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All about EnergyEnergy – the ability to do work.

Work – what is accomplished when a force was put on an object and that object was moved.

Force – a push or pull that requires energy. What force are we familiar with? ________________

There are two major classes of energy:1. Potential Energy2. Kinetic Energy

Potential Energy - The energy of position or stored energy.Objects that are resting have high potential energy. Objects that are cooler have high potential energy.Kinetic Energy – The energy of motion. Objects that are moving have a high kinetic energy. High temperature objects also have a high kinetic energy.

Potential and Kinetic Energies are inverse.

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Electromagnetic Energy – energy that travels in the form of a wave

The Sun gives off Electromagnetic Energy

The Electromagnetic Spectrum is on page 14 in the ESRT’s… Go there

Waves from the spectrum travel as a transverse wave

A transverse wave is a wave that vibrates at right angles to it’s direction of travel (It goes up and down at the same time that it goes forward).

Crest – the tops of wavesTroughs – the bottoms of wavesAmplitude – the highest points of a wavesWavelength – the distance between two adjacent crestsFrequency - the # of crests passing a given point per second

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All objects give off electromagnetic energy. Even objects that are frozen give off EME. An object must be at ABSOLUTE ZERO(that is O K – all motion stops) in order for it to stop radiating energy. This temperature has not been reached as of yet.

Let’s get out page 14 in the ESRT’s and compare the two charts.

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A few facts:1. The Sun produces (radiates) mostly visible light2. The Earth gives off (re-radiates) mostly infrared (heat) at night3. Red light has the longest wavelength4. Blue-Violet light has the shortest wavelength5. Gamma rays have the shortest wavelengths of the electromagnetic spectrum6. Radio waves have the longest wavelengths of the entire spectrum7. Short waves are the most dangerous because there are more crests passing by8. Long waves are the safest because there are less crests passing by

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Short wave (visible light) is radiated by the Sun, and taken in by the Earth. Long wave (infrared) is re-radiated by the Earth at night.

The Sun produces more visible light than any other wavelength.

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When visible light hits the ground 4 different things can happen to it:

1. Reflected 2. Refracted 3. Scattered 4. Absorbed

Reflected – light is bounced back in the same direction from which it came

Refracted – light is bent as it passes through something

Scattered – the energy is bounced back in many directions

Absorbed – the light is taken in by the object that the light hits (the temperature will rise)

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INcoming SOLar radiATION Incoming Solar Radiation=

Sunlight

Reflection – lights reflects when it hits light colored, smooth, opaque surfaces (mirror, still water, …..)

Refraction - lights refracts when it hits light colored, smooth, transparent surfaces (sunrises/sunsets, objects appear bent in water)

Scattering – light scatters when it hits light colored, rough, opaque surfaces

Absorbed – light is absorbed when it hits dark colored, rough, opaque surfaces (blacktop gets hotter than grass, you don’t wear black cloths in the Sun)

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Energy TransferEnergy can neither be created nor destroyed. It can only be transferred from one form to another.

1. Conduction 2. Convection 3. Radiation

There are 3 ways to transfer energy:

The transfer of energy by the physical contact of atoms. Only SOLIDS transfer by conduction.

The transfer of energy through circulating fluids.Fluids can be either liquids or gases.

The transfer of energy by electromagnetic waves. This can happen in outer space (empty space) or in non-circulating air. The Sun gives us energy by radiation.

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Energy is transferred from a source to a sink. A source is an object that gives off more heat than it takes in.

A sink is an object that takes in more heat than it gives off.

Any object that is a good absorber of energy is also a good radiator of energy.

Energy is always transferred at an interface. An interface is a boundary!!!!! Remember that word

When two objects reach the same temperature they are at Dynamic Equilibrium (equal temperature).

Temperature – the average kinetic energy of the molecules (Measured with a thermometer and expressed in degrees)

Heat – the total kinetic energy of the molecules (Measured with a calorimeter and expressed in calories)

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Specific Heat A measure of how quickly or slowly a substance changes temperature

Objects with a high specific heat take a very long time to heat up or cool off. Liquid water changes temperature the slowest of all Earth materials.

Objects with a low specific heat will heat up and cool off very quickly. Metals heat up and cool off very quickly because they have a low specific heat. Lead has the lowest specific heat of all common Earth materials.

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Latent HeatThe energy needed for a substance to change phase without changing temperature.

There are 3 phases of matter: 1. Solid 2. Liquid 3. Gas (Vapor)

Molecules are closest together (Highest Density)

Molecules are spaced a bit further apart

Molecules are spaced the furthest apart

(Lowest Temperature) (Highest Temperature)Remember…water is the opposite to all other Earth materials. Water is actually the most dense as a liquid (ice floats in liquid water).

(Lowest Density)

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Phase Changes/State ChangesSolid to Liquid = Melting = Fusion - Heat is being addedLiquid to Vapor = Boiling = Evaporation – Vaporization – Heat is being added

Solid to Vapor = Sublimation – Heat is being added

Vapor to Liquid = Condensation – Heat is being removedLiquid to Solid = Freezing = Fusion – Heat is being removedVapor to Solid = Sublimation – Heat is being removed (How snow

forms)

Vapors have the most stored energy because they went through two phase changes (additions of heat) in order to become a vapor. So, vapors have the most Potential Energy, and solids have the least.

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1. The temperature does not change while a substance is changing phase.2. Latent Heat (stored/potential) is used during a phase change.3. Notice how there is a plateau during each phase change.4. Notice how the temperature increases between phase changes only.5. Other liquids (not water) have the same heat curve, but they plateau

(change phase) at different temperatures.