Water on Earth
Map
Arrows point from what you learn first to what it opens. Point at a concept to light up its chain and where it comes back deeper. Right-click a concept (or press and hold it) for its lessons and stories.
- Proven to depth123
- Open
- Locked
- Comes back deeper
Learning path
In the order the concepts build on each other.
- Clean drinking waterLockedWater from rivers and wells can carry mud and germs too small to see. At a water treatment plant the mud is left to settle, the water is filtered through sand, and a little chlorine is added to kill the germs, so the water from our taps is safe to drink.Opens after: Separating mixtures
- Fresh and salt waterReadyAlmost all the water on Earth is salty sea water, which we can't drink. Only a very small part is fresh water, and most of that is frozen in ice or hidden underground. So the fresh water we can use is precious, and we shouldn't waste it.
- The water cycleLockedWater goes round and round. The Sun warms seas, lakes and puddles, and some of their water evaporates into the air. High up, the air is cold, so the water condenses into the tiny drops that make clouds. The drops fall as rain or snow, and the water runs back to the sea or soaks into the ground, ready to go round again.Opens after: Evaporation and condensation
- GroundwaterLockedSome rain and melted snow soaks down through the soil until it reaches rock it can't pass, and collects there: that is groundwater. People reach it by digging wells, and in Iran also by qanats, long sloping tunnels that bring groundwater out with no pump. If we take out more than the rain puts back, wells run dry, and dirt that gets into the ground can spoil the water.Opens after: Soil, The water cycle
- Saving waterLockedFresh water is scarce, and the water in our taps has come a long way to be cleaned for us. Small habits keep it from being wasted: turning the tap off while brushing, getting a dripping tap fixed, short showers, and watering plants in the cool of morning or evening.Opens after: Fresh and salt water
- QanatLockedA qanat is an underground tunnel that brings groundwater to the surface without a pump. It starts at a deep mother well at the foot of the mountains, where there is plenty of groundwater, and runs with a gentle downward slope to a village, where the water comes out. A line of wells from the surface to the tunnel let the diggers lift out the earth and let air in. People in Iran have dug qanats for thousands of years.Opens after: Groundwater
Connections to other domains
- Clean drinking water needs Separating mixturesMatter and Its Properties
- Groundwater needs SoilRocks and Soil
- The water cycle needs Evaporation and condensationMatter and Its Properties