What is Energy?

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What is Energy?
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• Energy is the power to change things.
• Energy is the ability to do work.

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• The sun gives out light and heat energy.
• Lights use electrical energy.
• Batteries for flashlights use chemical energy.

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2 Kinds of Energy

• One is doing work and the other is waiting to do
  work.
• Kinetic and Potential Energy

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Potential Energy

• Energy that is waiting to do work may be
• Sitting above ground level
• Is compressed or expanded in some way
• Found in the attraction between atoms
• This is potential energy.

Potential Energy is stored energy which means it
has the ability to do work Examples -A
rubber band when you stretch it -A yo-yo before
you let it fall
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Kinetic Energy

• When we see energy doing work, it is pushing or
  pulling, glowing, or changing temperature.
• This is kinetic energy.

• Kinetic Energy is energy of motion
• Examples
• -A rubber band flying through the air
• -A yo-yo in motion

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Forms of Energy

• Mechanical energy
• Thermal energy
• Chemical energy
• Electrical energy
• Light energy
• Sound energy
• Nuclear energy

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Mechanical Energy

• Energy associated with the motion or position of
  an object.
• Examples
• A hammer uses mechanical energy to do work. The
  mechanical energy of the hammer gives it the
  ability to apply the force to the nail in order
  to move the nail.

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Thermal Energy

• Total energy of the particles in a substance or
  material.
• When the thermal energy of an object increases,
  particles move faster, making the temperature of
  the object rise.
• Example
• Ice cream melts when its thermal energy increases

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Chemical Energy

• Potential energy stored in chemical bonds.
• Examples
• Food that you eat
• Match used to light a candle
• Cells of your body

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Electrical Energy

• Moving electrical charges produce electricity.
• Examples
• Radios
• Lights
• Computers
• Static shock

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Electromagnetic Energy

• Energy that travels in waves.
• Examples
• Visible light
• Ultraviolet radiation
• Microwaves

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Nuclear Energy

• Energy stored in the nucleus of an atom and is
  released during nuclear reactions.
• Examples
• Sun
• Stars
• Nuclear Power plant

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What kinds of energy can you identify?

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Potential Energy Converted to Kinetic Energy
When stored energy begins to move, the object now
transfers from potential energy into kinetic
energy.
Standing still
Running
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Roller Coaster Fun
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• Stored potential chemical energy in a
  flashlights batteries becomes light energy when
  the flashlight is turned on.

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• Food is stored energy. It is stored as a
  chemical with potential energy. When your body
  uses that stored energy to do work, it becomes
  kinetic energy.

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• When you talk on the phone, your voice is
  converted into electrical energy, which passes
  over wires. The phone on the other end changes
  the electrical energy into sound energy through
  the speaker.

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• A television changes electrical energy into light
  and sound energy.

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Lets Review

• If you are holding a coin in your hand, what type
  of energy does it have?
• If you drop the coin into a piggy bank, what
  happens to the energy?

Potential, because it has the ability to do work.
It is transferred from potential to kinetic.
Dropping the coin changes the stored energy into
motion.
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• A Power Plant
• The energy transformation process is carried out
  in three stages
• Chemical energy in the fuel (gas or oil) is
  released as heat in the boiler when it burns with
  air.
• Heat converts water in boiler tubes to steam,
  which is then used to drive a turbine that
  converts energy into mechanical energy.
• Mechanical energy drives an alternator to produce
  electrical energy.

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Law of Conservation of Energy

• When energy changes form the total energy
  before and after is the same.
• When you turn on a car, the chemical energy in
  the gas is converted to mechanical energy in the
  engine and heat energy but all energy can be
  accounted for.

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Temperature

• Measure of the average kinetic energy of the
  individual particles in an object.

The particles of hot cocoa move faster than those
of chocolate milk. Which drink has particles
with the greater average kinetic energy?
Hot cocoa
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Heat

• Movement of thermal energy from a substance at a
  higher temperature to another at a lower
  temperature.
• Heat is thermal energy moving from a warmer
  object to a cooler object.

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How Is Heat Transferred?

• Heat is transferred by conduction, convection,
  and radiation.

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Conduction

• Heat is transferred from one particle of matter
  to another without the movement of matter itself.
• Example
• Think of a metal spoon in a pot on the stove.
  Fast particles of hot electric coil collide with
  slow particles of cool pot. Particles of pot
  collide with particles of water, which collide
  with particles of spoon. As the particles move
  faster, the metal spoon becomes hotter.

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Convection

• Heat is transferred by the movement of currents
  within a fluid (a liquid or gas).
• Example
• When water at the bottom of a pot is heated,
  particles move faster, and farther apart. Heated
  water is less dense so it rises to the top of the
  pot. The surrounding cooler water flows into the
  bottom of the pot in a circular motion called a
  convection current.

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Radiation

• Transfer of energy by electromagnetic waves.
• Radiation does not require matter to transfer
  thermal energy.
• Example
• You can feel radiation from a bonfire or heat
  lamp from a distance.