Transcript What happens to a puddle on a sunny day?

What happens to a puddle on
a sunny day?
• On a sunny day, water from a
puddle evaporates.
• Evaporation is liquid water
dissolving into the air.
• It becomes water vapor.
• The water behaves like a gas,
but it does not change to
steam. (Have you ever seen a
puddle boil?)
• What happens to the water
vapor?
Clouds
Evaporation
• Imagine a mass of air
near the ground.
• Water is evaporating
into it. The air mass is
becoming more humid.
• At the same time, the
air is being warmed by
heat from the ground.
• What happens to warm
air?
What will happen to the
air as it rises?
• As you move up
through the
troposphere,
temperature
decreases.
• As the warm, humid
air rises, it begins
to cool.
Which holds more water vapor,
warm air or cold?
• Warm air holds more
water than cold, so as
the air rises and
cools, its relative
humidity increases.
• When the air mass’s
temperature reaches
the dew point, some
of the water vapor
has to condense.
Condensation
• Just like morning
dew, the water vapor
needs something to
condense on.
• Tiny droplets of water
begin to form around
any small piece of
dust, dirt, or smoke in
the air. (If the air is
cold enough, an ice
crystal forms instead.)
• The droplets are
small enough to float
in the air. (remember
colloids?)
Condensation
• Water begins to condense onto to a seed of dirt, dust,
etc. forming a droplet.
• As more water condenses onto the droplet it grows.
• In cold air, the water freezes to the seed, forming a snow
flake.
• Hailstones form in a similar way, but grow larger due to
high winds in thunderstorms.