What is energy?

1. 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.

2. 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: http://phet.colorado.edu/en/simulation/travoltage

3. 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.

4. 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. http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

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

6. 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.

7. 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

8. 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).

9. 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

10. 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

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

12. Light Energy • Refraction - bending of light as it travels through a different medium • Examples of items that refract light: Telescopes Microscopes Eyeglasses Water (liquids) Magnifying glass Cameras Prisms • We want to remember: Lens= bends

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

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

15. 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

16. 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.

17. 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.

18. 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.

19. 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