Water cycle phase changes

To move water at the surface of the Earth, the water cycle uses phase changes. A phase change occurs when matter changes its form, or state. This includes instances when a substance changes from liquid to gas (or gas to liquid), liquid to solid (or solid to liquid), or solid to gas (or gas to solid). 

Arguably, there is nowhere on Earth where phase changes are more natural and more important than in Earths water cycle. These processes keep the balance of water fairly constant in our oceans,... 

Earths water cycle does not start or stop in any one place. The water cycles many steps are constantly changing the phase of water. This process keeps water moving around the globe. The role of each phase change in the water cycle is described in this chapter. Exactly... 

Snow sublimation happens particularly often in the western United States, where warm, dry winds often blow after an intense cold spell. When these warm, dry winds blow over an area covered in snow, the snow sublimates directly to a gas, skipping the liquid phase entirely. In some areas, this wind is known as the Chinook Wind (Chinook is a Native American word that means snow eater. 8) Although sublimation plays a less vital role in the planets water cycle than some other phase changes, such as evaporation and condensation, it still serves to move water around Earth. 

Like sublimation, deposition plays a lesser role in the water cycle than some other phase changes, but it is no less important to the overall process. Deposition moves gaseous water in the air into the planets water cycle. 

You ve likely seen or heard about many of the phase changes that happen regularly as part of Earths water cycle. But why do they happen How do they happen Ultimately, the answers lie in how molecules behave inside matter. This behavior determines if a substance takes the solid, liquid, or gaseous form, and when it changes from one state to another. 

Phase changes happen all around us all the time, not only during super-large scale events, as in Earth s water cycle. Take a tour of your home and you will likely find phase changes at work in nearly every room. 

The water cycle is the continuous circulation of water within the Earth s hydrosphere. As water moves through the cycle, it changes state between liquid, solid, and gas phases. 

Lyophilization (or freeze-drying) is a process utilized to convert a water-soluble material filled into a container to a solid state by removal of the liquid while frozen. The process requires the use of deep vacuums and careful control of temperatures. By conducting the process under reduced pressure, the water in the container converts from ice directly to vapor as heat is applied and is removed from the container by the vacuum. The dissolved solids in the formulation cannot undergo this phase change and remain in the container. At the completion of the cycle, the container will be returned to near atmospheric pressure stoppers are applied or fully seated and crimped as described above. Lyophilization is particularly common with biological materials whose stability in aqueous solution may be relatively poor. The time period in solution and the temperature of the solution are kept at a specified low temperature to prevent product degradation [35],... 

The saturation vapor pressures of HDO and H2 0 are lower than those of H2 0, both over liquid and solid phases. These differences play an important role in the course of the atmospheric water cycle as they cause fractionation effects at vapor/liquid and vapor/solid phase changes, with the condensed phase in equilibrium with vapor being enriched in heavy isotopes. The fractionation coefficient a is defined as the ratio of D/H or in the condensed phase to the value of... 

SECTION 18.3 Earth s water is largely in the oceans and seas only a small fiaction is freshwater. Seawater contains about 3.5% by mass of dissolved salts and is described as having a salinity (grams of dry salts per 1 kg seawater) of 35. Seawater s density and salinity rary with depth. Because most of the world s water is in the oceans, humans may eventually need to recover freshwater from seawater. The global vrater cycle involves continuous phase changes of water. 

The functioning of these sprinklers can be initiated by an electronic detection system, or by heat-sensitive valves at each sprinkler head. When a fire is detected, a spray (or more recently, a mist) of water is emitted. The water absorbs the heat of the fire through a phase change to steam and thus arrests the combustion cycle. In certain appHcations where oil fires are expected, such as in restaurant kitchens, a special foam or gel replaces the water in the system. 

All the water on Earth is connected in a global water cycle ( Figure 18.15). Most of the processes depicted here rely on the phase changes of water. For instance, warmed by the Sun, liquid water in the oceans evaporates into the atmosphere as water vapor and condenses into liquid water droplets that we see as clouds. Water droplets in the clouds can crystallize to ice, which can precipitate as hail or snow. Once on the ground, the hail or snow melts to liquid water, which soaks into the ground. If conditions are right, it is also possible for ice on the ground to sublime to water vapor in the atmosphere. 

Figure 2. Removal of cyanogen c glycosides of flaxseed due to two-phase solvent extraction with methanol-am-monia-water/hexane (95 10 5, v/w/v) (A) change in water content, (B) change in contact time and meal-to-solvent ratio and (C) change in the number of extraction cycles.

These apparently opposed forces of gathering and scattering cause all the change in the world. Every liquid river is a mass of gathered atoms that can flow and scatter. Water can dissolve mountains and can evaporate into the air. It is the most prevalent representative on Earth of the liquid phase. As such, water is necessary for protracted cycles of change on Earth. 

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