Energy Lesson 1-1€¦ · Lesson 2-1 •To a scientist, work is the transfer of energy that occurs when a force makes an object move in the direction of the force. Work is only being

Lesson 1-1• Energy influences everything in your life,

including the climate, the economy, and your body.

• Scientists define energy as the ability to cause change.

Energy

Lesson 1-2• Potential energy is stored energy due

to the interaction between objects or particles.

• Objects have potential energy if they have the potential to cause change.

Potential Energy

Lesson 1-2Objects have gravitational potential energy if they have mass and height above Earth’s surface.

Lesson 1-2• Chemical energy is the energy stored in and

released from the bonds between atoms.

• Your body breaks chemical bonds in foods and coverts the released energy into other forms of energy that your body can use.

Potential Energy (cont.)

Lesson 1-2• The energy stored in and released from the nucleus

of an atom is called nuclear energy.

• The Sun’s energy is released through the process of nuclear fusion, during which the nuclei of atoms join together and release large amounts of energy.

Potential Energy (cont.)

Lesson 1-3• Kinetic energy is energy due to motion.

• An object’s kinetic energy is related to the mass and the speed of the object.

• The energy in an electric current is electric energy.

Kinetic Energy

Lesson 1-4

The sum of the potential energy and the kinetic energy in a system is mechanical energy.

Combined Kinetic Energy and

Potential Energy

mechanical

from Greek mēchanē, means “machine”

Lesson 1-4

• An object’s thermal energy is the sum of the kinetic energy and the potential energy of the particles that make up the object.

• Thermal energy of an object increases when the potential energy, the kinetic energy, or both increase.

Combined Kinetic Energy and

Potential Energy (cont.)

Lesson 1-4• A wave is a disturbance that transfers energy from

one place to another without transferring matter.

• Sound energy is carried by sound waves.

• The energy carried by electromagnetic waves is radiant energy.

Energy Carried by Waves

Lesson 1-4Electromagnetic waves often are described by their wavelengths—the distance from one point on a wave to the nearest point just like it.

Lesson 1-4Visible light is one form of radiant energy.

Lesson 2-1The law of conservation of energy says that energy can be transformed from one form to another, but it cannot be created or destroyed.

Law of Conservation of Energy

Lesson 2-1The law of conservation of energy indicates that the amount of radiant energy that shines out of the flashlight cannot be greater than the chemical energy stored in the battery.

Lesson 2-1• When energy moves from one object

to another without changing form, an energy transfer occurs.

• The mechanical energy of a tennis racket changing the movement of the ball is an example of an energy transfer.

Law of Conservation of Energy (cont.)

Lesson 2-1• When one form of energy is converted

to another form of energy, an energy transformation occurs.

• The conversion of chemical energy stored in a tennis player’s muscle changing to mechanical energy when she swings her arm is an example of an energy transformation.

Law of Conservation of Energy (cont.)

Lesson 2-1• To a scientist, work is the transfer of energy that

occurs when a force makes an object move in the direction of the force. Work is only being done while the force is acting on the object.

• Any time there is an energy transformation or energy transfer, some energy is transformed into thermal energy.

Law of Conservation of Energy (cont.)

Lesson 2-1• Because energy transformations are inefficient,

some of the chemical energy transforms to thermal energy and sound energy that are released to the environment.

• An open system is a system that exchanges matter or energy with the environment.

Law of Conservation of Energy (cont.)

Lesson 2-1• A closed system is a system that does not exchange

matter or energy with the environment.

• In reality, there are no closed systems because every physical system transfers some energy to or from its environment.

Law of Conservation of Energy (cont.)

Lesson 2-2

• A renewable energy resource is an energy resource that is replaced as fast as, or faster than, it is used.

• Solar energy from the Sun is one type of renewable energy resource that can be converted into electric energy.

Energy Transformations and

Electric Energy

Lesson 2-2

• Wind moves the blades of a wind turbine to generate electric energy.

• In hydroelectric plants, falling water is channeled through a turbine which transforms mechanical energy into electric energy.

Energy Transformations and

Electric Energy (cont.)

Lesson 2-2

• Geothermal plants transfer thermal energy from the Earth to water, creating steam that turns turbines in electric generators.

• Biomass includes wood, plants, manure, and garbage, all of which are sources of stored chemical energy that can be transformed to electric energy in energy plants.

Energy Transformations and

Electric Energy (cont.)

Lesson 2-2

• Nonrenewable energy resources are energy resources that are available in limited amounts or that are used faster than they can be replaced in nature.

• Fossil fuels include petroleum, natural gas, propane and coal.

• In nuclear energy plants, uranium atoms are split apart in a process called nuclear fission.

Energy Transformations and

Electric Energy (cont.)

Lesson 2-2Most of the energy used in the United States comes from nonrenewable energy resources.

Lesson 3-1• The kinetic molecular theory explains how particles

move and has three major points:

•All matter is made of particles.•Particles are in constant, random motion.•Particles constantly collide with each

other and with the walls of their container.

Kinetic Molecular Theory

Lesson 3-1Particles that make up all matter are in constant motion. On average, solid particles move slowest, liquid particles move faster, and gas particles move the fastest.

Lesson 3-1• The measure of the average kinetic energy of the

particles in a material is temperature.

• When the particles that make up a material move slowly, they occupy less volume than they do at a higher temperature.

• Thermal expansion is the increase in volume of a material due to a temperature increase.

Kinetic Molecular Theory (cont.)

Lesson 3-1When water is cooled to near its freezing point, interactions between water molecules push the molecules apart.

Kinetic Molecular Theory (cont.)

Lesson 3-1• As the kinetic energy of the particles

that make up a material increases, the thermal energy of the particles increases.

• As the kinetic energy of the particles that make up a material decreases, the thermal energy of the particles decreases.

Kinetic Molecular Theory (cont.)

Lesson 3-1When you put a warm bottle of water in a cold refrigerator, thermal energy is transferred.

Lesson 3-1• The movement of thermal energy from a region of

higher temperature to a region of lower temperature is called heat.

• When the temperatures of materials that are in contact are the same, the materials are said to be in thermal equilibrium.

Kinetic Molecular Theory (cont.)

Lesson 3-2• Conduction is the transfer of thermal energy by

collisions between particles in matter.

• Radiation is the transfer of thermal energy by electromagnetic waves.

• Convection is the transfer of thermal energy by the movement of the particles from one part of a material to another.

Heat Transfer

Lesson 3-2Conduction, radiation, and convection are ways in which thermal energy is transferred.

Lesson 3-3• Melting is the change of state from a solid to a

liquid.

• Freezing is the change of state from a liquid to a solid.

Heat and Changes of State

Lesson 3-3• Vaporization is the change of state from a liquid to

a gas.

• Vaporization that occurs within a liquid is called boiling.

• Vaporization that occurs at the surface of a liquid is called evaporation.

Heat and Changes of State (cont.)

Lesson 3-3• Sublimation is the change of state that occurs when

a solid changes to a gas without passing through the liquid state.

• Deposition is the change of state from a gas directly to a solid without passing through the liquid state.

• Water vapor undergoes deposition when it freezes and forms frost.

Heat and Changes of State (cont.)

Lesson 3-4• A thermal conductor is a material in which thermal

energy moves quickly.

• A thermal insulator is a material in which thermal energy moves slowly.

Conductors and Insulators