?

b. Ask students immediately before activity:

What do you think will happen to the bowl of ice, to the steam, to the bottom of the bowl?

Tell the students they need to focus on these questions during the activity.

What do you see happening on the bottom of the bowl? What do you see happening in the pie tin? How does the water get on the bowl? Are the water drops on the side of the bowl the same size? Why? Which drops are falling from the bowl? Why? Which drops look like rain? Which drops look like a cloud? How are the big drops formed?

c. After the activity:

On a sheet of paper answer these questions with a partner:

What did you see happening on the bottom of the bowl? What do you see happening in the pie tin? How did the water get on the bowl? Were the water drops on the side of the bowl the same size? Why? Which drops were falling from the bowl? Why? Which drops looked like rain? Which drops looked like a cloud? How were the big drops formed?

Explain that the small misty drops which have condensed onto the side of the bowl of ice represent a cloud. The winds in a cloud blow the small drops around so that they collide with one another. During these collisions, some drops will combine with others making bigger and bigger drops. When the drops become so large that the upward motion of the air cannot keep them in the sky, the drops fall as precipitation. If the temperature is cold enough the drops will freeze as crystals, making snow. If the drops get together first and then freeze the precipitation will be hail.

Set up this activity where students can gather around you and see what happens to the pot with ice in it and to the moisture that drips from the pot into the pie tin. Place a pot of water on the heat source until it comes to a boil. Fill the Pyrex pot with ice. Once the water is boiling, hold the bowl of ice over the steam. Place the pie tin so that the water which drips from the bottom of the bowl will collect in the tin. Continue to hold the pot of ice over the boiling water until all the students have had a clear view of what is happening on the surface of the pot with the ice.

Where does the water go when it hits the Earth?

Paper and a writing tool

What kinds of precipitation are there? What happens to precipitation when it reaches the ground? How can water be stored?

Make a list of all the places that water goes once it reaches the ground. Divide students into groups and have them make sketches or drawings as well as written descriptions of what happens to the water when it lands in these places. Have a class sharing and discussion about the answers generated.

Soil Moisture and Runoff

Materials for every 2 students.

• About 100 ml (half cup) of each of a variety of soils
• Filter paper disks folded into cones, one for each soil type
• A graduated cylinder (or a teaspoon)
• A jar of water
• A tray or other container which will catch water

From where does ground water come? What causes streams and rivers? Do different types of soil hold different quantities of water? Explain that the funnel is used to ‘channel’ the water once the soil has absorbed all it can hold.

On a sheet of paper answer these questions with a partner. How did you know the soil was saturated? What happened to the water once the soil was saturated? Where does water go after it runs to a stream? (List at least 2 possibilities.)

Every 2 students will put a cone of filter paper in a funnel. Place 100 ml (about 1/2 cup) of dry soil in the funnel and tamp the soil gently. Pour 5 ml (about one teaspoon) of water onto the soil every 30 seconds until water appears at the bottom of the funnel. Repeat the experiment with the other soils and a new filter cone. Have students describe what process happens between the water and land to form streams.

The Whole Water Cycle

Materials for terrarium activity.

• Potting soil
• A package of seeds e.g. marigold or pea
• Container for pouring water
• A plastic container e.g. small like you can get at the grocery for salad.

(Check with your local water department they may have the materials for a terrarium they will give you.)

a. Prior to building the terrarium

How do all of the parts of the water cycle fit together? What would happen if one part was left out?

b. After building the terrarium

Observe what happens to the water in this closed container and help the students observe and describe the different parts of the water cycle they see in the terrarium. Keep track of your observations in a science journal. Each day look for the following things:

What is the seed doing? On which parts of the terrarium do you see water? What new is happening in your terrarium today?

Review the water cycle boogie and then have the students do it. Explain that each student will get to build or have their own terrarium to observe the water cycle. Provide each student with a small plastic container which can be covered tightly with either a clear lid or plastic wrap. Have each student put soil in the bottom, put a plant seed in the soil, and lightly water the soil. Cover the terrarium with the lid or plastic wrap and place in a location where it can get sunshine.

The Water Cycle on the Olympic Peninsula

After conducting the activities which introduce them to the phases of the water cycle, students will now apply what they have learned by looking at data from the Olympic Peninsula to see how the water cycle occurs there.

1. Students will be directed to view a NOAA/USGS precipitation map for Washington state.

Which areas get the greatest amount of rain? How much? Which areas get the least amount of rain? How much? Why is there such a difference?

2. Students will then be directed to a precipitation map of a relatively dry area of the Olympic Peninsula. The area is near a town called Sequim, which is pronounced “skwim.” Students will investigate present and monthly rainfall and calculate the likelihood of rain using archived data .

3. Students will collect information on Forks, a town on the West coast of the Olympic Peninsula here . They will be asked if they think it is raining in the Forks area right now. Students will compare the differences in precipitation between Forks and Sequim.

4. Students will then be directed to study a relief map showing the topography of the Olympic Peninsula. [Find here]( https://data.fs.usda.gov/geodata/rastergateway/states- regions/states.php).

Study the relationship between the rainfall at Forks, stream flow data, and the level of Lake Quinalt. Students will be directed to go to the Web site for the Olympic Rain Forest to get information on Lake Quinalt and stream flow information for the Olympic Peninsula.

Students can be assigned to collect and record data from the Internet sites and make assumptions about what the data means in terms of the particular part of the water cycle.

Assessment will be carried out throughout the lesson in the form of discussions and the written responses to the various activities. The final assessment will be to have each student answer the following question: WHERE DOES WATER COME FROM AND WHERE DOES IT GO? Students should be allowed to answer this question in a final project that would be chosen from the following:

Draw or paint the answer to the question. Write a poem to answer the question. Write a life history of a raindrop. Present a play that answers the question. Use Super Paint or Kid Pix to graphically answer the question.