Transcript ENERGY

ENERGY
CHANGES AND
TRANSFORMATIONS
ENERGY
 Energy is the ability to cause change or
produce work.
 The word energy comes from the ancient
Greek energos which means active.
 Energy can change the shape of matter.
ENERGY
 Energy can change temperature, shape,
speed, or direction of an object.
ENERGY
 Energy comes in different forms from a
variety of sources.
 Examples; eating a succulent breakfast
provides energy to your body.
 A flame gives off energy in the form of
heat or light.
Form of Energy
Produced by
Examples
Chemical
Chemical react. Combustion
Heat
Friction
Mechanical
Movement
Tire skidding on
pavement
Waterfall
Light
Waves
X- rays, microwaves
Nuclear
Fission
Electrical
Electrons
Nuclear power
plants
Electricity
Sound
Sound waves
Speakers
Potential
Store in matter
Roller coaster car on top of
the hill
Kinetic
Motion
Hiking
Mechanical Energy
Chemical Energy: Combustion
ENERGY
Conserving Energy
 In 1840 James Joules described the Law
of Conservation of Energy. Energy can
not be created or destroyed. It only can
be transform from one form into another.
 This concept means that the total
amount of energy in the universe is
constant.
KINETIC ENERGY
 The amount of kinetic energy in an
object is determined by the mass and
speed of the object.
Potential and Kinetic Energy
 KE = (mass x velocity2)/2 or 1/2 mv2
 KE = 1/2 mv2
 GPE = weight x height
 PE= weight x h
 Weight = mass x gravity
ENERGY
 Human body changes chemical energy
of food into mechanical energy to
move the muscles.
 Nuclear power plants convert the energy
stored inside some atoms into electrical
energy.
 Although the total amount of energy is
the same before and after energy
transfer; some amount of energy is lost
as heat during the exchange.
ENERGY
 Mrs. Weiler puts gasoline in her car and drives
it home. What energy change has occurred?
A. Burning the gasoline in the car has created new
energy to make the car run.
B. Burning the gasoline has destroyed energy.
C. The chemical energy in the gasoline has been
changed into mechanical energy to turn the
engine and other parts of the car.
D. There has been no change in the amount of
form of energy.
ENERGY
Temperature
 Any material or object is made up of
particles that are invisible to the naked
eye. The particles that make up any
object are constantly moving. Therefore,
they are in constant motion. They have
kinetic energy.
ENERGY
 Temperature is the measure of the average
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kinetic energy of the particles in an object.
The greater the AKEP is, the higher an object’s
temperature is.
Temperature scales:
Celsius
Fahrenheit
Kelvin
Rankine
ENERGY
 Gabriel Fahrenheit ( 1686- 1736) a German
physicist developed the scale and an accurate
thermometer by using mercury.
 Celsius is the scale temperature used for
people in the majority of countries of the world
except United States.
 Kelvin scale is related with Celsius scale.
 Lord Kelvin ( 1824- 1907) introduce a
temperature scale that begins at ABSOLUTE
ZERO.( -273.15 C or -459.67 F )
ENERGY
TEMPERATURE
FREEZING POINT
BOILING POINT
CELSIUS
0
100
FAHRENHEIT
32
212
KELVIN
273.15
373
ENERGY
 THERMAL ENERGY is the total amount
of kinetic energy of the particles in a
material.
 The movement of thermal energy from a
warmer object to a cooler one is called
HEAT.
 THERMAL ENERGY moving by
radiation travels by waves in all
directions.
ENERGY
 Radiation is the energy that travels by
waves in all directions from its source.
 Radiation can travel through air and
space.
 The sun transfers energy through
radiation.
 The microwave of your kitchen transfers
radiation.
Radiation
 Radiation is transfer by electromagnetic
waves, those come in contact with the
object and transfer heat to the object.
Electromagnetic spectrum
ENERGY
 Conduction is the transfer of thermal
energy from particle to particle through a
material when is a temperature
difference. ( collision of particles )
 Example: heating a ham and cheese
sandwich on a skillet or a pan and using
the stove.
 Thermal energy is transferred to the pan,
bread, cheese and ham.
Conduction
 Transfer of heat between substances
that are in direct contact with each other.
ENERGY
 METALS are good conductors of electricity.
 Insulators are materials that do not allow
thermal energy to be conducted easily.
 Examples of insulators: plastic, rubber, wood,
Styrofoam.
Convection
 Convection transfers thermal energy
when particles move from one place to
another where there is a difference of
temperature.
 Convection is the primary method by
heat moves through gases and liquids.
Convection
ENERGY
 Example of convection, air conditioning
system.
 Convection causes warm and cool
currents in the atmosphere, which
produce Earth’s weather.
 The effects of warm and cool air currents
are important in the formation of
hurricanes and tornados.
Review of Concepts
 Temperature is …………………..
 The more kinetic energy the molecules
have, the ………… the temperature.
 Heat is the thermal energy that moves
from one object to another when the
objects are at ………… temperature.
 Thermal energy moves when two objects
are in ………….with each other.
HURRICANES
 A tropical cyclone's primary energy source is
the release of the heat of condensation from
water vapor condensing at high altitudes, with
solar heating being the initial source for
evaporation. Therefore, a tropical cyclone can
be visualized as a giant vertical heat engine
supported by mechanics driven by physical
forces such as the rotation and gravity of the
Earth.
HURRICANES
 The ingredients for a hurricane include a
pre-existing weather disturbance, warm
tropical oceans, moisture, and relatively
light winds aloft. If the right conditions
persist long enough, they can combine
to produce the violent winds, incredible
waves, torrential rains, and floods we
associate with this phenomenon.
HURRICANES
ENTROPY
Ice melting is a common example of "entropy increasing"[
described in 1862 by Rudolf Clausius as an increase in
the disgregation of the molecules of the body of ice.
ENTROPY
 Entropy represents the "potential for
disorder" in a system.
ENTROPY
ENTROPY
 If you assert that nature tends to take things
from order to disorder and give an example or
two, then you will get almost universal
recognition and assent.
ENTROPY
 It is a part of our common experience.
You spend hours cleaning desk, room,
house, and it seems to spontaneously
revert back to disorder and chaos before
your eyes blink. So if you say that
entropy is a measure of disorder, and
that nature tends toward maximum
entropy for any isolated system.
Review:
 Thermal energy is transferred from
…….. to…………….objects.
 There are three ways when transferring
thermal energy : 1………………2……….
 3……………….
 Conduction occur when the
particles…………..with each other.
 Conduction works best in 1………..
 2…………………
Review:
 Radiation is the transfer of thermal
energy by ……………..waves.
 Radiation transfers energy through
…………….. …………….
 Convection is the transfer of thermal
energy by the …………..of molecules
from one part of a material to another.
Thermal Energy
 Conductor is any material in which
thermal is transferred quickly.
 Example some metals.
 Insulator is a poor conductor of thermal
energy.
 Example: cardboard, Styrofoam.
 Thermal pollution is the increase in
temperature of a body of water caused
by adding warmer water.
Themodynamics
 A Zeroth Law?
 Law Number Zero! Here's what it says:
When two systems are sitting in
equilibrium with a third system, they are
also in thermal equilibrium with each
other.
A Zeroth Law
First Law of Thermodynamics
 The first law states that when heat is
added to a system, some of that energy
stays in the system and some leaves the
system. The energy that leaves does
work on the area around it. Energy that
stays in the system creates an increase
in the internal energy of the system.
First Law of Thermodynamics
Second Law of
Thermodynamics
 The second law of thermodynamics
explains that it is impossible to have a
cyclic (repeating) process that converts
heat completely into work. It is also
impossible to have a process that
transfers heat from cool objects to warm
objects without using work.
Second Law of
Thermodynamics
Third Law of Thermodynamics
 It is impossible to reduce any system to
absolute zero in a finite series of operations.
 The entropy of a perfect crystal of an element
in its most stable form tends to zero as the
temperature approaches absolute zero.
 As temperature approaches absolute zero,
the entropy of a system approaches a
constant.
Third Law of Thermodynamics
 In physics, absolute zero is considered the lower limit for
the temperature of any system, and the third law of
thermodynamics can be formulated in terms of this
temperature.
 The third law of thermodynamics is pretty straightforward
— it just says that you can’t reach absolute zero (0 kelvin,
or about –273.15 degrees Celsius) through any process
that uses a finite number of steps. In other words, you
can’t get down to absolute zero at all. Each step in the
process of lowering an object’s temperature to absolute
zero can get the temperature a little closer, but you can’t
get all the way there.