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Fig
5-4: The states of water and water phase changes |
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THE
HYDROLOGIC CYCLE
- Three states of
water -- solid, liquid, gas
[F 5-4, p 140, above]
- Processes of changes of states of water
- Molecular activity; surface
tension
- Liquid water has molecules in
motion
- The warmer the water, the greater
the motion
- Some molecules take on enough
energy to break through surface tension and become water vapor, a gas, in the atmosphere
- There also are gaseous water
molecules becoming
liquid water or
water ice, at the same time, depending upon the
prevailing temperature
- Melting/freezing -- solid-liquid-solid
- "Hidden," latent heat
leaves
liquid water when it freezes into water ice and is released into the
"environment"
- Melting occurs when water ice
absorbs
enough energy to change to the liquid
state.
- Ice absorbing
just enough energy to melt will become liquid water but still at the
32° F ice point temperature
- The energy
absorbed or released is
called the latent
heat of fusion
- Evaporation/condensation: liquid-gas-liquid
- Evaporation: Liquid water transforms into
gaseous water vapor by absorbing the latent heat of vaporization
- Boiling water
- A "mud" puddle
disappears
- Condensation occurs when water vapor
releases
the latent heat of vaporization through cooling and becomes liquid water
- Mist on a bathroom mirror
- "Fog" on the inside of
automobile windows (really isn't fog)
- Some clouds in the sky
- Sublimation/Deposition/Sublimation: solid-gas-solid
- In these two processes,
the
liquid state of water is bypassed
- Sublimation occurs when water ice transforms
directly
into gaseous water vapor
- Disappearance of snow and ice from
sidewalks when the temperature remains below freezing
- Deposition occurs when gaseous water vapor changes
directly into water ice
- Formation of high altitude cirrus clouds
- Formation of low elevation clouds
in winter cold
- Formation of
snow flakes
- Frost
on surface objects (grass, automobiles, etc.)
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Fig 5-5c: Frost --
Delicate ice crystals deposited directly from water vapor |
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- Storage or release of
latent energy occurs with each change of state
- Study the energy
changes of Figure 5-6.
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Fig 5-6: Latent
heat gains and losses with changes of state of water |
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