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Water
Science 7
• Of all the water on Earth, 97% is in
the ocean and only 3% is fresh
water
–2% is frozen
–less than 1% for drinking water
The Three Forms of Water.
• Solids: When water becomes very cold
and freezes it will change from a liquid to
a solid. It has a definite form and
shape.
• Ice, frost, glacier
The Three Forms of Water.
• Liquids: When water takes the shape of
its container it is in a liquid form.
• Lake, river, rain
The Three Forms of Water.
• Gases: When water is seen in a vapor
form and has no definite size or shape it is
in a gas form. Geyser, clouds, fog
Precipitation
• the process in which
water (in the form of
rain, snow, sleet, or
hail) falls from clouds
in the sky.
Surface Runoff
• - rain, snow melt, or other water that flows
in surface streams, rivers, or canals.
• A watershed is the region of land from
which surface runoff drains into various
bodies of water.
• Recharge Zone - The area of land, and
permeable features, that allows water to
replenish an aquifer (porous, watersaturated layer of earth materials through
which water flows). This process occurs
naturally when rainfall filters down
through the soil or rock into an aquifer.
Subsurface Runoff
• - rain, snow melt, or other water that flows in
underground streams, drains, or sewers.
• Groundwater – results from precipitation that
infiltrates the ground & seeps downward
through fractures, pores & other spaces in soil
& rock. Infiltration rate depends on porosity
(percentage of void space in a rock), type,
texture & structure of the soil & moisture
content (Permeability)
• Percolation – Movement of water through the
soil by gravity & capillary forces
Subsurface Runoff
• Zone of aeration (unsaturated zone) –
layer of earth in which rock & soil may be
moist, but are not saturated with water;
full of air (vadose water)
• Water table – Line between unsaturated &
saturated zones – will vary due to rainfall
amounts, runoff & infiltration. (During wet
weather, water table is closer to surface;
during dry weather, it falls away from
surface)
• Zone of saturation – layer of soil above
bedrock that is completely filled with water
Accumulation
• the process in which water pools in large
bodies (like oceans, seas and lakes).
• Discharge area – outlets - areas where
water accumulates – geysers, streams,
oceans.
Evaporation
• the process in which liquid water becomes water
vapor (a gas). Water vaporizes from the
surfaces of oceans and lakes, from the surface
of the land, and from melts in snow fields.
• Transpiration - the process in
which some water within plants
evaporates into the atmosphere.
Water is first absorbed by the
plant's roots, then later exits by
evaporating through pores in the
plant.
Condensation
• the process in which water vapor (a gas)
in the air turns into liquid water.
Condensing water forms clouds in the
sky. Water drops that form
on the outside of a glass of
icy water are condensed
water. (This term appears
twice in the diagram.)
Water Pollution
Turgor Pressure
• Turgor Pressure: also called turgidity, is
the main pressure of the cell contents
against the cell wall in plant cells. Turgid
plant cells contain more water than flaccid
cells and exert a greater osmotic pressure
on its cell walls.
• Turgor is a force exerted outward on a
plant cell wall by the water contained in
the cell. This force gives the plant rigidity,
and may help to keep it erect. Turgor can
result in the bursting of a cell.