A clear liquid with no color, taste, or smell in its pure form.
Water is a compound of hydrogen. It is scientifically known as H2O; two hydrogen atoms attached to every oxygen atom. Water is a very important natural resource that is found everywhere on the earth. It fills our lakes, our rivers, and our oceans. It exists in our atmosphere. It soaks beneath the soil and collects just below the surface. It is in the food we eat, the plants that grow, and the animals that live and breathe in all parts of the earth. Without it there could be no life on Earth. In fact, nearly three-quarters of our planet is covered by water.
Properties of Water
Water has some amazing properties that make it very unique. Water is the only substance on Earth that can exist naturally in all three "states" — a liquid, a solid, and a gas. As a solid, it is ice. We all know the liquid form because we drink it, bathe in it, swim in it, and pour it. When water is heated up to just the right temperature it turns into a vapor — like the steam rising off of your cup of hot chocolate. Learn more about states of water here. You might also want to visit Science Trek's States of Matter site.
Besides being the only substance on earth that can perform these feats, water has some other tricks many do not know about. Take a look at these facts:
- Water boils at 212° F (100° C) and freezes at 32° F (0° C) at sea level. These temperatures decrease, the higher above sea level you go.
- When water freezes, it freezes from the top down and the ice floats on the surface of liquid water. If it did not, fish would not survive the winter in a river or a lake.
- Water is one of the few substances that expands when it freezes.
- Water dissolves more minerals, vitamins, and chemicals than any other liquid. For this reason, it is called the “universal solvent.”
- Water has a natural ability to be attracted to itself and so it collects in beads. This causes it to form drops rather than spread out over a surface.
- Water has a property called surface tension. Because of surface tension, some insects can actually sit on the top of the water.
- Pure water has no smell or taste and cannot conduct electricity. Dissolved minerals in water give it taste, smell, and the ability to conduct electricity.
The Water Cycle
The earth has a limited amount of water. We have the same amount of water on earth today as we did millions of years ago. We keep using the same water over and over again. Water keeps recycling around and around in a closed system called the water cycle. It does this by changing its state.
When the sun heats water in the oceans, lakes, or rivers some of the water turns into water vapor in the air. The water vapor forms into clouds as it cools. This is known as condensation. When the drops of water get big enough in the clouds they become too heavy and fall back to the earth as precipitation, otherwise known as rain, hail, sleet, or snow.
The water that falls to the ground as precipitation runs off into lakes and rivers and is known as surface water or it can soak into the ground to become groundwater. Over time, the surface water and the groundwater can travel back to the oceans which completes the water cycle and starts the process all over again. Read more about the water cycle here.
Sometimes we take water for granted because it seems like there is a never-ending supply. After all, if you look at a picture of Earth from space it is one big blue ball! What we see is the surface water that exists in lakes, rivers, ponds, streams, glaciers, polar ice caps, snow, mud puddles, and oceans.
The oceans contain 97% of the Earth's water. But the ocean's salt water, as it is called, is not consumable by most land plants and animals. The dissolved salts make it undrinkable and even harmful for plants and animals.
Freshwater constitutes the remaining 3% of the earth's water. Most of this freshwater is frozen in glaciers and icebergs. So the liquid freshwater must provide for the rest of the planet. That isn't very much when you consider the number of people, plants, and animals that must share this freshwater.
Surface water is easily polluted or contaminated. Mud, animal waste, parasites, chemicals, garbage, and other foreign matter can make the water unusable. This contamination of surface water contributes to many deaths over the globe where clean water is not available. In areas where communities have the power to clean their water before use, this danger has been avoided. Read more about surface water here. Here's more about oceans, and more about freshwater.
Groundwater is water beneath the earth's surface. It filters down between the layers of rock and soil and ends up in underground collection places known as aquifers.
Most of the water we use in Idaho comes from groundwater. Wells are dug to get groundwater from aquifers. The water is pumped out to be used on farms, in industry, for city water supplies, and other uses. Ground water is often safer to use than surface water. The layers of soil and rock that the water must trickle through to get to the aquifer actually cleans and filters pollutants from the water. Read more about groundwater here.
The water over a given geographic area tends to drain from the mountains to the lowest point; usually a river or a lake. This includes all streams, rivers, ponds, lakes, and groundwater that drain into the same general area. This geographic area of water drainage is known as a watershed. It can be quite large but does not necessarily need to be. Learn more about watersheds — even find a map of the watershed you live in by your zip code here.
How do we use water?
Water isn't just for drinking, it is also used for growing crops, cooking, cleaning, and transportation. Water is used for cooling, for running equipment, or for moving heavy loads. We also use water to generate power, to fight fires, for sanitation, in manufacturing, in mining, and much more.
Water is used for recreation ‐ for boating, waterskiing, and swimming. In its frozen form, it offers additional recreational opportunities such as ice skating, hockey, skiing, and snowboarding.
Water Became a Tool
Water is so important to life on the earth. Humans found ways early in history to manage and use water as a tool.
One of the first needs was to get water from one place to another for drinking and for growing crops. Civilizations started near water sources. Carrying water in jugs or containers was the first method of transporting water home. But as the size of civilizations expanded, new ways needed to be developed to get water from one place to another in larger quantities and over greater distances. Over time, canals, aqueducts, tunnels, wells, pumps, and water storage systems were created.
Early in history water was used as a tool to drive waterwheels for grinding and sawing. Water was also used as transportation for rafts and canoes. In the logging industry, trees that had been cut floated down rivers to get them to wherever they were needed for building or for other uses. Over time, boats, ships, submarines, and aircraft carriers have been added to the long list of water-friendly transportation.
Since water has long been used for cleaning ‐ water has been a means for getting rid of substances that were waste. Washing clothing, bathing, preparing food, personal hygiene, and toileting were at one time in history all done in the local river. This may sound disgusting to people living in the modern 21st century, but even the animals used the river for similar purposes. Drinking water from the local lake, pond, or river was done without regard to how truly clean it might be.
Water treatment programs now exist in most major population areas to treat water that has been used for waste processes before returning it to the drinking water supply. Water treatment protects consumers from parasites and bacterial and chemical contamination. Learn more about the history of drinking water treatment here.
Conservation of water is something that everyone can do. We only have so much water on this earth and so learning to use it wisely is important to us all. If we damage it to the point that there isn't any left or what is left is no longer usable ‐ then we are all in trouble. Conservation of water is about learning to use it wisely and carefully. We can start by not wasting water. Don't leave the water running when you brush your teeth, take showers instead of baths, fix leaky faucets, and keep drinking water in the refrigerator rather than running the faucet to get the water cold. Do your part to help conserve water so there is enough to go around for years to come!
Dams and Hydropower
Dams are another way that water is managed. Dams can collect water for future use and control the flow of water to prevent floods. Dams are constructed in an existing river to slow the flow of the water. This creates a man-made lake known as a reservoir.
Power can also be created using dams. This method of power generation is known as hydroelectric power or hydropower. Hydropower is energy that is generated from the flow of water using huge power generators placed inside dams. The water flowing through the dams spins giant turbine blades which are connected to generators. The power produced is sent to homes and businesses in the form of electricity. To learn more about Hydropower visit the Foundation for Water and Energy Education here.
Geysers are an amazing site to see. A plume of water that sprays from the ground ‐ sometimes at regular intervals ‐ is known as a geyser. But what causes a geyser? Groundwater in some parts of the world comes in contact with rocks that have been heated by the forces of volcanic activity. The heated water must reach a boiling temperature in order for a geyser to occur. But if it indeed does reach these extreme temperatures, steam forces the water out of the ground like a pot boiling over. Sometimes there is enough pressure built up to spray the water and steam great distances into the air.
Just as we can't live without water, the opposite can also occur. Too much water at just the wrong time and in just the wrong place can be equally dangerous. Floods, tsunamis, hurricanes, and even drinking too much water can be harmful.
- Floods generally happen when rivers fill up too quickly for their sides to hold. Severe rainstorms or fast spring thaws can cause the water to spill over the sides of a river and flow out onto the surrounding land; sometimes too quickly for anyone to escape. Floods were at one time a way to fertilize the land near the river, but as more and more people built near the river, this became more dangerous to people and their possessions.
- Tsunamis are ocean waves that move quickly toward shore after an earthquake. The size of a tsunami depends on the strength of the earthquake, the features of the ocean floor, and other factors. Tsunamis can flow inland for many miles and wash away buildings, trees, animals, and threaten communities.
- Hurricanes are enormous storms that form out over the ocean. They swirl in a circular pattern. If they move inland, they can bring great amounts of rain and wind. The wind can blow waves from the ocean into places that are inhabited. The rain and wind can destroy buildings, and trees, and endanger other life.
- We have all been told to drink plenty of water. Our bodies are made of about 60% water. Drinking water helps regulate our temperature, move waste products out, aid digestion, lubricate our joints, and lots of other important jobs. Not drinking enough water can lead to dehydration which can be dangerous. But can you drink too much water? The answer is yes — although it rarely happens. The kidneys process all of the water we drink and move it to our urinary system where we get rid of it. Along with the water, we also get rid of extra minerals, salts, dead germs and bacteria, and any other unneeded extras that our body wants to clean out. If we drink too much water, this causes the kidneys to work harder than is necessary. So how much is too much? Drink until you are no longer thirsty — but not sloshy. That rule should make getting enough water easy. Drink extra after exercise and when it is hot. Remember, all your liquids count towards this daily supply, because they all contain water.
How Much Do You Know?
Check out these challenge questions, quizzes, and surveys from the U.S. Geological Survey to see if you know the answers to intriguing questions about water, such as "Are raindrops tear-shaped?", and "How much water does it take to grow a hamburger?" Good luck!!
Top 10 Questions
Thanks to Dr. Jan Boll, professor of biological and agricultural engineering, University of Idaho; and Dr. Sarah Godsey, assistant professor, department of geosciences, Idaho State University for the answers.
What is water made out of?
Water is made out of oxygen and hydrogen atoms that are put together in a really interesting way. They are put together so that they are a polar molecule. Imagine that the oxygen is your head and the hydrogen atoms are your shoulders. This way, they are a little off balance and that is really important for water because it makes a charged molecule. As a result, water has all of these unique properties that help to make life on Earth possible. (From Brianna at Basin Elementary School in Idaho City)
Where does water come from?
Water goes through a cycle called the hydrologic cycle, or water cycle. Water falls from the clouds as mostly rain or snow. Then, it hits the Earth's surface and moves to different places, eventually evaporating back up to the clouds. So, there really is no one place water comes from because it keeps cycling around and around. (From Alea at Kamiah Elementary School in Kamiah)
Why does water have no color?
It is true that water has no color if you look through a glass because light goes through it. However, if you look at deeper water systems like the ocean or a swimming pool, there is coloration to the water that comes from dissolved particles. The color we see is actually everything that does not reflect back to our eyes. So, it all depends on the kind of particles in the water as to what color we may see. (From Cameron at Dalton Elementary School in Dalton Gardens)
How is the water we drink safe?
It depends on where the water is coming from. Typically, the water coming into our homes has been treated by the city. The city has a water department and they are responsible for making sure that the water that comes through the tap is safe. Most cities have a report that you can find that tells you exactly what they have found in the water. That doesn't mean that there is nothing in the water we drink, but that if there is, it is below any level of concern for the citizens. If you have well water at home, it is important to check it and make sure it is safe to drink. When we look at water, we try to make sure it's as safe as can be from where it falls or originates. That way, we don't have to spend a lot of money cleaning up water. (From Kendall at Adams Elementary School in Boise)
Do we drink water that was on Earth millions of years ago?
You can actually calculate the likelihood that you are drinking a molecule of water that had previously been drunk by someone like Abraham Lincoln. The chance is really high because there are just so many water molecules in a particular glass of water. So, yes, we are drinking water molecules that have been cycling around and around in the hydrologic cycle for a really long time. (From Adrianna at Cynthia Mann Elementary School in Boise)
Why does my faucet water stain my sink brown?
It is pretty common that the combination of water and oxygen can allow the metal parts of our sinks to rust. The rust often creates that brown color that we see. (From Paige at Adams Elementary School in Boise)
How does water evaporate from the ground up to the sky?
Water molecules are always in motion and when water is warmer, it will have a lot of motion. Water itself is a saturated system, meaning there is no air or little air in it. If the air around water is really dry, then there are fewer molecules of water in the air. There will be a gradient between the water and the air and the water molecules on the surface of the water will jump into the vapor phase. This happens because there is energy in the system. (From Braden at Kamiah Elementary School in Kamiah)
How much of the world's water is polluted?
The majority of Earth is made up of oceans, and we don't have good testing to determine pollution of those oceans. We are mostly concerned with testing water that is fresh water or ground water. We don't have an answer for the entire world, but we can make a guess. There are waters that have chemical constituents that we are concerned with for beneficial uses. For example, the water we use to drink. Most of that water is not polluted beyond our ability to clean it. When we look at water that fish live in and other life forms, we have some concerns. In areas where there is a lot of human activity, there is concern over the pollution of water. (From Katie at Basin Elementary School in Idaho City)
Is there water under the Earth's crust?
There is water beneath the surface of the Earth. A lot of the water that was beneath the surface of the Earth is now at the surface of the Earth because it has come to the surface through volcanic eruptions. The amount of water beneath our feet can have an impact on what happens during an earthquake. If there is an area with a lot of water or a little bit of water, it can affect the shaking. If there is a volcanic eruption, the water can affect the type of eruption that occurs. (From Elijah at Dalton Elementary School in Dalton Gardens)
Is ground water always clean?
Ground water is not always clean. The deep, deep ground water is typically clean. When we drill wells, we test to make sure it's clean. The shallow ground water that is only a few feet below the surface, however, can be influenced by anything that happens on the surface. Farming, lawn care, and many other things influence the water that is near or on the surface. In order to call it polluted, it has to go above a certain concentration, so we have to be careful and understand that. (From Gavin at Adams Elementary School in Boise)