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Matter & Energy General Concepts
1) Physical Science is a very large branch of science that deals with the study of matter and energy. It
includes both Physics and Chemistry. Physics is the study of how objects in the universe move and how
they use energy to interact with each other. Chemistry is the study of what objects in the universe are made
of. The word chemistry comes from the Latin word “Alchemista” or alchemy. It deals with particles and
how they combine to form substances.
2) The two most basic substances in the entire universe are matter and energy. Matter is stuff that takes up
space, has volume and mass, and does not move by itself. It needs energy to move. Volume (v) refers to
the size of an object. It is measured in liters (l). The mass (m) of an object refers to the amount of matter it
has. Mass could be measured by counting the particles of an object. But since this not practical, it is
measured by the object’s inertia (resistance to changing motion – Newton’s first law of motion) or how hard
it is to push. Mass is not the same thing as weight because mass is constant and weight is not. Mass is
measured in grams or kilograms (kg). Weight (w) is the force or pull due to gravity. The force of gravity
may change depending on position, so weight may also change. Weight (w) is measured in Newtons (N).
3) Atoms are made of electrons, protons, and neutrons. All matter is made of a combination of these
particles. Normally, atoms have equal numbers of protons, neutrons, and electrons. A charged particle is a
particle of matter and a particle of energy fused together. Protons have a positive charge (+), electrons
have a negative charge (-), while neutrons are neutral – no charge. Particles with the same sign attract,
while those with opposite signs repel.
4) Every atom has a center or nucleus where the protons
and neutrons are bonded together. Electrons are what
make chemical reactions and are what bonds one atom to
another atom to make molecules. The electrons move at
specific distances around the nucleus called energy levels
or shells. The closest or inner shell can hold a maximum
of two electrons. The second shell can hold a max of 8
electrons. The third shell can hold a max of 18 electrons. The fourth shell can hold a max of 32 electrons.
5) Since electrons are attracted to the nucleus, an atom's electrons will fill inner shells completely first
before filling outer shells. For example, an atom with 8 protons (oxygen) will also have 8 neutrons and 8
electrons. The electrons will be placed in the following locations: 2 in the first shell and 6 in the second
shell. Another example: an atom with 20 protons (calcium) will also have 20 neutrons and 20 electrons.
The electrons will be placed in the following locations: 2 in the first shell, 8 in the second shell, and 10 in
the outer third shell. The electrons in the outermost occupied shell determine the chemical properties of the
atom and how it sticks to other atoms. It is called the valence shell.
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6) The only difference between one atom and another is the number of protons in its nucleus. Each atom is
called an element, and is given an atomic number that relates to its number of protons. The atomic mass
of an element is the number of protons plus neutrons. It is usually 2 to 2.5 times the atomic number.
7) Properties of an element are classed as either chemical or physical. Physical properties such as
temperature, magnetism, volume, mass, and density are observed by examining a sample of the pure
element. A physical change is when a substance changes its form or shape but does not create a new
substance.
8) Chemical properties of an element such as conductivity, reactivity, acidity, and flammability are due to
the location of electrons around the atom's nucleus, particularly the outer electrons, or valence electrons.
Chemical properties are usually observed with a chemical reaction or chemical change where elements are
combined to form a new substance. A chemical reaction does not affect the nucleus. So the atomic number
of each atom does not change in a chemical reaction.
9) A compound is a substance made from two or more elements chemically bonded to form a unique
substance. It is a chemical change. A mixture is a combination of two or more substances that are not
chemically combined and can be readily separated without breaking atomic bonds. It is a physical change.
10) Stable elements are atoms that do not readily change, react, or stick to other atoms. Atoms are stable
when (1) they have the same number of protons, neutrons, and electrons, and (2) their outer electron shell is
filled. Only the Noble Gas family of atoms (helium, neon, argon, krypton, radon, and xenon) meets both of
these. These atoms do not stick to anything. If an atom or mixture is said to be inert, it does not undergo
chemical reactions.
11) Reactive elements are atoms that try to change or combine with other elements. An ion is a reactive
atom with more or fewer electrons than protons. A positive ion or cation (+) means fewer electrons than
protons. A negative ion or anion (-) means more electrons than protons. Isotopes are reactive atoms with
more or less neutrons than protons. Most isotopes are radioactive – particles spit out of the nucleus.
12) Elements can also be also reactive because of their electron location. When the outer shells of atoms are
not filled to max, they try to take electrons from other atoms. This is what makes atoms stick together.
Rust (iron) or corrosion (all other metals) is an example of a reactive element or molecule (such as water,
air, acids) whose outer electron shell is not filled. It takes electrons from other molecules breaking their
bonds in order to fill its own outer shell.
13) The pH scale (power of hydrogen) measures the concentration of acids (hydrogen ions H+) and the
concentration of bases (hydroxyl ions OH-) in a solution. A solution is where something is evenly
dissolved. Acids and bases must be in a liquid form. Pure water (H2O) has a pH of 7 and is neutral. Pure
water is neither an acid or a base. Acidic solutions have a low pH of 0 to >7, while basic solutions have a
high pH of <7 to 14. Basic solutions are also called alkaline.
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14) The pH scale is a logarithm scale which means each number is 10 times greater than the next number.
For example, lemon juice which has a pH of 2 is ten times more acidic than vinegar which has a pH of 3,
100 times more acidic than tomato juice which has a pH of 4, and 1000 times more acidic than black coffee
which has a pH of 5.
15) Acids steal electrons from molecules breaking their bonds. They taste sour and are identified by a red
color on blue litmus paper. Bases give electrons away breaking molecular bonds. They taste bitter, feel
slippery, and are identified by the color blue on red litmus paper. Both acids and bases conduct electricity
and change the color of other molecules. When mixed, they trade electrons, may neutralize if the
concentrations are equal, and form salt plus water. When something dissolves, molecules are broken apart
from other molecules.
16) A buffer is a solution that resists change in pH. If you add an acid, base, or water to a buffered
solution, its pH will not change much. Many life forms thrive only in a relatively small pH range so they
use a buffer solution to maintain a constant pH. One example of a buffer solution found in nature is blood.
17) The elements are grouped according to their chemical and physical properties. One major classification
is as metals, nonmetals, and metalloids. There are more metals than any other type of element, but
nonmetals make up all life as we know it.
18) Metals are good conductors of both electricity and heat. They are usually shiny, have high melting
points, are solids at room temperature, and are malleable (able to be hammered or pressed permanently out
of shape without breaking or cracking) and ductile (able to be pulled or stretched into thin wire without
breaking). An alloy is a physical combination of different metals that has properties of both.
19) If something is a good electrical conductor, it will allow electricity/electrons to pass through it without
melting or catching on fire. If something is a good electrical insulator, it will block or slow down
electricity. If something is a good thermal conductor, it will allow heat to pass through it without melting
or catching on fire. If something is a good thermal insulator, it will block or slow down heat.
20) Most nonmetals are gasses at room temperature. In their solid state they are usually brittle (they break
rather than bend) and they are insulators of both heat and electricity. Wood and plastic are nonmetal
compounds that are insulators. Carbon is a nonmetal (atomic number 6) element that is found in every
living thing. A whole branch of science called Organic Chemistry studies how carbon works.
21) Metalloids are partly like metals and partly like nonmetals. Most are semiconductors, which means
that they conduct electricity under some conditions but not others. Silicon is a very useful metalloid.
22) Dmitri Mendeleev, a Russian chemist, is generally given credit for developing the first periodic table in
1869. The modern Periodic Table of Elements is a chart that lines up the known elements in order of
increasing atomic number and their electron locations.
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23) In the periodic table there are 7 horizontal rows called periods that align elements by their electron
shells. There are 18 vertical columns called groups or families that align elements by their outer electron
numbers and their similar chemical properties. Except for group 18, elements on the left side or right side
of the table tend to be more reactive (they chemically bond with more elements) than elements in the middle
which are more stable.
24) The Alkali Metal family (group 1, except for hydrogen) has elements that are very reactive and readily
form compounds but are not found free in nature. They form salts and alkali (acid-neutralizing) compounds
such as baking soda. In pure form, they are very soft metals which catch fire on contact with water. Some
examples are lithium, sodium, and potassium.
25) The Alkali Earth Metal family (group 2) has elements that are reactive and readily form compounds
but are not found free in nature. In pure form, they are soft and somewhat brittle metals. Some examples
are magnesium and calcium.
26) Transition Metals (groups 3 through 12) are typical metals. They are strong, shiny, malleable, flexible,
and they conduct both heat and electricity. Some examples are titanium, copper, iron, zinc, silver, and gold.
27) The Halogen family (group 17) has elements that are reactive nonmetals and readily form compounds,
but are not found free in nature. They combine with alkali metals to form salts. Halogen means salt-former.
Some examples are fluorine, chlorine, and iodine.
28) The Noble Gases family (group 18) has elements that are inactive, or inert. Each atom has exactly the
number of electrons it needs to have a full outer shell, so these atoms almost never bond with other atoms.
That is why these are all gases. Some examples are helium, neon, and radon.
29) Energy is the ability to do work or make things move. Because energy does not have mass or volume
(matter), it is described by the things that it does - its interaction with matter. It is measured in joules (J).
30) A force (f) is any push or pull. More scientifically, it is any influence, such as gravity, that can change
the motion of an object. Forces are measured in the metric system by a unit called a newton (N).
Scientifically, 1 newton equals a force that will give a 1 kilogram mass an acceleration (a) of 1 meter per
second per second (kg)(m)/(s2).
31) Work (W) is defined as force that acts over a distance, or the movement of an object from one location
or position to another. Work is measured using the metric unit joule (J). Work equals force times distance.
The equation for work is: W = f  d Distance (d) in the metric system is measured in meters (m). If a 500N
box is lifted 2 meters, 1000J of work has been done because 500N times 2m = 1000J
32) Each time work is done energy is transferred or given by one object to another that allows it to do work.
So work is also understood to be the transfer of energy. When a certain amount of work is done, the same
amount of energy is involved. Energy is therefore measured in joules just like work.
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33) Energy can either be used right away or stored for use later. All energy involves either motion or
position/shape/chemistry. All energy types and sources will be measured as either potential or kinetic.
34) Energy that is stored and is not being used is called potential energy (PE). Since these objects are not
moving and are resting, there is no work being done. Potential energy is still measured in joules because of
the object’s potential to do work. It is measured by its position or shape or chemistry. Weight is PE due to
its position. All food and fuel is PE due to its chemistry. A stretched spring is PE due to its shape. PE can
also be measured as weight times height. A 10 newton object 2 meters above the ground has a PE of 20J.
35) Kinetic energy (KE) is energy in motion that is being used. Work is being done. All moving objects
have kinetic energy and are doing work. The amount of kinetic energy of an object depends on its mass and
speed. The faster an object moves or the more massive it is, the more kinetic energy it has. Kinetic energy
is measured in joules (J) by multiplying the mass in kilograms by the velocity squared in meters per second,
and then and dividing by two. The equation is: KE = ½ mv2
36) All energy travels in waves - either through matter or by itself in the form of electromagnetic radiation.
An energy wave that travels through matter is called a mechanical wave. The material a wave travels
through is called a medium.
37) Mechanical waves form when a source of energy causes a medium to vibrate. A vibration is a
repeated back-and-forth or up-and-down motion. Although the particles of matter move as the energy
passes through it, the particles do not travel with the wave. There are three main types of mechanical waves
that are classified by the direction of movement of the particles: transverse, longitudinal, and surface.
38) A transverse wave vibrates the medium particles at right angles to its movement through the material.
S waves, also called secondary waves or shear
waves, are a type of seismic wave and are an
example of a transverse wave. A vibrating
string is another example of a transverse wave.
All points on the string itself are fixed to a point
and move only up and down, but the wave
pulses move at a right angle along the length of
the string. The wave speed is the speed with
which a pulse moves along the string.
Electromagnetic or radiant energy also travels
in transverse waves, only this form does not
need a medium.
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39) A longitudinal wave, sometimes called a compression wave or a push-pull wave, vibrates the medium
particles in the same direction as the movement of the wave. As the energy moves through, some particles
get close together called compression. At the same time some particles are spread out called rarefaction.
The compressions and rarefactions travel along the whole way with the wave, but the individual particles do
not move with the wave. After the wave passes, the particles return to their original position. P waves or
primary waves are a type of seismic wave and are an example of a longitudinal wave.
40) Sound energy (SE) is the vibration of
particles along a path. Energy is transmitted from
particle to particle forming a chain or compression
wave or longitudinal waves.
41) Surface waves are a combination of
transverse and longitudinal waves. This type of
wave travels along a surface that separates two
mediums. Ocean waves are the most familiar.
When a wave passes through water, the water
moves up-and-down and also back-and-forth. The
individual particles actually make a circular
motion as the wave passes by. Another type of
surface wave is the Rayleigh wave. These are
seismic waves that are the most easily felt during an earthquake. They cause the most damage.
42) Waves are measured by their wavelength, amplitude, frequency, and speed. Transverse waves have a
high point called a crest and low point called a trough. Amplitude measures how big the wave is or the
height of the wave from the crest to the trough. In sound, amplitude describes the loudness or amount of
energy.
Wavelength (λ) (the Greek letter lambda is the symbol for wavelength) is the distance between
individual waves or the distance between two crests or troughs of the wave. It is measured in meters (m).
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43) Frequency (f) is the number of waves that pass a point in a certain time period. Frequency is measured
in Hertz (Hz). One Hz is one wave per second (f = 1/t). As the frequency of the wave is increased, its
waves are closer together so the wavelength is smaller. As the frequency of the wave decreases, the waves
are farther apart so the wavelength increases. The sensation of a frequency is commonly referred to as the
pitch of a sound. A high pitch sound matches to a high frequency sound wave and a low pitch sound
matches to a low frequency sound wave. An average human ear is capable of detecting sound waves with a
wide range of frequencies, ranging between approximately 20 Hz to 20,000 Hz. Any sound with a
frequency lower than the normal hearing range (less than 20 Hz) is known as an infrasound, and any sound
with a frequency higher than the normal hearing range (more than 20,000 Hz) is known as an ultrasound.
44) The speed (v) of a wave depends on the density of the material that it is passing through. It is measured
in meters per second (m/s), or feet per second (ft/s), or miles per hour (mph). The closer the particles, the
faster the wave. The speed of sound: air at 68F = 1130 ft/s, 770 mph; water = 5000 ft/s, 3409 mph; steel
= 20,000 ft/s, 13,636 mph. The speed of light in space is about 186,000 miles per second. Air slows it
down a little, but its speed through water is much slower at 140,000 mi/s and 122,000 mi/s through glass.
45) Since frequency is measured by waves per second or 1/t and since velocity (speed in a certain direction)
is measured by distance divided by time or wavelength divided by period (r=d/t), we can calculate the
velocity of a wave as wavelength times frequency or v wave = λf For example: if a wave has a wavelength of
11 meters and a frequency of 10 Hz, its speed is 110 m/s. Note the unit is meters per second.
46) There are seven types of energy. They are mechanical, sound, chemical, nuclear, thermal, electrical,
and radiant. Thermal, electrical, and radiant are measured as only kinetic energy. Chemical and nuclear are
measured as only potential energy. Mechanical and sound are measured as both potential and kinetic.
47) Mechanical energy (ME) is the energy of moving objects. It may include either potential or kinetic
energy types, or it may include both at the same time. The mechanical energy of an object can be measured
by adding its potential and kinetic energies together. ME = PE + KE The amount of an object’s PE or KE
may change, but it mechanical energy must remain constant. When PE increases, KE must decrease, or
when PE decreases, KE must increase.
48) A pendulum clock is a compound machine that uses stored energy to do work. A spring stores energy,
and with each swing, some of the PE is converted to KE to move the hands. At the top of the swing PE is
greatest and KE = 0. At the bottom of the swing, KE is the greatest and PE = 0. At any time, the PE and
KE can be added to find the total energy of the system. The same concept applies with stretching materials
like springs and rubber bands. For example: in a pendulum if the ME = 200J and the KE = 150J and is
decreasing, then the PE = 50J and the pendulum is ¾ of the way on its up swing.
Stop! Pretest A covers only concepts 1-48
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49) Chemical energy (CE) is the energy that holds atoms in molecules together. It is a form of potential
energy. Larger molecules have more chemical energy than smaller ones. All stuff has chemical energy!
Examples: sugar (carbohydrates), gasoline (hydrocarbons), ATP (cells), acids/bases - batteries, any type or
fuel or food, all molecules!!! Although CE can hold a lot of energy, it does not have nearly the same
potential as nuclear energy.
50) Law of Conservation of Mass: “Mass (matter) cannot be created or destroyed.” mass in (reactants) =
mass out (products) Where does stuff go when it burns up? Chemical reactions (breaking of atomic bonds)
such as burning gasoline or digesting food releases the stored chemical energy and changes it into another
form of energy (usually heat) which leaves the system. Energy is lost but total mass always stays the same.
Combustion (burning) changes the size and shape of the materials, but the total mass is exactly same before
and after.
51) Nuclear energy (NE) is the energy that holds protons and neutrons together inside the nucleus of an
atom. It is the most powerful energy source every discovered. It is potential energy. Nuclear energy is
produced in two ways. Nuclear fusion is where energy stored in hydrogen atoms join to form helium
releasing large amounts of electromagnetic energy. This is done by our sun. Nuclear fission is where the
nuclei of large atoms are split converting the potential nuclear energy into kinetic electromagnetic energy.
52) Thermal energy (TE) is the total kinetic energy of the particles that make an object. It is the vibration
of all the atoms or molecules within an object. All atoms and molecules are in motion at all times. At room
temperature, atoms jiggle at about 1000 mph. Thermal energy is measured in joules.
53) Temperature is a measure of the average kinetic energy of the particles in an object. It is the intensity
of the motion of the particles. At higher temperatures, particles of matter move faster and have more kinetic
energy. At lower temperatures, particles move slower and have lower kinetic energy. Temperature does not
depend on the size or type of object. For example, the temperature of a small cup of water might be the
same as the temperature of a large tub of water, but the tub of water has more thermal energy because it has
more water. High up in the atmosphere, the temperature increases to over 3600F because gas molecules
absorb solar wind and move very rapidly. But since the molecules are spaced far apart, the thermal energy
is low even though the temperature (degrees Fahrenheit or Celsius) is high.
54) Heat is not exactly the same as thermal energy. Heat is energy that is transferred or moving between
substances due to a temperature difference between them. The amount of heat transferred by a substance
depends on the speed and number of atoms or molecules in motion. The faster the atoms or molecules
move, the higher the temperature, and the more atoms or molecules that are in motion and the greater the
amount of heat they transfer. According to the second law of thermodynamics, heat always flows from
areas of high temperature to areas of low temperature.
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55) Friction is the thermal energy that opposes motion. It includes the heat given off when things touch. It
is the energy transfer or change from mechanical energy to thermal energy.
56) The four states of matter (solid, liquid, gas, plasma) are scientifically defined by the ratio of a matter’s
used atomic bonds to the number of bonds possible. Matter states are more easily and commonly defined by
(a) the amount of chemical and thermal energy and (b) the space between the matter’s molecules.
57) Matter in the solid state has relatively low energy and its molecules are close together. Its molecules
are still moving but very slowly compared to liquids and gases, and not fast enough to overcome the
attraction of other molecules. A high percentage of available bonding is being used
58) Matter in the gas state has a high amount of energy. There is too much energy to allow the atoms to
attract and stick much. The molecules move fast and are far apart.
59) Matter in the liquid state is in between a solid and gas. The atoms move fast enough to overcome some
of the attraction between them. Liquids may change shape but not volume. A plasma state of matter is
super high energy. Atoms are stripped of their electrons so they cannot bond together.
60) Electrical energy (EE) is the movement of electrons through matter. It is kinetic energy. When
electrons are knocked out of their orbit, electricity is created. There are two kinds of electricity - static and
current.
61) Static electricity is the random and scattered movement of electrons in an area where they spread out.
Every time two things touch, they trade electrons and become ions with either a positive or negative charge.
No work is done in static electricity because the electrons are scattered. Sometimes the electrons pile up
and form a charge until they find a conducting path. Lightning is static electricity.
62) Current electricity is the continuous flow of electrons along a directed path called a circuit. Since we
control where the electrons go, work is done. Current always flows from a place where there are many
electrons (negative charge) to a place where there are fewer electrons (positive charge). This movement
creates a loop. Current always flow from negative (-) to positive (+).
63) A complete circuit consists of a source of electrical charges (a power supply such a
battery or generator), a conducting path, and a device that uses the electrical energy
called a resistor. An open circuit is a path for electricity that has been interrupted or
broken. Since there is nowhere for the electrons to go, they stop flowing and turn into static electricity until
the path is reconnected. A short circuit is a path for electricity that has been given an alternate route.
Some or all of the electrons do not flow along the intended path.
64) Electrical energy is measured by its volts, amps, and resistance. Voltage (V) measures the total amount
of electrical energy or force in a circuit. It is the electrical push for electrons. It is sometimes called
electromotive force or EMF. If the flow of electrons is compared to water running downhill in a pipe, then
voltage is the height of the hill pulling or pushing the water.
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65) Amperage, measured in amperes (A), is the amount of electrons passing a point in one second. It
measures the flow rate of electricity. Static electricity may have a high voltage, but it will always have a
low or zero amperage (except for lightning) because the electrons do not all flow the same direction. If the
flow of electrons is compared to water running downhill in a pipe, then amperage is the amount of water
moving through the pipe.
66) Resistance to electron flow is measured in ohms (Ω). Insulators have a high resistance and conductors
have a low resistance. If the flow of electrons is compared to water running downhill in a pipe, then
resistance would be the size of the pipe. Larger wires in a circuit will mean increased flow (higher amps)
but it will also mean increased resistance.
67) Ohm’s Law describes the relationship between voltage, amperage, and resistance in
a circuit. It can be described in a simple equation where E = Voltage, I = Amperage, and
R = Resistance. I = E/R and R = E/I and E = I×R
For example: If the resistance is
10Ω and the amperage is 0.5 A, what is the voltage? 10Ω times 0.5 A = 5V. How much
current is flowing in a circuit with 120 volts and 12Ω? 120V divided by 12Ω = 10A
68) Watts (w) measure power or heat by multiplying voltage times amperage. P = E×I
69) Electrons always flow along the shortest, easiest, most direct path to complete their circuit. Current
always flows the path of least resistance.
70) A series circuit is where electrons have only one path to flow. Each electrical device is connected in a
chain. Electricity must flow through all of the devices in the circuit. Current starts at the negative side and
returns at the positive side. They are easy to construct and use little wire. But, if one device is turned off,
the circuit opens and the current stops. In a
series circuit current flow or amperage remains
constant throughout the whole circuit, but
voltage drops across each device. All devices
share the voltage from the power source (battery,
generator, outlet, etc.). As each device uses the
push or EMF, the voltage is lowered for the next
device. For example, lights in series get dimmer
the farther they are away from the power source.
The voltage drop across each resistor can be
added to find the total voltage of the circuit. To find the total resistance, just add the ohms of the circuit.
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71) A parallel circuit is where electrons have more than one path to flow.
Each electrical device has its own path for electrons. Electricity may flow
around any of the devices in the circuit. If one device is turned off or
disconnected, the circuit is still complete and the current continues. In a
parallel circuit voltage remains constant throughout the whole circuit. So
adding devices does not cause lights to go dimmer, but amperage drops
across each device. All devices share the current from the power source
(battery, generator, outlet, etc.). As each device uses current, the amperage is
lowered for the next device. The current can be added across each device to
find the total current. Since flow rate is reduced, larger wires with more
resistance and a larger power source must be used. So, parallel circuits can be
more costly than series circuits.
72) Most batteries and hand held appliances use direct current (DC). This is electricity that moves in only
one direction through a circuit forming a loop. Since current is constant, each electron must travel through
the entire circuit. DC is not used for large applications where there are lots of devices – houses, cities, etc.
because voltage will drop across each device. So, if DC were to be used to supply large amounts of
electricity for city use, there must be a power station on every city block.
73) Alternating current (AC) is current that constantly switches directions. Instead of going in a loop like
DC, charges are built up and then reversed to go the other direction. Current still moves from negative to
positive, but the negative and positive are constantly switched. This is called reversing polarity. City
lighting and power systems in the US generally operate AC at 60 Hertz (Hz). This means that the electricity
changes directions 60 times per second.
74) Electricity is a secondary source of energy. We must use another energy source to produce it. In the
U.S., coal is the number one energy source used for generating electricity. Electricity is sometimes called
an energy carrier because it is an efficient and safe way to move energy from one place to another.
75) We can use magnets to produce electricity. A magnetic field will push loosely held electrons along a
conductor. Power plants use huge turbine generators to make electricity that we use in our homes and
businesses. The turbine spins really fast by the use of steam or by the use of wind, or rushing water in a
dam. Steam can be produced by various fuel sources such as coal, oil, natural gas, or uranium. In a
generator, the turbine is attached to a shaft. Inside are permanent magnets and coils of wire attached to the
shaft. As the shaft spins, electrons are pushed by the magnetic field. The moving electrons are the
electricity that flows to our houses. Electricity moves very fast. In just one second, it can travel around the
world seven times.
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76) Radiant energy (RE) is the energy from electromagnetic waves. Electromagnetism is a wave of pure
energy defined by its wavelength and frequency (the amount of energy in a space). The electromagnetic
spectrum includes radio waves, TV waves, infrared (heat), visible light, ultra violet, X-rays, gamma rays.
Radiant energy travels at about 186,000 miles per second in a vacuum (absence of matter - space).
77) Each of the seven forms of energy can be changed into any one of the other energy forms. A change in
energy form is called an energy conversion. Often one form is changed into many different other forms.
For example, light energy from the sun is converted into heat energy by the ground and into chemical
energy stored in sugar by photosynthesis in plants. A battery converts chemical energy into electrical
energy. A stereo converts electrical energy into sound energy using the speakers. A combustion engine
converts chemical energy from the gasoline into mechanical energy which pushes the piston down. All
energy comes from other forms of energy. This is the first law of thermodynamics.
78) Energy conversions often involve the changing or movement of matter. There are three types of objects
or areas where matter and energy conversions take place (isolated, closed, open). A system is a place or
object where matter and energy exist and energy conversions take place over a certain period of time.
Systems often exist inside other systems. For example: nervous, cardiovascular, respiratory, muscle, and
skeletal systems all operate together inside the human body system. A machine is a man-made system that
makes work easier by changing the size or direction of the force.
79) Systems try to control the type of energy conversions that happen in order for them to do work. But, not
all the energy in a conversion in a system becomes useful energy. Any time that things touch, they trade
energy and heat is lost which is wasted energy. In totally 100% efficient systems, all the energy put in
does exactly what was intended and is useful. Because parts in a system must touch and trade heat, no
system can ever be 100% efficient
80) An isolated system is an object or area where there is an exchange or transfer of matter and energy only
within the system and none outside to the surrounding - everything stays in or stays out. Perfectly isolated
systems are impossible because they violate the first law of thermodynamics - everything must touch and
trade heat so nothing can be totally isolated and 100% efficient! There are no isolated systems inside the
universe. The only known isolated system is the universe itself as whole. The universe is self contained
and is made of open and closed systems. The main goal of all engineering is to get as close as possible to an
isolated system or 100% efficient machine.
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81) A closed system is an object or area where there is an exchange or transfer of matter and energy within
the system, and where there is no transfer of matter outside, but there is some exchange of energy outside
the system - heat is given off. Because energy leaves but nothing gets in or out, they will eventually run out
of energy or fuel. Most created machines and most natural or biological systems are considered to be closed
at least for periods of time. The following examples are closed systems: a bouncy ball, a battery circuit,
cars, airplanes (after refueling not during), animals (after eating a meal not during)
82) An open system is where there is transfer of both matter and energy both inside and outside different
systems. Matter and energy enter and leave the system. Most machines are not open because there would
need to be constant change in either the amount of work being done or a constant refueling/feeding process.
The following examples are open systems: refrigerator or electric appliances, volcanoes, hurricanes,
tornadoes, weather fronts, solar system.
83) Energy used by humans comes from ten primary sources. They are: biomass, hydropower, wind,
geothermal, solar, petroleum, coal, natural gas, uranium, propane. These sources are dived into two groups:
renewable – humans can produce more, and nonrenewable – it cannot be made.
84) Biomass is any organic matter that can be used as an energy source. Burning wood, crops, and yard and
animal waste are examples of biomass. It is renewable because we can grow more in a short period of time.
Methane is an organic waste gas that can be used as fuel. It is produced naturally by landfills and is the
main ingredient in natural gas. Biofuels such as ethanol are produced by growing crops such as corn,
sugarcane, and algae. Biomass used to provide up to 90% of the energy used in America until about 1850,
but now it makes up only about 4.1% of our total energy consumption in the U.S.
85) Hydropower is energy that comes from the force of moving water. It is a renewable resource because it
is replenished by snow and rainfall. Hydropower plants use turbine generators to produce electricity. A dam
blocks water flow and stores its potential energy. A dam gate is opened to allow water to flow through large
tubes called penstocks. At the bottom, the water moves large turbine blades which are attached to
generators that produce electricity. Hydropower makes up about 2.8% of the total energy consumption in
the U.S. It is the cheapest way to produce electricity in the U.S. today.
86) Wind energy is used to make electricity, but it supplies only about 0.7% of the electricity used in the
U.S. each year. It is a renewable resource. Most wind turbines have the same basic parts. The blowing
wind pushes on turbine blades making them spin. The blades are connected to a driveshaft and gearbox.
The gearbox increases the spinning motion of the shaft which turns the generator. Electricity is sent to a
transmission line. Large turbines are sometimes connected together in wind farms.
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87) The amount of electricity produced by wind depends on the size of the turbine and the amount of wind.
Wind farms can only produce electricity when the wind is blowing at a certain speed. The best sites for
wind farms are on hilltops, open plains, through mountain passes, and near the coast of oceans or large
lakes. Ohio ranks 18th in wind energy potential. Wind power makes up about 0.5% of the total energy
consumption in the U.S.
88) Geothermal energy is heat generated from within the earth. It is a renewable source of energy. We can
dig wells and pump heated, underground water to the surface to heat homes and generate electricity. The
most active geothermal resources are found along tectonic plate borders, volcanoes, hot springs, and
geysers. For producing electricity, power plants are located directly above the fuel source. Geothermal
wells are one to two miles deep. Hot water or steam is piped to a power plant to produce steam that turns a
turbine connected to a generator. The water is returned to the ground in an injection well. Low temperature
water wells can be used for heating and cooling homes and buildings. Geothermal heat pumps circulate
water from the surface to tubes buried in the ground. Geothermal makes up about 0.4% of the total energy
consumption in the U.S.
89) Solar energy is a renewable resource. Today, people use solar energy to heat buildings, heat water, and
generate electricity. The amount of solar energy an area receives depends on the time of day, the season of
the year, the cloudiness of the sky, and how close the location is to the equator. A solar collector changes
sunlight into useable heat energy. A combination of dark colored metal plates, mirrors, and lenses can be
used to trap heat in a building similar to a greenhouse. To make electricity from sunlight, a photovoltaic
cell is needed. The electricity can be stored in batteries or sent to transmission lines. Solar makes up about
0.1% of the total energy consumption in the U.S.
90) Petroleum is a fossil fuel, which means that it is made naturally from the remains of plants and animals.
It is usually called crude oil. It is a nonrenewable resource. Petroleum deposits are locked in porous rocks
underground similar to how water is trapped in a sponge. We can’t use crude oil as it comes out of the
ground because it can be as thin as water or as thick as tar. An oil refinery cleans and separates crude oil
into many types of fuels and products such as gasoline, diesel, jet fuel, or motor oil. Petroleum provides
about 36.5% of the energy we use in the U.S. Most of this energy is used for transportation and
manufacturing. Industry also uses petroleum as a key ingredient in plastics and many other products.
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91) Natural gas is a fossil fuel made from the remains of tiny sea animals. It is a nonrenewable resource.
Natural gas is trapped in porous rocks underground similar to how air is trapped in a sponge. Natural gas is
really a mixture of gases with the main ingredient, about 90%, being methane. About 5% of natural gas is
propane. Natural gas is colorless, odorless, and tasteless so companies add a chemical called Mercaptan to
give it a really strong smell. Industry is the biggest user of natural gas. It is used as an ingredient in many
items such as fertilizer, glue, paint, and detergent. Natural gas is also used in homes and businesses for
heating. It is also used to make electricity. Natural gas makes up about 24.7% of the total energy
consumption in the U.S.
92) Coal is a fossil fuel made from the remains of plants. It is a nonrenewable resource. Coal provides
about 20.9% of America’s energy needs. Some coal is used in the manufacturing of iron, steel, and other
products, but over 90% of the coal mined in the U.S. is used to make electricity. Almost half of our
electricity comes from coal-fired electrical power plants.
93) Uranium is a radioactive metal that is found in rocks. It is used to make nuclear energy. It is a
nonrenewable resource. Nuclear power plants use nuclear fission to produce electricity. Uranium fuel is
formed into pellets. Each pellet is about the size of your fingertip and produces the same amount of energy
as 150 gallons of oil. The pellets are stacked into 12 foot metal fuel rods which are placed at the core or
center of the nuclear reactor. When the rods are moved close together they get extremely hot. The heat is
used to produce steam which turns huge turbine generators to produce electricity. Nuclear power plants
have very little impact on the environment because no fuel is burned and no air pollution is produced. The
used fuel rods must be carefully stored until they lose their radioactivity after about ten years. Uranium
provides about 8.8% of America’s total energy needs, but it provides about 20% of the electricity we use.
94) Propane is a fossil fuel that is usually found underground mixed with deposits of natural gas and
petroleum. It is a nonrenewable resource. Propane is often called LP-gas or liquefied petroleum. Under
normal conditions, propane is a gas. Under pressure, propane is a liquid. Propane is stored and sold as a
liquid fuel in pressurized tanks because it takes up less space. Propane as a gas takes up more than 270
times more space than liquid propane. Just like natural gas, propane is colorless, odorless, and tasteless. So,
companies add a chemical called Mercaptan to give it a really strong smell. Propane is a used by industry
and homes as a heating fuel. It is also used as a transportation and machinery fuel. Propane makes up about
1% of the total energy consumption in the U.S.
Good Job! You are finished! You are ready to take
Pretest B!
Energy efficiency is a comparison of the amount of energy before a conversion with the amount of
useful energy after a conversion. In totally efficient machines, all the energy put in does exactly
what was intended and is useful. Efficiency = Work Out / Work In Efficiency is measured in
percent (smaller divided by the larger number). If an electric motor converts 200J of electric
energy into 180J of total mechanical energy, what is its efficiency? _________________