Heat Transfer
& Phases
Intro Chapter
Energy
• Is the ability to do work and cause a
change.
• Can be transferred.
– Gases and liquids are made of molecules that are
constantly moving (kinetic energy). The faster
they are moving the more energy they have.
– Solids- molecules vibrate close together and
transfer energy.
Heat
• The energy transferred from a hotter
object to a cooler one.
• Three ways it is transferred.
Thermal Energy
• Is the total energy of motion in the
molecules of a substance.
• Gases are made of molecules that are
constantly moving. The faster they are
moving the more energy they have.
Temperature
• The average amount of energy of
motion in the molecules of a
substance.
• It is a measure of how hot or cold
something is.
Speed of Molecules & Temp
•
What happens
to the speed of
the molecules
when
temperature is
increased?
Speed of Molecules & Temp
•
What happens
to the speed of
the molecules
when
temperature is
increased?
Speed of Molecules & Temp
•
What happens
to the speed of
the molecules
when
temperature is
increased?
Speed of Molecules & Temp
•
What happens
to the speed of
the molecules
when
temperature is
increased?
Phase Changes
•
When a substance changes from one
state or phase to another.
• Solids
• Liquids
• Gases
•
Always occur with a change in heat,
which is energy.
Solids
•
Have definite shape and volume
• Solid to liquid- melting
• Solid to gas- sublimation
Liquids
•
Has a definite volume, and is able to
take the shape of the container
holding it.
• Liquid to solid- Freezing
• Liquid to gas- vaporation
• Boiling and Evaporation
Gases
•
A state of matter without definite
shape or volume.
• Phase Change• Gas to liquid- condensation.
Remaining Time:
Remaining Time:
Remaining Time:
Remaining Time:
Remaining Time:
Remaining Time:
Radiation
Climate
• The direct transfer of energy
over long distances of empty
space.
• Moves in waves.
(Electromagnetic Waves)
• No direct contact
• Can not see it, but feel it a
heat (Infrared)
– Sunlight
– Open fire
Conduction
• Heat transfer by direct
contact of particles of
matter. (Transfer by
Touching)
• Particles bump into each
other and transfer their
energy heating them up.
– Putting your hand on a hot
stove.
Convection
• Heat transfer by the circular movement of a
fluid (liquids and gasses).
• Particles flow transferring heat energy.
• Caused by differences in density.
How Convection Works
• Density: the amount of mass in a given
volume. D=M/V
• Heated Fluids:
– Move faster and bump into other particles.
– They spread out increasing the volume.
– Density decreases
• Cooling Fluids
– Move slower
– They come together decreasing the volume.
– Density increases