Temperature, Heat,
and Thermal Energy
Heat
• The transfer of thermal
energy
• Not a measure of energy but
rather of energy transferred.
• Measured in terms of joules
or calories (cal).
• Calories relate heat to
changes in temperature.
• Calorie is defined as the
amount of heat needed to
raise the temperature of one
gram of water by one degree
Celsius.
Specific Heat
• The correlation
between heat and
temperature.
• It measures how much
heat is required to
raise the temperature
of a certain mass of a
given substance.
• Every substance has a
different specific heat,
but it is constant for
that particular
substance.
Temperature
• A property of a material.
• Depends on the material.
• Measures the concentration of thermal
energy in an object in much the same way
that density measures the concentration of
matter in an object.
• A large object will have a lower temperature
than a small object with the same amount of
thermal energy.
Temperature
• A measure of the average kinetic energy of the
molecules that make up that material.
• Solids are rigid because their molecules do not
have enough kinetic energy to go anywhere.
• The molecules in liquids have enough energy
to move around one another but not enough
to escape each other.
• Gas molecules have so much kinetic energy
that they disperse and the gas expands to fill
its container.
Solids, Liquids, and Gases
• When the temperature of a solid is raised, it will become a
liquid. At an even higher temperature, it will become a gas.
• This is explained by thermal energy.
– When the thermal energy of a solid is increases, the motion of the
particles is increased and the temperature increases. This added
thermal energy causes the particles to move rapidly so that their
motion overcomes the forces holding the particles together.
Solids, Liquids, and Gases
– At this point the substance has changed from a solid to a
liquid. This change occurs at the melting point.
– When a substance is melting, all of the added thermal energy
goes to overcome the forces holding the particles together in
the solid state.
– Once the solid is completely melted, there are no more
forces holding the particles in the solid state and the added
thermal energy again increases the particles motion and
causes the temperature to rise.
Solids, Liquids, and Gases
– At the boiling point, further addition for energy
causes another change of state where all the
added thermal energy converts the material from
the liquid state to the gas state.
Temperature is
Measured in:
• Celsius (oC)
– Water freezes at 0 oC
and boils at 100 oC
• Fahrenheit(oF)
– Temperature in the
United States is
measured in Fahrenheit
• Kelvins (K)
– A measure of absolute
temperature.
Thermal Energy
• The energy created by moving particles inside
a substance.
• More movement of particles=more thermal
energy
• More thermal energy=higher temperature
• Less thermal energy=lower temperature
• Always moves from hotter objects to cooler
objects.
Conduction
• The transfer of energy from one molecule to another.
• This occurs when molecules hit against each other.
• Takes place in solids, liquids, and gases, but works
best in materials that have simple molecules that are
located close to each other.
• Metal is a good conductor.
• The movement of heat by a liquid or gas.
• The liquid or gas moves from one location to
another, carrying heat along with it.
• This movement of a mass of heated liquid or
gas is called a current.
Convection
Radiation
• Heat travels from the sun.
• The transfer of heat by electromagnetic waves.
• When infrared rays strike a material, the material’s
molecules move faster.
Ocean Thermal Energy
Conversion
• The ocean’s thermal energy comes from the
sun which alters the temperature of the ocean
water.
• Ocean thermal energy can produce electricity
– It does this three different ways
• Closed-cycle
• Open-Cycle
• Hybrid System
• This system relies on low-boiling point fluids.
The warm ocean water is used to heat up an
boil these liquids, which turn a turbine. This
turbine produces electricity.
Closed-cycle
Open-Cycle
• This system relies on a low-pressure
environment to actually boil the ocean water
and create steam. This stem will turn a
turbine.
Hybrid System
• This system combines both the open and
closed cycle systems.
Commercial Applications for
Thermal Energy
• The thermal energy business deals with
energy conservation, efficient conversion, and
utilization of fossil fuels and other energy
resources.
• The main focus is on:
– Improving already existing technologies
– Manufacturing newer and better technologies
– Consulting
How Do Temperature, Heat, and
Thermal Energy Relate
• Temperature is the measure of heat.
• Heat is thermal energy that flows from a
warmer object to a cooler object.
• More thermal energy means a higher
temperature and less thermal energy means a
lower temperature.