II. Heat Energy
• A. Temperature is a
• B. Heat is a measure of
measure of how fast
the energy of an entire
the molecules hitting
SYSTEM. Units are
the thermometer are.
calories and joules.
Units are Fahrenheit, • Heat is calculated and
Celsius and Kelvin. It is depends on mass,
a direct measurement.
specific heat and
temperature.
Weather unit
C. Heat Capacity Page 1 ESRT: specific heats of common
materials
• 1. Specific heat is the energy (joules) that you must add to
increase the temperature of 1 gram of a substance 1 degree
Celsius.
• 2. Water has a high specific heat. It takes more than 5 times
as much energy to change the temperature of a gram of water
as to change the temperature of a gram of granite.
Weather unit
D. Comparing land and water
Land tends to:
Water tends to:
• Heat quickly and cool
• Heat slowly (absorption)
quickly.
and cool slowly
• Dry areas have huge
(reradiation).
changes in temperatures.
• Water moderates the
• Land is opaque; only the top
temperatures around it.
layers are directly heated.
• Water absorbs a lot of heat
• It has a low specific heat.
because it:
 is transparent,
 has a high specific heat,
 moves and
 evaporates.
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E. Heat Transfer
Energy is exchanged when a source of energy transfers that
energy to a substance.
• Conduction: molecule to molecule through vibration (solids
and surfaces)
• Convection: in fluids, due to density differences
• Radiation: electromagnetic energy travels in waves , through
space or materials.
Weather unit
http://www.spectrose.com/modes-of-heat-transfer-conduction-convection-radiation.html
III. Energy and Phase Changes
A. To change ice to water at 0
degrees C,
334 joules/gram must be
added.
• To change liquid to ice,
334 joules/gram must be
removed.
How do you remove heat?
it must be ‘lost’ or ‘given’ to
the environment.
Weather unit
uwsp.edu
B. Phases of water: p. 1 ESRT properties of water
• Phase describes the motion of the
molecules:
• Gases are independent and
move apart
• Liquids flow, but stay together
• Solids are locked in place.
• Since movement takes energy,
solids are the ‘coldest’
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C. Water phase change diagram
• Phase change diagram
of water can be viewed
‘forward’ (adding heat)
or ‘backward’ (removing
heat).
• Flat lines indicate phase
changes.
• Sloped lines indicate
temperature change.
• Condensation warms the air
around it
• Evaporation cools the air
around it.
Weather unit
Kentchemistry.com
D. Water is Weird: density
michitravel.com
• Density of water: at 3.98
degrees C, water is its
most DENSE!!!
the density is 1.0 g/ml
• At 0 degrees C, the
density of water is less
and ice floats!!!!!
• Water vapor: the hotter it
is, the lighter it is.
so, hot air rises….
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• E. Hot air: expands
(takes up more room)
and is lighter (rises) and
water evaporates
(vapor is light)
• Cold air: condenses
(molecules close
together) and water
vapor changes phase
into water drops.
http://science-mattersblog.blogspot.com/2010/08/air-pressure-balloon-
Weather unit
in-flask.html