Ms. BrownMs. Brown8th Grade General Science8th Grade General Science

Jennifer C. Brown

Energy is the ability to “do work” and describes the ability of things to change or cause change in other things. • Work is done when a force moves an object over a

distance.

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You do 1 joule of work if you push with a force of 1 newton for a distance of 1 meter.

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(joules- J) (N) (m)

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How much work is done by a person who pulls a cart with a force of 50 newtons if the cart moves 20

meters in the direction of the force?

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The origin of energy in the universe is unknown.

• Most Scientists think it was created

during the big bang.

Scientists believe that the total amount of energy and matter in the universe is constant. *What does this mean?*

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This law states that energy can be neither created nor destroyed. It can

only be transformed from one type into one or more other types of energy (heat

may be released).

Electrical Energy

Mechanical Energy (Sound)

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1) Mechanical Spinning Fan

2) Chemical Burning Candle

3) Nuclear Nuclear Reactor

4) Heat Toaster

5) Electrical Generator

6) Light Lamp (bulb)

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Question: Where Does Candle Wax Go?

Answer: Have you ever noticed how you have less candle after burning than before? This is because the wax oxidizes (burns) in the flame to yield water and carbon dioxide, which dissipate in the air around the candle, in a reaction which also yields light and heat. Jennifer C. Brown

Based on what we know about energy, machines allow us to do incredible things.

A machine is a device with moving parts that work together to accomplish a task.

Initially, we invented simple machines like levers to

accomplish tasks.Jennifer C. Brown

Mechanical energy is the energy with which moving objects perform work.• Hammer striking a nail• Jack lifting a car• Pedals turning wheels of bicycle• Sound• You striking a match

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Sound Energy:• Sound is a form of energy produced by a

vibrating object. • When an object vibrates, it moves rapidly

back and forth, moving (expanding & compressing) the air around it and forming sound waves.

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• The substance that sound travels through is called the medium.

• Can sound waves travel through a vacuum? No, because there are no particles to transmit it.

• Similar to light, in what form do you think sound travels in? Waves

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Important Parts of a Wave:

• Wavelength – the distance from one point in a wave to a corresponding point in the next wave.

• Amplitude – the height of the crest measured from the undisturbed surface.

• Frequency – the number of waves that pass by a fixed point in a given amount of time.

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2 Main types of waves:• Transverse Wave – vibrates up and down at

a right angle to the direction in which the wave is traveling. ( shown by a rope moving up and down).

• Longitudinal Wave – vibrates back and forth within its direction of travel.

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Chemical energy is the energy stored in certain substances because of their chemical makeup. (ex. = batteries, foods, propane gas)

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The energy stored within the nucleus of an atom. This energy can be released by joining atoms together or by splitting atoms apart.

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The energy produced by the molecular motion of matter. (ex. – rubbing hands together, burning a match..)

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Produced by the flow of electrons through a conductor, such as a wire. (ex. – computers, televisions …)

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A form of radiant energy that moves in waves. (ex. – magnifying light, laser eye surgery…)

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Potential Energy:• The stored energy

of an object as a result of its position.

Kinetic Energy:

• The energy of motion (vertical or horizontal) Jennifer C. Brown

Equations:Equations:• Potential Energy

(in Joules)

EEpp = m = m xx g g xx h h

mass (m) mass (m) xx gravity (g) gravity (g) x x height (h)height (h)Jennifer C. Brown

• Kinetic Energy (in Joules)

EEkk = ½mv= ½mv22

mass (m) mass (m) xx velocity (v) velocity (v)Jennifer C. Brown

The speed of sound depends primarily on what 2 factors?

• The medium through which it is passing Denser medium = faster speed of sound

• The temperature Colder temperature = faster speed of sound

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Number the mediums from fastest speed of sound to lowest speed of sound:

Medium State

Iron Solid

Water Liquid

Air Gas

Glass Solid

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Light is a visible form of energy.Light is a visible form of energy.• Travels in waves• Travels in straight paths called rays• Unlike sound waves, however, light rays cannot

bend around objects.• When light strikes a surface:

Reflected Absorbed Transmitted

The smoother the surface, the more The smoother the surface, the more accurate the reflection. (mirror)accurate the reflection. (mirror)Jennifer C. Brown

Transparent Materials:Transparent Materials:• Ex – window glass• Permit almost all of the incoming light to pass through.

Translucent Materials:Translucent Materials:• Ex – wax paper• Let some light pass through but scatter the light so it isn’t

clear.

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RefractionRefraction• When light waves are

bent when passing through two media of different densities, such as from water into air.

• This is how a lens is made.

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A LensA Lens• A piece of transparent glass or plastic that has

curved surfaces. Convex Lens – (surface curves outward) Bends light rays

so they are focused in toward a common point. Concave Lens – (surface curves inward) Bends light rays

so they spread out.

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The Electromagnetic SpectrumThe Electromagnetic Spectrum• Light waves are a part of a larger group of

energy waves that can travel through a vacuum called electromagnetic waves.

• Electromagnetic Waves: Radio waves Microwaves Infrared waves Visible light Ultraviolet rays X rays Gamma rays

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