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http://en.wikipedia.org/wiki/Main_Page BY: Charlie Cowdery Precipitation is when rain falls from the clouds. Runoff can come from many things it can come from mountains, glashiers, lakes, rivers, and rain. In physics, chemistry and materials science, percolation concerns the movement and filtering of fluids through porous materials. Examples include the movement of solvents through filter paper (chromatography) and the movement of petroleum through fractured rock. Electrical analogs include the flow of electricity through random resistor networks. During the last three decades, percolation theory, an extensive mathematical model of percolation, has brought new understanding and techniques to a broad range of topics in physics, materials science as well as geography. www.floridasprings.org On average, the molecules in a glass of water do not have enough heat energy to escape from the liquid, or else the liquid would turn into vapor quickly (see boil). When the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with enough energy to escape. Liquids that do not evaporate visibly at a given temperature in a given gas (e.g. cooking oil at room temperature) have molecules that do not tend to transfer energy to each other in a pattern sufficient to frequently give a molecule the heat energy necessary to turn into vapor. However, these liquids are evaporating, it's just that the process is much slower and thus significantly less visible. Evaporation is an essential part of the water cycle. Solar energy drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. In hydrology, evaporation and transpiration (which involves evaporation within plant stomata) are collectively termed evapotranspiration. Evaporation is caused when water is exposed to air and the liquid molecules turn into water vapor which rises up and forms clouds. Evaporation is the process by which a liquid becomes a gas. It usually occurs at the surface of a liquid, When water heats up it turns into vapor wich goes into the sky and forms into a cloud. www.kidsgeo.com www.sanbrunowater.ca.gov Transpiration is the evaporation of water from the aerial parts of plants, especially leaves but also stems, flowers and roots. Leaf surfaces are dotted with openings called stoma that are bordered by guard cells. Collectively, the structures are called stomata.[1] Leaf transpiration occurs through stomata, and can be as a necessary "cost" associated with many processes such as the opening of the pistil and allowing the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration also cools plants and enables mass flow of mineral nutrients and water from roots to shoots. Mass flow is caused by the decrease in hydrostatic (water) pressure in the upper parts of the plants due to the diffusion of water out of stomata into thetranspiration is directly related to the degree of stomatal atmosphere. Water is absorbed at the roots by osmosis, and any dissolved mineral nutrients travel with it through the xylem. The rate of opening, and to the evaporative demand of the atmosphere surrounding the leaf. The amount of water lost by a plant depends on its size, along with the surrounding light intensity, temperature, humidity, and wind speed (all of which influence evaporative demand). Soil water supply and soil temperature can influence stomatal opening, and thus transpiration rate. A fully grown tree may lose several hundred gallons (a few cubic meters) of water through its leaves on a hot, dry day. About 90% of the water that enters a plant's roots is used for this process. The transpiration ratio is the ratio of the mass of water transpired to the mass of dry matter produced; the transpiration ratio of crops tends to fall between 200 and 1000 (i.e., crop plants transpire 200 to 1000 kg of water for every kg of dry matter produced).[2] Transpiration rate of plants can be measured by a number of techniques, including potometers, lysimeters, porometers, and heat balance sap flow gauges. Desert plants and conifers have specially adapted structures, such as thick cuticles, reduced leaf areas, sunken stomata and hairs to reduce transpiration and conserve water. Many cacti conduct photosynthesis in succulent stems, rather than leaves, so the surface area of the shoot is very low. Many desert plants have a special type of photosynthesis, termed Crassulacean acid metabolism or CAM photosynthesis in which the stomata are closed during the day and open at night when transpiration will be lower. Condensation is the change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase.[1] When the transition happens from the gaseous phase into the solid phase directly, bypassing the liquid phase the change is called deposition, which is the opposite of sublimation. Condensation commonly occurs when a vapor is cooled to its dew point, but the dewpoint can also be reached through compression. The condensed vapor is called a condensate, the laboratory or the industrial equipment used for condensation is called a condenser. The science of studying the thermodynamic properties of moist air and the interrelationships between these in order to analyze, and predict properties by changing in the conditions of moist air is called psychrometry. The interrelationship can be graphically represented, and prediction carried out graphically by the psychrometric chart Most people think the water is condensation, but condensation is only the process of change. Water vapor that naturally condenses on cold surfaces into liquid water is called dew. Water vapor will only condense onto another surface when the temperature of that surface is cooler than the temperature of the water vapor. The water molecule brings a parcel of heat with it. In order to have condensed, the molecule tranfers its kinetic energy to the atmosphere. When water vapor condenses into liquid water, the hydrogen bonds form again and release latent heat, which increases the sensible heat and causes the air temperature to rise. Sensible heat is removed from the air and the temperature drops when evaporation is occurring and latent heat is converted to sensible heat and the temperature rises when condensation occurs. When vapor is cooled it it goes down to the ground as due. cd7.e2bn.net http://www.sanbrunowater.ca.gov www.kidsgeo.com www.floridasprings.org http://en.wikipedia.org/wiki/Main_Page