Facts for Kids

Water is the clear liquid you drink, swim in, and use to wash. Chemists write its formula as \(\mathrm{H}_2\mathrm{O}\), which means each tiny water piece has two hydrogen atoms and one oxygen atom. Water is nearly colorless, has no strong smell, and usually no taste, but it acts like a helper that pulls many other substances apart — that is why it is called a solvent and why sugar or salt disappear into it when you stir lemonade or soup.

Water covers about \(71\%\) of Earth's surface and most of that is in the seas and oceans (about \(96.5\%\)). It moves around the planet by evaporating, forming clouds, falling as rain or snow, and flowing back into rivers and seas. Water is essential for every living thing, even though it does not give food energy.

Water is the special liquid that makes life possible on Earth. Long ago, the first tiny life lived in water, and today most fish live only in water because they breathe with gills. Some fish, like lungfish, also have lungs and can gulp air. Amphibians, such as frogs, spend part of their life in water as tadpoles and part on land as adults. Many small animals and insects have tubes or tiny gills to get oxygen from water.

Many ocean food chains begin with tiny plants and animals called plankton. Water’s tiny sticky pulls, called hydrogen bonds, help it store and move heat, give it surface tension so bugs can skate on ponds, and let water climb up plant stems to feed leaves. What animal do you think needs water the most?

Color and look of pure water is slightly blue when you see a lot of it, because water absorbs a little red light and lets blue light travel farther. That is why a deep lake or sea looks blue, and why adding algae or tiny bits can make water look green or brown. Water bends light more than air, so things under the surface look a bit closer than they really are.

Pure water is basically tasteless and has no smell, but natural water often has dissolved minerals or tiny plants that give it a mild taste or scent. Some animals can smell or sense water from a distance to find a drink. How a drop shines, beads, or makes ripples depends on those tiny sticky hydrogen bonds working together.

Freshwater is the water people use for drinking, cooking, washing, and growing food. About seven out of ten buckets of fresh water people use worldwide go to farms. People also fish for food, and fishing gives a noticeable share of the protein many communities eat. Cities and factories use water too, and millions of people create large amounts of wastewater each year. When that water is not cleaned, it pollutes rivers and lakes.

Safe water for drinking is called potable water and can be made safe by methods like filtration or distillation. But many people still lack safe, nearby water or live in places with too little water. If you want, try one simple habit at home to save water—what will you choose?

Water molecule means one tiny unit of water with a special shape: two hydrogens joined to one oxygen in a bent form with an angle about \(104.5^\circ\). The oxygen side pulls a little more on the electrons, so that side is a bit negative and the hydrogen sides are a bit positive. This uneven charge is called "polar," and it makes water act like many tiny magnets.

Each water molecule can stick to others with "hydrogen bonds," and those sticky links give water some important qualities. Because of them, water can dissolve many things like salt and sugar (think of stirring sugar into tea), it holds heat well so places near water change temperature slowly, and it makes drops bead up or climb thin tubes to help plants drink.

States of water means the ways water can be: solid (ice), liquid (water), and gas (steam or vapor). At normal air pressure, ice melts at \(0^\circ\)C and water boils at \(100^\circ\)C. But water can still turn to vapor below boiling — for example, puddles slowly vanish as they evaporate, and wet clothes dry in the sun. At high places like mountains, water boils at lower temperatures, so some foods cook more slowly there.

Ice on Earth usually has a six-sided, or hexagonal, crystal shape that makes snowflakes. In very cold or very squeezed places (like high in the air or deep inside planets), water can freeze into different crystal shapes. Ice is also lighter than liquid water, so it floats — this helps fish and pond life survive winter.

Water cycle is the name for how water moves around Earth. Warm sunlight makes water evaporate from oceans and lakes. Plants send water up and out as transpiration. Water vapor cools into clouds (condensation), then falls as rain or snow (precipitation), and flows back to rivers and seas (runoff). This loop keeps water moving where living things need it.

Earth sits at the right distance from the Sun so water can be liquid, solid, and gas. Gravity holds the air that keeps moisture near the surface, and gases like water vapor help keep temperature steady. Bigger planets or very different pressures can change how water behaves, so being the right size and distance from a star helps a planet support life.