GEF

Unit 2  |  Water Science and the Water Cycle 44 The property of water as a universal solvent can also have negative consequences for the environment. For instance, toxic chemicals from industry, farming, and other human activity are readily dissolved and carried by water into streams, lakes, and groundwater . These dissolved chemicals can enter sensitive ecosystems such as wetlands and can be difficult to eliminate. Other physical properties make water a unique substance. Water is the only type of matter on Earth that is found in three states— solid , liquid , and gas . It takes a large amount of energy to force apart the strong hydrogen bonds between water mol- ecules. This property means that it requires a lot of energy, expressed as latent heat , to change water from a solid to a liquid or from a liquid to a gas. Compared to most other liq- uids, water has a high boiling point and a low freezing point. Therefore, water is found in liquid form across most of the Earth. Glaciers are an example of water in its frozen state floating in water in its liquid state. GROUNDWATER Any form of fresh water supply, such as aquifers, located underground, often supplying wells, springs, and agricultural irrigation. WETLANDS Land areas that are per- manently or seasonally saturated with water. SOLID One of four main states of matter in which the mol- ecules vibrate about fixed positions and cannot migrate to other positions in the substance. LIQUID One of four main states of matter in which atoms or molecules can move freely while remaining in contact with one another. GAS One of four main states of matter composed of mol- ecules in constant random motion. LATENT HEAT The heat absorbed by a material that causes a change of state without an increase in temperature.

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