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Mahopac Central School
District Curriculum 2003-04
Energy
A. The atmosphere is the key player in the phenomena of global warming, ozone
depletion, and acid precipitation
1. The atmosphere is the shell of gases that surrounds the Earth
a. it is 78% nitrogen, 21% oxygen, 1 to 3% water vapor, .03% carbon dioxide
and .17% other gases
b. almost all (99%) of the atmosphere is within 30 Km/20 Mi of the surface
c. nearly all weather takes place in the troposphere, the lowest layer of the
atmosphere
1) the troposphere extends from the surface to about 10 Km above the
surface
B. The Earth’s primary source of energy is electromagnetic/radiant energy from the Sun
1. This energy is produced by a fusion reaction in the Sun
2. The complete series of electromagnetic energy is called the electromagnetic
spectrum
a. this spectrum includes visible light as well as six types of “light” not visible to
the human eye
3. All forms of electromagnetic energy travel through space in a form called a
transverse wave
a. these waves more at right angles (perpendicularly) to their direction of motion
b. they move at the speed of light (300,000Km/sec) in a vacuum
c. the primary difference between these types of “light” is their wavelength
1) wavelength is the distance between two adjacent crests – crests being
the high points on the wave form
2) the shorter the wavelength, the more energy the light wave has
d. radio waves have a wavelength measured in hundreds of kilometers while Xrays have a wavelength measured in billionths of a meter
4. Gamma rays and X-rays are very high energy forms of radiant energy –
exposure to these forms can be harmful to living organisms
5. Ultraviolet rays can tan or even burn the skin
a. it’s the ozone layer that limits our exposure to these UV rays
6. Visible light makes up a very small portion of the electromagnetic spectrum
a. visible light includes all the colors of the rainbow
7. Infrared rays can be felt (not seen) as heat
8. Microwaves and radio waves have the longest wavelengths on the
electromagnetic spectrum
C. Energy of any type can be transferred (moved from place to place) – there are three
ways to do this:
1. Radiation – electromagnetic waves (radiant energy) travels from the source to
the receiver
a. Sunlight to the Earth is a good example of radiation
b. Infrared rays (heat) traveling from a radiator to your hands is an example of
radiation, too
2. Convection – the transfer of heat energy in circulating fluids
a. this can only occur when there are density differences in the fluid
b. density currents form when cooler, higher density fluids sink and displace low
density, warmer fluids
c. this constant circling of the warm and cooler fluids forms a convection cell
Mahopac Central School
District Curriculum 2003-04
d. air in a classroom is circulated by convection cells
3. Conduction – the transfer of heat energy by colliding particles
a. this occurs in solids because the particles of matter are packed most closely
together
b. most metals conduct heat energy well
D. Weather is the temperature, cloud cover, precipitation, wind speed, and humidity at
any particular location
1. The Sun is the main source of energy in the atmosphere
2. The uneven distribution of heat energy in the atmosphere is the cause of weather
a. this uneven distribution of energy in the atmosphere results in huge
convection cells
b. add to this the air brought to a region by prevailing and local winds and you
can see that the properties of air (weather) is constantly changing
3. The heating of the Earth’s surface depends to some extent on the characteristics
of the surface
a. simply put, some types of surfaces get hotter than others
4. It also depends on the angle at which sunlight strikes the surface
a. near the equator the sun’s rays strike the surface vertically, or nearly so
b. this concentrates the energy within a small area heating it very efficiently
c. the farther from the equator you get, the more slanted the sun’s rays become,
and the less efficiently the surface is heated
E. Weather Variables
1. Air Temperature
a. it depends on: surface characteristics beneath the air, angle of sunlight,
duration of sunlight
2. Air Pressure – the weight the air overhead presses down with
a. it depends on air temperature and altitude
1) as temperature goes up, air becomes less dense, so weight and pressure
go down
2) as altitude goes up, there is less air overhead so weight and pressure go
down
3. Humidity – the amount of water vapor present in the air
a. relative humidity – the ratio between the actual amount of water vapor in the
air and the maximum amount of water vapor the air can hold
b. warmer air can hold more water vapor than cooler air
c. when air is cooled to the point that the vapor changes to a liquid, that’s called
the dewpoint temperature
4. Wind – the movement of air over the Earth’s surface
a. winds always move from areas of higher pressure to areas of lower pressure
b. winds are named for where they come from, not the direction they are going
c. sea breeze – land heats faster on a sunny day, temperatures rise, air
pressure falls, wind rushes in from over the cooler ocean
d. land breeze – land cools faster than water at night, temperatures fall, air
pressure rises, wind rushes out from land over the warmer ocean
5. Clouds – masses of tiny water droplets or ice crystals suspended in the air
a. cumulus – fluffy, “cotton ball” appearance – associated with fair weather
b. stratus – wall to wall gray skies – nimbostratus bring precipitation –
associated with the passage of a warm front
c. cirrus – wispy, high level clouds made of ice crystals – precede rainy weather
– also known as “horse tails”
Mahopac Central School
District Curriculum 2003-04
d. cumulonimbus – “thunderheads”- associated with the passage of a cold front
– also associated with violent weather
6. Precipitation – water in any form falling from the sky
a. rain, snow, sleet, hail
b. precipitation cleans the atmosphere
F. Air Masses – a large body of air that has uniform temperature and moisture
conditions throughout
1. Air masses form when air stays over a large area of the Earth’s surface and
takes on the characteristics of that surface
a. air masses that form over the Gulf of Mexico are warm and moist and are
called tropical maritime air masses
b. air masses that form over Canada are cool and dry and are called polar
continental air masses
c. polar=cool/cold, tropical=warm/hot, maritime=moist, continental=dry
2. There are two general types of air masses: high pressure centers and low
pressure centers
3. High Pressure Centers
a. air sinks in the center of a high
b. winds move outward from the center of a high turning clockwise as they do
c. highs usually bring clear skies, dry weather, and gentle winds
4. Low Pressure Centers
a. air rises in the center of a low
b. winds move inward towards the center of a low turning counterclockwise as
they do
c. lows usually bring cloudy skies, wet weather, and strong, gusty winds
G. Fronts – formed when two air masses meet – characterized by rapid weather
changes accompanied by precipitation
1. Cold Front – a cold air mass pushes into a warmer air mass
a. associated with thunderstorms and lightning in the summer months – the
precipitation is short and severe
b. the edge of the cold, dense air “wedges” underneath the warmer air and
pushes it up and out of the way
c. the water vapor in this rising warmer air condenses out and falls as
precipitation
d. on a weather map, the symbol is a line with triangles on one side
1) the triangles point in the direction the front is moving
2. Warm Front – a warm air mass glides up and over the back of a slower moving,
colder air mass
a. feathery cirrus clouds form first, followed by stratus clouds later
b. associated with widespread gentle precipitation – slow and steady rain
c. on a weather map, the symbol is a line with semicircles on one side
1) the semicircles point in the direction the front is moving
3. Occluded Front – a fast moving cold air mass overtakes and lifts a warmer air
mass trapping the warmer air above
a. large scale precipitation is associated with an occluded front
b. on a weather map, the symbol is a line with alternating triangles and
semicircles on one side
1) the triangles and semicircles point in the direction the front is moving
4. Stationary Front – two different air masses meet, but move very slowly or not at
all
Mahopac Central School
District Curriculum 2003-04
a. these can sit over a region for days until a new air mass moves in with
enough force to push the stalled air masses out of the way
b. on a weather map, the symbol is a line with triangles on one side and
semicircles on the other side
H. Weather Forecasting
1. Weather maps show temperatures, air pressures, wind speeds, and relative
humidities
2. A synoptic weather map is a summary created from data collected from
numerous weather stations
a. this information can be used to create field maps
b. a field map is created by connecting points of equal value with lines called
isolines
1) if the points connected are air temperature, the lines are called isotherms
2) if the points connected are air pressure, the lines are called isobars
3. It is the movement of air masses and fronts that allows meteorologists to make
weather predictions
a. in the United States, weather tends to move from the southwest to the
northeast under the influence of the jet streams and prevailing
southwesterlies
4. Weather Forecasting Clues:
a. falling air pressure signals the approach of a storm, rising air pressure signals
fair weather is coming
b. increasing cloudiness signals a front is approaching
c. in New York State, winds from the west bring fair weather, winds from the
south or the east bring wet weather
I. Hazardous Weather Conditions
1. Thunderstorms
a. form after severe heating of the Earth’s surface
b. form with the passage of a cold front – a really strong cold front produces a
squall line
c. hazards include: lightning, heavy rains, high winds, and flooding
2. Tornadoes – funnel shaped, rapidly rotating columns of clouds and air
a. usually form late in the day and are associated with severe thunderstorms
and cold fronts
b. wind speeds up to 500 Km/Hr (300+Mi/Hr) cause extreme damage to
property
c. hazards include: collapsing structures and flying debris
3. Hurricanes – large tropical cyclones (low pressure centers)
a. they usually occur from September to November
b. hazards include: high winds, flying debris, storm surge (flooding)
4. Blizzards – winter storms with high winds and frozen precipitation
a. hazards include: damage to homes, trees, and infrastructure, hypothermia
5. Ice Storms
a. occur when temperatures in the upper atmosphere are warmer than the lower
atmosphere
b. liquid precipitation lands on cold surfaces and freezes solid
c. hazards include: traffic accidents, falling debris from homes and trees, falling
power lines
J. Water Cycle – it’s powered by the Sun’s energy
Mahopac Central School
District Curriculum 2003-04
1. Liquid water evaporates into the atmosphere (mostly from the oceans) and
plants release water vapor directly into the air
2. Rising air cools, cooler air can’t hold all the water vapor, so some begins to
condense
3. Dew, fog, and clouds form from condensation of water vapor
a. dew is what’s formed when water vapor condenses on a cool surface
b. fog is formed when tiny liquid water droplets are suspended in the air at
ground level
c. clouds are just a collection of tiny liquid water droplets or ice crystals
suspended in the atmosphere
4. If smaller droplets combine they can fall to the surface as precipitation
5. Runoff (streams and rivers) carry the water back to the oceans
6. This cycle of evaporation, condensation, precipitation, and runoff can then start
again
K. Climate – the weather conditions in an area over a long period of time – a number of
factors combine to influence climate
1. Latitude – places far from the equator have colder climates, near the equator
warmer climates, and mid-latitude locations have seasonal variations in
conditions
2. Altitude – higher elevations have colder climates than lower elevations
3. Large Bodies of Water
a. being close to a large body of water produces a moderate climate – cooler
summers and warmer winters than expected for the latitude and altitude
b. this is because water absorbs and releases heat very slowly over time
4. Mountain Barriers
a. the side facing the prevailing winds tend to have cooler, moist climates
b. the opposite side has a warmer, drier climate
___________________________________________________ END Energy 1
Mahopac Central School
District Curriculum 2003-04
L. Waves
1. Most of the Sun’s energy arrives at the Earth by the radiation of transverse
waves across the vacuum of outer space
2. However, energy can also travel in the form of vibrational waves
a. these vibrational waves are also known as compressional or longitudinal
waves
3. As these waves travel through matter, particles in the matter compress together
and then spread apart
a. sound waves are an example of this wave type
b. these waves move faster at higher temperatures and faster through materials
of higher density
c. sound waves travel much slower than light waves under most conditions
4. When earthquakes occur, both kinds of waves are produced
a. primary earthquake waves are compressional/longitudinal
b. secondary earthquake waves are transverse
M. The energy in waves interacts with matter in different ways
1. It can be transmitted – it passes through the matter
2. It can be absorbed – it is taken into the matter usually making the temperature of
the matter rise
3. It can be reflected – it bounces off the matter
a. white surfaces reflect all visible wavelengths
b. black surfaces absorb all visible wavelength
c. a color is just one particular wavelength being reflected back to your eye
d. smooth, shiny surfaces reflect well. rough, dark surfaces absorb well
4. It can be diffracted – it is bent around barriers – like sunlight at dawn or dusk
5. It can be refracted – it is bent out of its normal path as it passes through the
substance
N. Energy – it’s what allows work to be done (or changes to occur)
1. Chemical energy – results when chemical bonds are broken – TNT
2. Heat energy – the energy transferred from a warmer to a cooler object
3. Radiant energy – the energy that travels in the form of transverse waves
4. Sound energy – the energy that travels in the form of longitudinal/vibrational
waves
5. Mechanical energy – the energy associated with the motion of matter
6. Nuclear energy – the energy produced from the inside of an atom
a. fission – the heavy nucleus of Uranium splits into two smaller nuclei with the
release of heat energy
1) nuclear power plants use fission to boil water to produce steam to power
turbines that generate electricity
2) the disposal of nuclear waste is the biggest problem with fission reactors
b. fusion – hydrogen nuclei join together (fuse) to form helium nuclei with the
release of types of radiant energy
1) the Sun and other stars are powered by fusion reactions
7. Solar energy – energy from the Sun
8. Electrical energy – energy produced by the flow of electrons through a conductor
a. static electricity occurs when there is a build-up of charges on matter (number
of protons does not equal the number of electrons)
1) lightning is a static electric discharge
b. in order for electricity to do work, it needs to travel through a conductor
1) metals make excellent conductors
Mahopac Central School
District Curriculum 2003-04
c. the Law of Charges states: “like charges repel while unlike charges attract” –
just like the Law of Poles for magnets
d. all electrical devices use current (vs static) electricity – a flow of electrical
charges
e. a circuit provides a complete closed path for electricity to follow from a
negative to a positive connection
f. a circuit contains loads (devices that use electricity) that can open or close
the circuit (like a switch does)
g. in a series circuit, electricity must travel through all its loads before it travels
back to its source
1) if one load fails, the whole circuit is broken
h. in a parallel circuit, each load has its own path back to the source of
electricity
1) if one load fails, the others work just fine
i. current electricity gives rise to a magnetic field
1) when wire is coiled and electricity flows through the coil, a magnetic field
is generated
2) it works better if the wire is coiled around a rod of soft iron
3) these coils are called electromagnets
The Law of Conservation of Energy – energy can be neither created nor destroyed but it
can be transferred (moved from place to place) or transformed (changed into another
type)
a. no energy transfer can take place with 100% efficiency
b. there is no way to move energy from place to place without having some
escape into the surrounding environment
9. Renewable and Nonrenewable Energies
a. nonrenewable resources are those that can be used up and can’t be replaced
1) fossil fuels (oil, coal. Natural gas) are nonrenewable
b. renewable resources can be used without worry about running out of them or
using them up
1) sunlight, wind, falling water, tides, geothermal, and biomass are
renewable
O. Kinetic and Potential Energies
1. Potential energy is stored energy and is determined by an objects position
a. the height and weight of an object influences how much potential energy it
has
b. the greater the weight, the greater the gravitational potential energy and the
greater the height from which an object falls, the greater the gravitational
potential energy
2. Kinetic energy is energy of motion
a. it is determined by velocity and mass
b. the greater the velocity of an object, the greater the amount of kinetic energy
it has
c. if two objects are traveling at the same velocity, the one with the greater
mass has the greater kinetic energy
3. Temperature is a measure of the average kinetic energy of molecules – a
measure of molecular motion
a. temperature in measured in degrees
Mahopac Central School
District Curriculum 2003-04
4. Heat is the energy transferred (moved) from a hotter to a cooler object
a. heat is measured in calories
b. the amount of heat energy moved depends on:
1) mass
2) the change in temperature of the object receiving or releasing the energy
3) the specific heat of the substance (a measure of how quickly the
substance can change temperature)
P. Phase Changes and Energy
1. A phase change is when matter changes from one form to another form
2. Heat energy is either absorbed or released during a phase change
a. melting – a change from a solid to a liquid – energy is absorbed – the
molecules of matter spread out and move faster
1) melting occurs at the freezing point (melting point = freezing point)
2) freezing point is the temperature at which the substance changes phase
from a liquid to a solid
b. vaporization – a change from a liquid to a vapor – energy is absorbed – the
molecules of matter spread out even more and move even faster
1) vaporization occurs at the boiling point
2) boiling point is the temperature at which the substance changes phase
from a liquid to a vapor
c. sublimation – a change from a solid directly to a vapor – energy is absorbed
d. deposition – a change from a vapor directly to a solid – energy is released
e. condensation – a change from a vapor to a liquid – energy is released – the
molecules of matter move closer together and slow down
f. freezing – a change from a liquid to a solid – energy is released – the
molecules of matter move even closer together and slow down even more
g. evaporation – similar to vaporization (liquid to vapor) except that it happens at
the surface of a liquid at temperatures lower than the boiling point
Q. Change of Phase Graphs (use with a change of phase diagram)
1. As long as a substance remains in one phase, as heat energy is added,
temperature increases
2. When a substance changes phase, temperatures remain the same (a plateau
appears on the graph)
a. this is because the heat energy added/released is being used to help the
substance change form rather than change the rate at which the molecules
move
3. The longer the plateau, the more energy is involved
4. The steeper the sloped line, the greater the rate of temperature change
5. When read from left to right, energy is required to change the phase
6. When read from right to left, energy is released during the change in phase
_____________________________________________ END Energy 2