Download The Water Cycle The water on our planet circulates constantly

The Water Cycle
The water on our planet circulates constantly through our
atmosphere and has a big effect on our weather.
Major steps of the water cycle:
 Water evaporates from bodies of water, like oceans, rivers, lakes, etc
when those bodies of water are heated up by solar radiation
 This water vapor is now in the air and forms clouds during condensation
 During precipitation, water is returned to bodies of water
Other terms to know:
 Plants release water into the atmosphere during transpiration
 Runoff is precipitation water than runs over land on its way back to a
body of water
Details:
 Evaporationo An increase in energy (from solar radiation) causes water
molecules to move faster, fast enough to change states of matter
from a liquid to a gas
o Water (liquid) changes into water vapor (gas)
o Warm air above surface of Earth has molecules that are more
spread out (less dense!), which means there is room for water
vapor molecules
o This water vapor then rises with the rising warm air during
convection currents
 Condensationo The rising air during convection currents starts to cool off
o Because the air molecules then lose energy, they start to slow
down, move closer together, and the air becomes more dense
o As the air continues to cool, the molecules move so close together
that there is no more room left between them
o This air is referred to as saturated, or full, and this temperature
is its dew point
o When air cools past its dew point, the air molecules squeeze
together so much that they force the water vapor molecules out
of the air mass!
o The water vapor molecules have also lost energy due to cooling
down, and when they are forced out, they condense, or turn back
into a liquid
o Water molecules need a solid surface to condense onto, and
particles in the atmosphere like dirt, soot, dust, and volcanic ash
provide those surfaces
o Water molecules cling together to form clouds
 Precipitationo Eventually, clouds become very heavy, due to all those clinging
water drops
o Precipitation is water (in four different forms) falling from clouds
 Rain – liquid water drops
 Sleet – rain that passes through a layer of below freezing air
on its way down to the ground
 Snow - solid crystals falling from high-altitude clouds made
of ice
 Hail – round pieces of ice formed when frozen drops continue
to get blown by updrafts back up through below freezing air,
which freezes clinging rain drops, making ices pieces bigger