What is energy? Energy is the ability to do work or cause a change. Energy has many forms. Even though one form can change into another form, energy cannot be made or destroyed. Different forms of energy, including mechanical, light, thermal, electrical, and sound energy, have many uses.

Electrical Energy  Electrical energy is the movement of electrons.  Electrons are the negatively charged particles in atoms.  They can move easily from one object to another.  When an object has more electrons than protons, it becomes negatively charged.  When an object has more protons than electrons, it becomes positively charged.  The charge that results from a gain or loss of electrons is called an electric charge.  Just for fun:

Electrical Energy  Batteries store chemical energy and are often used to power circuits (converting chemical to electrical energy)  Electrons flow from the negative end (-) to the positive end (+).  You can remember this by thinking about taking away electrons from the negative end (-) and adding electrons to the positive end (+).  Electrical Energy is achieved by creating a complete or closed circuit. Circuit = wires connected to a power source  Breaks in a circuit cause the energy flow to STOP! This results in an open circuit.

Electrical Energy Series Circuit - one path for electrons. If one light burns out, they all go out because the circuit is broken (or open). Parallel Circuit- each light bulb has a separate path for the electrons to travel on If one light bulb burns out, the others stay lit because the electrical current can continue to flow.

Sound Energy  Sound energy is produced by vibrations and travels in waves. Sound= vibrations  Vibrations travel from the origin of the sound outward.

Sound Energy  Wave frequency determines the pitch of the sound. High pitched sounds have waves that travel very quickly together. Low pitched sounds are produced by sound waves that travel further apart.  The amplitude of a sound wave determines how loud or quiet a sound is.

Sound Energy  Sound only occurs when there are molecules for the sound to travel through.  Since there are no molecules in deep space between the stars and planets, there is no sound. This is called a vacuum.  Sound can travel through all states of matter- solids, liquids, and gases.  Sound travels through each substance at different rates. Solids are the best medium for sound to travel through.  A medium is the matter that energy (sound, light, etc.) is passing through.  iknowthat.com iknowthat.com

Sound Energy  Animals use sound as a means of communication.  They use sounds to:  Acquire food  Interact with members of their species  Claim or defend their territory  Respond to predators  Alert members of their community of danger  Attract a mate  Some animals use echolocation to find their way. This is especially important for marine animals (such as dolphins) and nocturnal animals (such as bats).

Sound Energy  Sound waves above the range of human hearing are called ultrasound.  Sound Inventions:  Sound energy is used in sonar devices to locate objects underwater and to map the sea floor.  Sound energy is also used in medicine to create sonograms.  Cool Website with lots of sound information Cool Website with lots of sound information

Light Energy  Light energy moves in waves and always travels in a straight line or a ray.  The Sun is the source of light energy for the Earth.  Objects reflect the colors we see and absorb other colors.  Plants reflect green light. That is why they appear green to us.  An apple reflects red light and absorbs all other colors.  Black = absorption of all colors  White = reflection of all colors

Light Energy  Reflection- when energy bounces back at the same angle Examples of objects that reflect light:  MirrorsMetalsTV Screens CD/DVDs Other Shiny Objects (contd.)

Light Energy  Refraction - bending of light as it travels through a different medium  Examples of items that refract light: TelescopesMicroscopesEyeglasses Water (liquids)Magnifying glassCameras Prisms  We want to remember: Lens= bends

Light Energy  Absorb- When light is blocked and absorbed by an object (not allowed to pass through)  Examples-  A brick wall  The color black

Light Energy  Transmit- when light is able to pass through a medium  Examples- A window A clear plastic

Light Energy  Some materials will affect light in multiple ways  Example – tinted windows/lenses will reflect some light rays and allow others to pass through.  Materials that block light are called opaque  Materials that allow light to pass through are transparent  Materials that scatter light are translucent

Mechanical Energy  Mechanical Energy is the energy of movement that does work.  Examples:  Raising a flag 2. Peddling a bike 3.Turning a crank  Mechanical energy usually involves a simple machine. (Review your vocabulary on simple machines from Unit 7)  Simple machines are used to help make work easier by reducing the effort needed to move a load or change its direction. They make it possible for people to do things they could not do with their hands alone.  Work is using a force to move an object a distance – in other words, the total amount of effort needed to move something.

Thermal Energy  Thermal Energy is the energy of heat.  It causes a change in the temperature between materials and always travels from the warmer material to the colder material  Adding or subtracting thermal energy can cause a change of the state of matter (solid – liquid – gas).  The main source of thermal energy is the sun. This thermal energy is necessary for all life on Earth.

Other Forms of Energy  Kinetic - energy that is in motion  Potential - energy stored in a system or energy that is the result of an object’s position  Gravitational potential energy - a type of stored energy that is a result of an object’s height and mass.  Chemical energy - energy that is produced by the rearrangement of electrons in atoms and molecules as in a chemical reaction.

Other Forms of Energy  Nuclear - the type of energy that is produced when the nucleus of an atom is split or combined with another atom.  Geothermal - energy that comes from the Earth’s heat  Hydro - energy from water (hydroelectric- running water is used to create electricity)  Solar- energy from the Sun  Wind- energy produced by capturing the wind’s power using wind turbines