16.2 Heat and Thermodynamics
Conduction
Conduction is the transfer of thermal energy with no
overall transfer of _______________.
Conduction in gases is ________ than in liquids and
solids because the particles in a gas collide less
often.
16.2 Heat and Thermodynamics
Conduction
• Conduction occurs within a material or between
materials that are _________________.
• In conduction, collisions between particles transfer
thermal energy, without any overall transfer of matter.
• A thermal conductor is a material that conducts
thermal energy __________.
• A material that conducts thermal energy poorly is
called a thermal _________________.
16.2 Heat and Thermodynamics
Conduction
The arrows show how thermal energy is
conducted away from the heat source in a
metal frying pan.
16.2 Heat and Thermodynamics
Conduction
• ____________ are good thermal conductors.
–When a frying pan is on a hot stove, the bottom of
the metal pan heats first and the metal handle last.
The flames do not directly heat the handle.
–Tile is a better conductor than wood. A tile floor feels
colder than a wooden floor when both floors are at
room temperature. The tile transfers thermal energy
more rapidly away from your skin.
• __________ is a very good thermal insulator.
–Wool garments and plastic foam cups use trapped air
to slow down conduction.
16.2 Heat and Thermodynamics
Convection
Convection is the transfer of thermal energy when
particles of a______move from one place to another.
• Convection currents are important in many natural
cycles:
• __________ currents
• weather systems
• movements of _____________in Earth’s interior
16.2 Heat and Thermodynamics
Convection
A. Passing sandbags along a line is like
transferring thermal energy by convection.
B. The arrows show convection of air in an oven.
16.2 Heat and Thermodynamics
Convection
A convection current occurs when a fluid ________
in a loop as it alternately heats up and cools down.
• Air at the bottom of an oven heats up, expands,
and becomes less dense. The hot air rises.
• Rising hot air cools as it moves away from the
heat source.
• As a result, the coolest air is at the top of the
oven.
16.2 Heat and Thermodynamics
Radiation
Radiation is the transfer of energy by______moving
through space.
• _______ objects radiate energy.
• As an object’s temperature increases, the rate at
which it radiates energy ______________
16.2 Heat and Thermodynamics
Radiation
When you stand to the side of a charcoal grill, heat
reaches you without convection or conduction.
The sun warms you by radiation on a clear day. The
space between the sun and Earth has no air to
transfer thermal energy.
Heat lamps used in restaurants are another example
of radiation.
16.2 Heat and Thermodynamics
Radiation
The heating coil on a
stove radiates thermal
energy.
The changing color of the
red arrows indicates that
the farther you are from
the coil, the less radiation
you receive.
16.2 Heat and Thermodynamics
Thermodynamics
• The study of___________between thermal energy and
other forms of energy is called thermodynamics.
• James Prescott______measured the energy changes
in a system (a group of objects that interact with one
another).
–Joule's system included a falling weight turning a paddle
wheel in water.
– Joule found that the work done by the falling weight almost
exactly equaled the thermal energy gained by the water.
– He is given credit for discovering the_____law of
thermodynamics
16.2 Heat and Thermodynamics
Thermodynamics
First Law of Thermodynamics
The first law of thermodynamics states that energy
is ________________.
• Energy cannot be created or destroyed, but it
can be _________________into different forms.
• Added energy increases the thermal energy of a
system or does work on the system.
• In either case, energy is conserved.
16.2 Heat and Thermodynamics
Thermodynamics
• Pushing on the pump does
work on the system.
– Some of the work is used to
compress air into the tire
– Some is converted into
thermal energy, which heats
the air in the pump and the
tire.
16.2 Heat and Thermodynamics
Thermodynamics
Second Law of Thermodynamics
The second law of thermodynamics states that
thermal energy can flow from colder objects to
hotter objects only if ____ is done on the system.
Thermal energy flows ___________ only from hotter
to colder objects.
• A refrigerator must do work to transfer thermal
energy from the cold food compartment to the warm
room air.
• The thermal energy is released by coils at the
bottom or in the back of the refrigerator.
16.2 Heat and Thermodynamics
Thermodynamics
___________: any device that converts heat into work
• The efficiency of a heat engine is always less than
______%.
• Thermal energy that is not converted into work is
called ___________heat.
• Waste heat is lost to the surrounding environment.
16.2 Heat and Thermodynamics
Third Law of Thermodynamics
The third law of thermodynamics states that absolute
zero_______________be reached.
The efficiency of a heat engine increases with a
greater difference between the high temperature
inside and the cold temperature outside the engine.
A heat engine could be 100 percent efficient if the cold
outside environment were at absolute zero (0 Kelvin).
This would violate the third law of thermodynamics.