Download Group 1 Hydrologic Cycle Notes definitions terms 2

3.1 Hydrologic Cycle
-Importance of Water
-Properties of water, water as a polar molecule, the hydrologic cycle (precipitation, transpiration,
percolation, water table, leaching)
-Provide at least one hydrologic cycle diagram
(http://polaris.umuc.edu/cvu/envm/hydro/hydrologic-flash.html)
Importance of water-absorbs and releases thermal energy and moderates temperature fluctuations
How does it moderate temperature fluctuations?
water absorbs heat from the air causing the water itself to warm up, and the air to cool down. As
water in order to change forms. As more heat is absorbed water goes from liquid to a gas. As it
loses heat
Water moderate air temperature by absorbing heat from air that is warmer, and releasing the stored
heat to air that is cooler.
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Water needs to give away energy in form of heat when it goes from gas to liquid, and from liquid to solid.
The opposite is also true: water needs to take energy in form of heat when going from solid to liquid or
liquid to gas.
The latter is the reason we perspire: evaporating water cools down our skin.
Note that, in order to give away, or take heat, the water in the atmosphere needs something with a mass.
Very small droplets of water doesn't have enough mass and that's why you can see dew or frost rim on
the trees in the morning: droplets are only appearing when in contact with something solid.
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-is an excellent solvent
solvent-
-is the medium in which metabolic reactions happen
-makes up over 60% of a cells mass (for humans we are 75% water)
- supplies hydrogen atoms to producers during the metabolism of key organic molecules during
photosynthesis and oxygen atoms to all organisms during cellular respiration
-is a reactant in some metabolic activities and a product in others
Water as a polar moleculeWater molecules are held together by covalent bonds. It is H20, which is basically 1 oxygen
atom and 2 hydrogens. The definition of polar molecule is a molecule that has a positive and a
negative end. The electrons are drawn to the oxygen atom which creates a negative charge and
a positive charge near the hydrogen end of the molecule. The positive and negative balance
each other out so the molecule has a positive pole and a negative pole which is referred to as
the polar molecule. So one negative water molecule repels another water molecule but it also
attracts the positive, the attraction between the opposing charges of different molecules creates
a hydrogen bond. Hydrogen bond- the type of bond that is formed between the positive end of
one water molecule and the negative of another molecule. Then the hydrogen bonds pull the
water molecules together.
The hydrological CycleThe movement of water through the biosphere is called the hydrological cycle, also known as
the water cycle. The water that reaches the Earth’s surface comes in many ways such as rain,
snow, sleet and hail. Some of it can remain on land in lakes, oceans, and rivers or it can be
absorbed through the soil. If the rock is permeable some of the groundwater may seep through
the surface forming springs, so by absorbing energy through the sun it evaporates and becomes
water vapour. The water vapour rises upward into the atmosphere until it reaches a point where
the temperature is low enough for it to condense into tiny droplets of water. When the
temperature is right the droplets can form together and make snow.
Percolation- the downward pull of water. the movement of a liquid through a porous material
such as soil particles.
Transpiration- the loss of water through plant leaves
Precipitation - when water falls to the earth’s surface in the form of rain, snow, sleet and hail
Water table- the top level of the region below the ground that is saturated with water.
Leaching- the removal of soluble minerals by percolation.
The freshwater comes from two sources which is groundwater and surface water. Precipitation
that collects above ground is called surface water and it increases surface run off which makes
lakes and rivers. after the rainfall seeps into the soil and this happens because of gravity, which
is also called percolation (the downward pull of water). The larger the soil particles the faster the
percolation rate. The water table forms above a layer of relatively impermeable bedrock or clay.
The greater the rainfall the higher the water table will be. When the water seeps downward it
carries dissolvable organic matter and minerals into the lower layers of soil. That process is
called leaching. Leaching is the removal of chemicals from the upper layers. Removing these
chemicals is a serious problem because the plants require these nutrients for growth and
development. Plants help to correct the problem of leaching. Long branching roots extend deep
into the soil to help bring the minerals and chemicals from the lower layers of the soil back to the
surface.
Why do clouds form??
condensationThe fact that condensing water releases energy in form of heat, is the reason we see clouds growing,
sometimes all the way to a thunderstorm. In the clouds, where water condenses, the air temperature is
higher than around it and the cloud keeps rising, growing bigger.
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