Energy and Energy Transformations

Learning Goals/Objectives The students will define energy and describe and give an example of 9 forms of energy The students will explain the Law of Conservation of Energy

What is Energy? Energy is the ability to do work on or cause a change in matter The Law of Conservation of Energy – Energy cannot be created or destroyed, only transformed from one form to another Energy Transfer versus Energy Transformation When one form of energy is converted into another form of energy Energy moves from one object to another without changing form Work- 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 an object.

Forms of Energy Kinetic – the energy of an object’s motion (a falling rock) Potential – stored energy due to an object’s position or shape (a catapult) Mechanical – the energy of an object’s position and motion (a pitched baseball) Chemical – the energy stored in chemical bonds (food, batteries) Thermal – the energy due to the random motion of atoms (cup of tea) Sound – the energy due to an object’s vibrations (plucked guitar string) Electrical – the energy of moving electrons/an electric current (a hairdryer that is plugged into the electrical socket) Light/Radiant – the energy carried by electromagnetic waves/vibrating electric charge (visible light, infrared rays) Nuclear – the energy stored in the nucleus of an atom (stars)

Potential and Kinetic Energy http://bishopcook09.wikis.birmingham.k12.mi.us Don’t forget, there is still potential energy at this point as well as thermal energy and sound energy Kinetic energy is transformed into thermal energy due to friction

Potential Energy Elastic Potential Energy Chemical PE Gravitational Potential Energy http://www.bbc.co.uk/schools/ks3bitesize/science/images/boulder.jpg

Gravitational Potential Energy The amount of GPE that an object has depends upon the mass of the object and the height of the object above the ground. In each scenario below, which of the objects has a greater potential energy? (GPE = mgh)

Chemical Energy http://i.ehow.co.uk/images/a04/bd/ic/chemical-energy-work-3.1-800X800.jpg

Thermal Energy http://energyboomer.typepad.com/.a/6a00d83451dceb69e200e553bcf40e8833-300wi Electrical energy converted to light energy and thermal energy http://www.solar-pools.net/images/solarpool.jpg Light/Radiant energy converted to thermal energy

Sound, Electrical, and Nuclear Energy Stored potential chemical energy in the battery is transformed into electrical energy when the circuit is closed http://www.physicscentral.com/experiment/physicsathome/images/drum.gif Sound energy is produced by vibrating matter http://www.solarsam.com/images/battery_circuit.JPG When the nuclei of Uranium atoms are split (fission), lots of energy is released heating water to steam to turn a turbine and generate electrical energy

Law of Conservation of Energy – Energy cannot be created or destroyed, only transformed from one form to another Potential chemical energy (stored in the coal) is transformed into thermal energy and then kinetic energy (spinning turbine) and then electrical energy. The electrical energy powers your appliances, computer, TV, hairdryer, etc. and is transformed into other forms of energy such as mechanical energy, light energy, thermal energy, sound energy. http://www.solpass.org/6-8Science/6s/Images/EnergyTransformations.gif

Energy Transformations are never 100% efficient, because some kinetic energy is always transformed into thermal energy or sound energy and is unavailable for further useful work The light bulb transforms electrical energy into light energy and thermal energy http://www.ems.psu.edu/~radovic/efficiency.gif Chemical energy transformed into mechanical energy, thermal energy, and sound energy

Renewable Energy Resources Renewable energy resource- an energy resource that is replaced as fast or faster than it is used Ex: Solar- Converted into electric energy in solar cells(photovoltaic cells) Sometimes transformed into thermal energy, which is used to convert water into steam; the steam turns the generator, which transforms mechanical energy into electric energy.

Wind- turbines use wind to turn a generator; changing kinetic energy to electric energy. Hydroelectric- the mechanical energy of falling water is channeled through a turbine and is transformed to electric energy Geothermal- thermal energy from within the earth is transferred to water, creating steam, which is used to turn turbines in electric generators. Burning Biomass-includes wood, plants, manure and garbage. Stored chemical energy is released and transformed to electric energy.

Nonrenewable Energy Resources Nonrenewable energy resources- energy resources that are available in limited amounts or are used faster than they are replaced in nature Ex: Fossil fuels Petroleum (oil) Natural gas Propane Coal Nuclear Energy

Writing Response Give an example of an energy conversion. Make sure to discuss which forms of energy are involved.

PARTICLES IN MOTION

KINETIC MOLECULAR THEORY The transfer of thermal energy depends on the movement of particles in the material. The Kinetic Molecular Theory of matter explains how particles move. Particles make up all matter Particles are in constant random motion Particles constantly collide with each other and with the walls of their container.

Temperature- the measure of the average kinetic energy of the particles in a material. If particles in a material have little kinetic energy, the material feels cold. SI Units- Kelvin (K) and Celsius (C) Thermal Expansion - the increase in the Volume that a material undergoes when its temperature increases. At higher temperatures, particles move faster, requiring more volume because they collide more often , pushing each other apart Thermal contraction-the decrease in a material’s volume when its temperature decreases.

Kinetic energy is transferred from one material to another when their particles collide. Heat is the movement of thermal energy from one region of higher temperature to a region of lower temperature Materials are said to be in thermal equilibrium when the temperature of the materials that are touching are equal.

Your Coke becomes cold because the heat from the soda http://www.photoanswers.co.uk/ImgGalleryTn/91/10191/2417_16333.jpg Your Coke becomes cold because the heat from the soda transfers into the ice, not the other way around.

Heat Transfer

Radiation Heat transfer by radiation is the transfer of heat through electromagnetic waves. There is no direct contact between the substances.

Conduction The transfer of thermal energy by the collisions between particles of matter. (through direct contact). Molecules transfer energy to the molecules next to them.

Convection Heat transfer by convection is the transfer of thermal energy (heat) through the fluid (liquids and gases) movement of currents.

Convection Warm fluids rise, cool down, sink, and then are warmed again.

WRITING RESPONSE Give example of conduction, convection, and radiation from your everyday life.

Heat & Changes Of State When thermal energy is added to solid ice, its temperature increases until it starts to melt, changing to liquid water.

When thermal energy is removed from liquid water, it’s temperature decreases until it starts to freeze, changing to solid ice.

When thermal energy is added to liquid water, its temperature increases until it starts to vaporize, changing to a gas

When thermal energy is removed from a gas, it changes to a liquid through a process of condensation.

Sublimation occurs when a solid absorbs energy and changes directly to a gas without becoming a liquid (ex: dry ice) Deposition- when a gas changes directly to a solid without first becoming a liquid.

Writing Response What are two ways to change the state of a substance?

Writing Response What are two ways to change the state of a substance? Two ways to change the state of a substance is by either adding or removing thermal energy.

Conductors & Insulators Thermal energy moves quickly in a thermal conductor Thermal energy moves slowly in a thermal insulator

Writing Response Indicate whether each object below is either a conductor or and insulator: Flannel shirt- Iron skillet- Copper pipe- Oven mitt-

Writing Response Indicate whether each object below is wither a conductor or and insulator: Flannel shirt- insulator Iron skillet- conductor Copper pipe-conductor Oven mitt- insulator