ENERGY CHANGES AND TRANSFORMATIONS. ENERGY Energy is the ability to cause change or produce work. The word energy comes from the ancient Greek energos.

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 Tire skidding on pavement

Mechanical Movement Waterfall

Light Waves X- rays, microwaves

Nuclear Fission Nuclear power plants

Electrical Electrons 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 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.