Transcript Water and the Water Cycle

Water and the Water Cycle
STANDARDS
S4E3 – Students will differentiate between the
states of water and how they relate to the
water cycle and weather.
-Demonstrate how water changes states (ice) to liquid
(water) to gas (water vapor/steam) and changes from gas
to liquid to solid.
-Identify the temperatures at which water becomes a solid
and at which water becomes a gas.
-Investigate how clouds are formed.
-Explain the water cycle (evaporation, condensation, and
precipitation).
-Investigate different forms of precipitation and sky
conditions (rain, snow, sleet, hail, clouds, and fog)
What is the water cycle?
 The water cycle is a continuous cycle
where water evaporates, travels into the air
and becomes part of a cloud, falls down to
earth as precipitation, and then evaporates
again. This repeats again and again in a
never-ending cycle. Water keeps moving
and changing from a solid to a liquid to a
gas, over and over again.
What 3 forms can water take?
Water can occur in three states: solid (ice), liquid, or gas (vapor).
 Ice is a solid.
 Ice melts to form a liquid.
 Liquid evaporates to form a gas. This is
called water vapor.
 A change in temperature is what causes
liquids to change states.
Solid
 Solid water—ice is frozen water. When
water freezes, its molecules move farther
apart, making ice less dense than water.
This means that ice will be lighter than the
same volume of water, and so ice will float
in water. Water freezes at 0° Celsius, 32°
Fahrenheit.
Liquid
 Liquid water is wet and fluid. This is the
form of water with which we are most
familiar. We use liquid water in many ways,
including washing and drinking.
Gas
 Water as a gas—vapor is always present in the
air around us. You cannot see it. When you boil
water, the water changes from a liquid to a gas or
water vapor. As some of the water vapor cools, we
see it as a small cloud called steam. This cloud of
steam is a mini-version of the clouds we see in the
sky. At sea level, steam is formed at 100° Celsius,
212° Fahrenheit.
 The water vapor attaches to small bits of dust in
the air. It forms raindrops in warm temperatures. In
cold temperatures, it freezes and forms snow or
hail.
Degrees
 Liquid water freezes at 0 degrees (32
degrees F).
 Liquids boil at 100 degrees C.
Water Cycle
 Water cycle is the cycling of water between Earth’s
waters, atmosphere, and land.
 Water cycle starts with the sun.
 Heat from the sun causes evaporation of water
from the Earth’s surface. The water rises and
cools.
 The water vapor in the air then condenses
(condensation). Clouds form as this point. They
form as droplets of water that condense around
dust in the air. If the droplets become heavy
enough, they become precipitation. Precipitation
is any form of water that falls from clouds to Earth
(rain, hail, snow, sleet, freeing rain).
Precipitation
 Rain comes from stratus and nimbostratus clouds.
Rain is formed from tiny cloud droplets come
together to form raindrops. Ice particles melt into
raindrops as they fall through warmer parts of the
atmosphere. Thunder showers fall from
cumulonimbus clouds.
 Snow falls from cold clouds where water vapor
becomes crystals of ice. The ice crystals stay
frozen as they fall.
 Sleet comes from small particles of ice that form
when rain falls through a layer in the atmosphere
that is above freezing, and then through a freezing
layer closer to the ground.
 Hail is hard, round ice pellets that form in large
cumulonimbus clouds.
Precipitation cont….
 Fog is a stratus-like cloud that forms when
water vapor condenses into small water
droplets at or near the ground. It is not
precipitation.
 Water vapor is the gas form of water (water
in a glass will turn to water vapor if left out).
Cool Facts
 About 70% of the earth’s surface is covered
with water. Ninety-seven percent of the water
on the earth is salt water. Salt water is filled
with salt and other minerals, and humans
cannot drink this water. Although the salt can
be removed, it is a difficult and expensive
process.
 Two percent of the water on earth is glacier
ice at the North and South Poles. This ice is
fresh water and could be melted; however, it is
too far away from where people live to be
usable.
Cool Facts continued…
 Less than 1% of all the water on earth is
fresh water that we can actually use. We
use this small amount of water for drinking,
transportation, heating and cooling, industry,
and many other purposes.