• What is the law of conservation of energy?

• How is energy transformed and transferred?

• What are renewable and nonrenewable energy resources?

Energy Transfers and Transformations

• law of conservation of energy

• energy transfer• energy

transformation

Energy Transfers and Transformations

• work• open system• closed system• renewable energy

resource• nonrenewable

energy resource

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

In every energy transformation, some energy transfers to the environment.

Law of Conservation of Energy

The radiant energy that shines out of the flashlight cannot be greater than the chemical energy stored in the battery.

• 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.

• Come up with your own example of an energy transfer with your partners

Law of Conservation of Energy (cont.)

• 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.

• Come up with your own example of an energy transformation with your partners.

Law of Conservation of Energy (cont.)

Law of Conservation of Energy (cont.)

Identify an energy transfer and an energy transformation that occurs

when someone plays a guitar.

Law of Conservation of Energy (cont.)

Identify an energy transfer and an energy transformation that occurs

when someone plays a guitar.

Answer: Chemical energy in the cells is transformed to mechanical energy in the fingers, then transferred to the guitar strings.

Electric energy from the amp is converted into sound energy when the chords are struck.

• 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.)

• If a tennis player is holding a tennis ball before a serve, is she doing work on the ball?

–Recall that to do work a force must be working on an object.

• Come up with an example of work being done in your everyday life, with your partners.

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

• Energy transformations are inefficient because not all the energy that is transformed to another form of energy is usable.

• Lets go back to the flashlight. In a flashlight the transformation of chemical energy from the battery to radiant energy from the light bulb is inefficient. As the electric energy move through the circuit, some electric energy transforms to thermal energy. This makes the transformation inefficient, and this is why some bulbs are warm.

• With your partners: Explain the above transformation and why its inefficient.

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

• 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.

Systems

• 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.

Renewable Energy Resources

• 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.

Renewable Energy Resources (cont.)

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

• 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.

Renewable Energy Resources (cont.)

• 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.

Nonrenewable Energy Resources

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

What are renewable and nonrenewable energy resources?

What are renewable and nonrenewable energy resources?

Renewable: energy resource that is replaced as fast or fast than it is used

Nonrenewable: energy resource that is available in limited amounts or is used faster than can be replaced in nature

• Energy can be transferred and transformed, but it cannot be created or destroyed.

• Systems are classified as open systems or closed systems based on their interactions with their environment.

• Energy resources are classified as renewable or nonrenewable based on their abundance and availability.

A. conservation

B. work

C. closed system

D. open system

1. Which term refers to the transfer of energy that occurs when a force makes an object move in the direction of the force?

A. closed system

B. energy resource

C. geothermal energy

D. open system

2. A car’s engine is an example of which of these?

1. In most systems, no energy is transferred to the environment.

2. Some forms of energy are replenished naturally.

Do you agree or disagree?

NOW what do you think?

A. open system

B. solar energy

C. nonrenewable energy resource

D. renewable energy resource

3. Which is an example of biomass?