Energy

Energy

• The ability to do work. • Work : a transfer of energy. • Both energy and work are measured in Joules J• Energy and work are related. When work is done on

an object energy is being transferred to the object.

Law of Conservation of Energy

• Energy can not be created nor destroyed only changed to a new form.

• Basically means in a closed system that amount of energy going in will equal the amount of energy coming out.

• In some situations energy may be lost due to friction forces and changed to heat.

Energy Conversions

• Energy can be converted from one form to another. Conversions are constantly occurring.

Types of Energy

• There are many forms of energy either renewable or non-renewable.

Types of Energy

• 1. Mechanical (kinetic or Potential)• 2. Thermal/Heat• 3. Chemical • 4.Electromagnetic• 5. Nuclear• 6. Electrical

Renewable

Mechanical Energy• Energy associated from motion and position of

everyday objects. • ME = KE + PE

Kinetic Energy

• Energy of motion. • KE = ½ MV²• Doubling mass = doubling KE• Doubling velocity = quadrupling KE

Potential Energy• Energy stored as position, shape, or condition.• Cello bow & arrow food fuel glycogen

• Two types:• 1. gravitational potential energy: based on height & mass

GPE = mgh m: mass g: acceleration due gravity h: height

m : kg g = 9.8 m/s² Earth

ht : m

To convert from mass to weight multiply by 9.8

Mass x 9.8 = Weight (N)

• 2. elastic: based on condition/elasticity.• The potential energy of an object that is

stretched or compressed. • Can spring back to its original shape after

being compressed or stretched.

Pendulums

• Some of our first clocks relied on pendulums that swung to keep time. It converted pe to ke.

• Pole vaults, roller coasters, skiing

Thermal EnergyWhen atoms move faster the Thermal Energy will increase and the object will become warmer.

Thermal Energy• Total P.E. + K.E.• depends on mass and temperature• Teapot vs. cup = teapot has more due to mass

of particles• Hot tea vs. Cold tea = hot has more due to

more K.E.

Heat (4T’s)

• Transfer of Thermal Energy from one object to another because of temperature differences.

• Always moves from Hot to Cold

Temperature (4E’s)

• How hot or cold an object is• Related to the average K.E. of particles in an

object• Due to their random motion

Specific Heat

• The amount of heat required in calories to raise the temperature of 1 g. by 1ͦͦ c

Specific Heat• Like iron, most substances have a specific heat lower than that of water, meaning that

less heat is needed to raise their temperature than is needed to raise the temperature of water by the same amount. Most liquids have a specific heat less than half that of water

and, in general, the specific heat of solids is lower than that of liquids.

Thermal Expansion

• An increase in volume of a material due to an increase in temperature .

• Particles move farther apart as temperature increases

• Gases expand the most

Calorimeter

• Used to measure changes in thermal energy.

Conduction

• Transfer of T.E. with no overall transfer of matter.

• Particles are touching.• Faster in solids than gases because collisions

are less. • Metals (conductors) conduct T.E. fast due to

movement of molecules which is more free.

Conductors

• Any material that easily transfers thermal energy.

• Best are metals such as gold and copper.

Insulators

• A material that conducts T.E. poorly.• Wood, plastic , rubber, air , foam cups• Wood heats slowly due to being a poor

conductor of T.E.• Air is used in double pane windows and wool

clothes as insulators.

Convection

• Transfer of T.E. when particles move from one place to another. Due to density and temperature.

• Convection currents occur when a fluid circulates in a loop as it alternates form heating up to cooling down.

• Examples: ocean current, weather systems, rocks

Radiation

• Transfer of Energy by waves moving through space.

• Heat lamps , microwaves, sun

Chemical Energy

• The energy stored in chemical bonds.• When bonds are broken, the released energy

can do work.• Wood is burned and energy is released as

heat.• Examples: fuel , coal, gas

Electromagnetic Energy

• Energy transferred through space in waves. • Examples: visible light, x-rays, gamma rays,

radio waves.

Nuclear EnergyThe energy stored in atomic nuclei.Nuclear power plant uses fission reactions by splitting nuclei apart. This process releases energy. Nuclear fusion releases energy when less massive nuclei combine to form a more massive nucleus.