The lightest of the known elements. The movement of water from the atmosphere to the earth and its return to the atmosphere through condensation, precipitation, evaporation, and transpiration. A substance that flows freely. The molecules move freely among themselves but do not tend to separate like those of gases. An instrument used for measuring quantity, such as the amount or rate of flow of liquids, gases, or electric current.
Rocks are compounds of minerals.
The smallest physical unit of an element or compound, consisting of one or more atoms. Combines chemically with two hydrogen atoms to form water. O part per million One part for every one million parts. The oozing or soaking of water through the soil. The amount of force acting on a surface.