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.

• 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

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.

– 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.

Solids, Liquids, and Gases

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.

• 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.

Thermal Energy

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.

Convection

• 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.

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

Closed-cycle

• 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.

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.