Energy Processes in Earth Science

Earth Science

Mr. Clark

Bethpage High School

Energy

• Energy

• Transfer of Energy

• Conduction

• Convection

• Radiation

• Electromagnetic Energy’s Interactions with Matter

Energy

• Terrestrial Radiation

• The Greenhouse Effect

• First Law of Thermodynamics

• Second Law of Thermodynamics

• Kinetic energy

• Potential energy

• Heat and Temperature

Energy

• Energy is the ability to do work.

• Energy is measured in units called Joules.

• Energy is also measured in calories.

Transfer of Energy

Energy can be transferred in three ways:Conduction Conduction ConvectionConvectionRadiationRadiation

Transfer of Energy

• Conduction is the transfer of heat energy through molecular collisions.

• Convection is the transfer of heat energy through currents formed due to density differences.

• Radiation is the transfer of electromagnetic energy through space. Radiation requires no medium. (matter)

Conduction

• Conduction can occur with solids, liquids, or gases.

• Contact must be made to conduct heat.

Convection

• Convection is due to density differences, it creates currents.

• Convection is the driving force behind global winds, ocean currents, and plate tectonics.

• A convection box can be used to show convection.

Radiation

• Electromagnetic radiation radiates through space.

• Electromagnetic radiation travels at the speed of light.

• Light is part of the visible spectrum of the electromagnetic spectrum.

Electromagnetic Spectrum

Radiation

• Electromagnetic radiation has both wave properties and particle properties.

• We describe light in a term called a photon.

• Electromagnetic waves are a type of wave called a transverse wave.

Waves

Waves

• Wavelength (distance between two successive crests)

• Crest (high point of wave)

• Trough (low point of wave)

Waves

• Amplitude (height of the wave in the center of the crest)

• Frequency (how often a wave passes per unit time)

• Wave Velocity (the speed and direction of the wave)

Electromagnetic Energy’s Interactions with Matter

• Reflection (bounces off)

• Refraction (bends)

• Absorption (taken in)

• Scattering (bounces and bends)

• Transmission (passes through)

Insolation

• Insolation (incoming solar radiation) can be absorbed by the Earth.

• Absorption by Earth materials– Color and texture affect absorption.– Dark colors and rough surfaces absorb the

best.

Terrestrial Radiation

• Terrestrial radiation is the radiation given off by the Earth when it heats up after absorbing insolation.

• When energy is absorbed it is always reradiated at a longer wavelength because longer wavelengths contain less energy.

Terrestrial Radiation

• Earth materials absorb shorter wavelength visible light and emit longer wavelength infrared radiation.

• Infrared radiation (IR) is heat energy.

Radiation rule

• Rule: A good absorber is a good radiator.

Terrestrial Radiation

• Specific Heat: The lower the specific heat the better the absorption.

• Granite and Basalt have low specific heats and therefore heat up quickly and cool down quickly.

• Water has the highest specific heat of Earth materials so it is the poorest absorber and therefore heats up and cools down the slowest.

The Greenhouse Effect

• Certain materials (glass) allow the shorter wavelength (visible light) to pass through them (transparent) but do not allow longer wavelengths (infrared) to pass through (opaque) and therefore trap longer wavelength (infrared) radiation and cause the temperatures inside the glass to rise.

The Greenhouse Effect

• Certain gases in the Earth’s atmosphere are greenhouse gases, among them are carbon dioxide, methane, and water vapor.

• If concentrations of these gases get too high, global warming could ensue.

• Global Warming would have drastic effects upon the Earth's climate.

• The planet Venus has these conditions.

First Law of ThermodynamicsConservation of Energy

• Energy is neither created nor destroyed but is always conserved and transformed from one kind to another.

• Energy only changes form.

• You cannot get something from nothing.

• Energy in = energy out

Second Law of Thermodynamics

• Energy always goes from a more usable form (high quality) to a less usable form (low quality).

• Heat always travels from hot to cold.

• All systems proceed to maximum entropy (randomness).

Kinetic Energy

• Kinetic energy is the energy of motion.

• KE = ½ mv2 where m is mass and v is velocity.

Potential Energy

• Potential energy is stored energy.

• PE = m x g x h where m is mass, g is the acceleration due to gravity, and h is height.

Heat and Temperature

• They are not the same.

• Temperature is average kinetic energy of the molecules in a sample of matter.

• Heat is the total internal energy of a sample of matter.

Temperature

• There are three temperature scales:

• Fahrenheit

• Celsius

• Kelvin

• To convert use the Earth Science Reference Tables or use a formula.

Temperature Scales

Heat

• Heat is a measure of total internal energy.

• Heat is measured in calories.

• Q = m cp DT

• Where Q is heat energy in joules, m is mass cp is specific heat, and DT is the

change in Temperature.

Specific Heats

Sample Heat Problem

• How many calories are absorbed when 50.0 g of water are heated from 30o C to 60o C?

• Solution:

• Q = m cp DT

• Q = (50.0 g) (4.18 J/g oC)(30 oC)

• Q = 6270 J or 6.270 kcal

Changes of Phase

• Solid to liquid = melting

• Liquid to solid = solidification

• Liquid to gas = vaporization (evaporation)

• Gas to liquid = condensation

• Solid to gas = sublimation

• There is no change in temperature during a phase change. Only latent heat may be added or released.

Latent Heat of Fusion

• The heat needed to convert a mass from solid to liquid is the latent heat of fusion.

• Heat of fusion for water is 334 J/g. (ESRT)

Latent Heat of Fusion Problem

• Sample problem:• How many calories are required to melt

a 255g ice cube at 0 oC?• Q = mass X heat of fusion• Q = (255g) (334 J/g) = 85170 J

Latent Heat of Vaporization

• The heat needed to convert a mass from a liquid to a gas is the latent heat of vaporization.

• Heat of vaporization for water is 2260 J/g. (ESRT)

Latent Heat of vaporization Problem

• Sample problem

• How many calories are required to vaporize a 423g of water at 100 oC and 1 atmosphere of pressure?

• Q = mass X heat of vaporization

• Q = (423g) (2260 J/g) = 955980 J

Heating Curve of Water

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temperature

Heating Curve of Water

• The heating of a solid results in a liquid. • The heating of a liquid results in a gas.• The flat part of the curve represents a

phase change.• Phase changes during are not

accompanied by temperature changes.• Reading the curve in reverse is a

cooling curve.