Absolute Zero the Lowest Possible Temperature Where Molecules Have The
Glossary
A
absolute zero – the lowest possible temperature where molecules have the
lowest energy they can have; 0 K on the Kelvin temperature scale.
absorption – the decrease in amplitude of a wave as it passes through a material
and loses energy.
acceleration – the change of speed over time.
acceleration due to gravity (g) – an acceleration of an object due to Earth’s
gravitational field strength; equal to 9.8 m/sec2.
acoustics – the science and technology of how sound behaves.
activation energy – the energy needed for a chemical reaction to break the
chemical bonds in the reactants.
additive color process – a process that creates color by adding proportions of
red, green, and blue together.
additive primary colors – red, green, and blue.
air resistance – the opposing force on a moving object due to friction of air.
alpha decay – radioactive decay that results in an alpha particle (a helium
nucleus) being emitted from the nucleus of an atom.
alternating current (AC) – an electric current (or voltage) that oscillates in
direction. Household AC reverses its voltage 60 times per second.
ammeter – an instrument for measuring electric current flow.
amorphous – a type of solid matter in which the atoms have no repeating order,
the opposite of crystalline.
ampere (amp or A) – the unit for measuring electrical current.
amplitude – the maximum distance from the average in harmonic motion;
amplitude is often a distance or an angle.
analysis – the detailed interpretation of experimental results to determine what
they mean.
angle of incidence – the angle between the incident ray and the normal line.
angle of reflection – the angle between the normal line and the reflected ray.
angle of refraction – the angle between a refracted ray and the normal.
angular speed – the rate at which an object rotates or revolves.
antimatter – matter which has the opposite charge (and other properties) from
normal matter; an anti-electron (positron) has a positive charge while a
normal electron has a negative charge.
Archimedes’ principle – a principle that states that the force exerted on an object
in a liquid is equal to the weight of the fluid displaced by the object.
armature – the rotating part of an electric motor
atom – the smallest particle of an element that can exist alone or in combination
with other atoms.
atomic number – the number of protons that an atom contains.
atomic theory – a theory that states that all matter is composed of tiny particles
called atoms.
axis of rotation – the line around which an object rotates.
B
battery – a device that transforms chemical energy to electrical energy.
beat – the oscillation of amplitude that results from the interference of two sound
waves with frequencies that are close but not exactly equal
Bernoulli’s principle – the law of conservation of energy as applied to fluid flow;
height, pressure and speed of a fluid are related by energy conservation along
a streamline.
beta decay – radioactive decay that results in a beta particle (an electron) being
emitted from the nucleus of an atom.
big bang – a theory of the origin of the universe in which the universe was once
smaller than an atom and began to expand with a huge explosion.
black hole – an compact, astronomical object with such strong gravity that its
escape velocity is equals or exceeds the speed of light.
boundaries – an edge or surface where conditions or materials change.
Boyle’s law – states that the pressure of a gas is inversely proportional to its
volume at constant temperature.
brittleness – a measure of a material’s tendency to break rather than stretch.
brushes – allow current to flow into the coil of an electric motor.
buoyancy – a measure of the upward force a fluid exerts on an object.
C
calorie – a unit of energy equal to 4.184 joules; the quantity of heat energy
required to raise the temperature of one gram of water by 1°C.
capacitance – a measure of a capacitor’s ability to store charge.
capacitor – a device that stores electric charge by keeping positive and negative
charges separated.
Celsius scale – a temperature scale on which zero equals the temperature that
water freezes (0°C) and 100 is the temperature that water boils (100°C).
center of gravity – the average position of an object’s weight.
center of mass – the point at which an object naturally spins.
centrifugal force – the effect of inertia on an object moving in a curve;
centrifugal force is not a true force.
centripetal force – a force that causes an object to move in a circle.
chain reaction – occurs when the fission reaction of a single atom triggers more
nuclear reactions and results in the continuous release of nuclear energy.
charge – a fundamental electrical property of matter that can be positive, zero,
or negative; causes electrons (-) and protons (+) to attract each other.
charged – an object whose net charge is not zero.
charging by contact – the transfer of electric charge between two different
objects by touching them together.
charging by friction – the transfer of electric charge between two different
objects by rubbing them together.
charging by induction – the transfer of electric charge between two objects
without direct contact.
Charles’ law – states that the volume of a gas increases with increasing
temperature if pressure is held constant.
chemical bond – the strong attractive force that holds together atoms in
molecules and crystalline salts.
chemical energy – the energy that is stored in the chemical bonds that join atoms.
chemical equation – chemical formulas and symbols that represent a chemical
reaction.
chemical properties – properties that can only be observed through a chemical
change.
chemical reaction – the breaking and/or forming of chemical bonds that arrange
or re-arrange atoms into different molecules or compounds; relationship
between reactants and products.
circuit diagram – a schematic drawing of an electric circuit.
circular wave – waves whose crests form a pattern of circular wave fronts.
circumference – the measure of the distance around a circle.
closed circuit – a circuit in which there is a complete path for current to flow.
CMYK color process – another name for the subtractive color process that uses
cyan, magenta, yellow, and black pigments.
cochlea – a tiny, fluid-filled structure in the inner ear that contains the nerves that
create your sense of hearing.
coil – a current-carrying wire made into loops.
collision – occurs when two or more objects hit each other.
color – the perception of the energy of light; red light has the lowest energy that
we can see, and violet light the highest.
commutator – the device that switches the direction of electrical current in the
electromagnets of an electric motor.
compass – a device containing a magnet that interacts with Earth’s magnetic
field to indicate direction.
components – the set of perpendicular vectors that add up to a given vector.
compound – a substance made of two or more elements that cannot be separated
by physical means.
conductor – a material that easily carries electrical current.
cones – photoreceptor cells in the eye that respond to color.
consonance – a combination of sound frequencies that is agreeable or
harmonious.
constant speed – a speed that does not change.
constructive interference – occurs when waves add up to make a larger
amplitude.
control variable – a variable in an experiment that is kept the same throughout
the experiment.
convection – the transfer of thermal energy by the motion of a fluid.
converging lens – a lens that bends light rays so they come together; usually a
convex lens.
coulomb (C) – the unit of electric charge.
Coulomb’s law – the formula that says the force between two electric charges is
proportional to the product of the two charges divided by the square of the
distance between them.
covalent bond – a type of chemical bond that is formed when two atoms share
electrons.
crest – the top or highest points on a wave.
critical angle – the angle at which light is totally reflected back into a material.
crystalline – a solid having an orderly, repeating pattern arrangement of atoms
or molecules.
cycle – a unit of oscillation that repeats over and over.
D
damping – the gradual loss of amplitude of an oscillator.
deceleration – a decrease in speed.
decibel (db) – the unit for measuring the loudness of sound.
density – a property that describes the ratio of mass to volume.
dependent variable – the variable in an experiment that changes in response to
choices made by the experimenter; the dependent variable is plotted on the
y-axis of a graph.
destructive interference – occurs when waves add up to make a smaller
amplitude.
diamagnetic – a type of matter in which the magnetic fields of individual
electrons cancel out, leaving each atom with zero magnetic field.
diffraction – the change in shape of a wave as it passes through openings or bends
around an edge.
diffraction grating – an optical device with a series of thin, parallel grooves that
creates an interference pattern of light.
diffraction pattern – the interference pattern of bright and dark bands of light
created by a diffraction grating.
diffuse reflection – the scattering of light into many directions off a non-shiny
surface.
direct current (DC) – electrical current flowing in one direction only.
dispersion – describes the variation in the refractive indices of different colors
of light.
displacement – the distance and direction between the starting and ending points
of an object’s motion; displacement is a vector quantity.
dissonance – a combination of sound frequencies that is discordant or unsettling.
distance – the length of space between two points.
diverging lens– a lens that bends light rays so they spread apart; usually a
concave lens.
Doppler effect – the shift in frequency caused by the relative motion of the
sound source and observer.
E
efficiency – the ratio of a machine’s output work to input work.
elastic collision – occurs when objects collide so that the total kinetic energy
remains the same before and after the collision.
elasticity – a measure of a solid’s ability to stretch and then return to its original
shape and size.
electric circuit – any complete path through which electricity travels.
electric current – the flow of electric charge.
electric field – the electric force in newtons per coulomb created in the space
around an electric charge.
electric motor – a machine that converts electrical energy into mechanical
energy.
electrical energy – the type of energy resulting from electric current.
electrical symbol – a simple symbol used for parts of a circuit in circuit diagrams.
electrically neutral – an object that has equal amounts of positive and negative
charges and whose net charge is zero.
electromagnet – a magnet created by electric current flowing in wires; a simple
electromagnet can be made by inserting an iron core into a wire coil that is
conducting an electrical current.
electromagnetic force – a force created by electricity (charge) or magnetism.
electromagnetic induction – the process of using a moving magnet to create a
current or voltage.
electromagnetic spectrum – the entire range of electromagnetic waves,
including all possible frequencies.
electromagnetic wave – a wave of oscillating electric and magnetic fields that
moves at the speed of light; light is an example.
electron – a low-mass particle with a negative charge that occupies the energy
levels in an atom outside the nucleus; electrons are involved in chemical
bonds and reactions.
electroscope – an instrument used to detect charged objects.
element – a pure substance that contains only atoms with the same atomic
number (number of protons in the nucleus).
ellipse – a particular mathematical kind of “oval” shape; an ellipse is the shape
of the orbit of a comet.
endothermic reaction – a chemical reaction in which requires a net input of
energy.
energy – a fundamental quantity of the universe; measure of ability to change or
create change; energy is required to make a force do work, change motion,
raise temperature, create new matter, break chemical bonds, or push electric
current through a wire.
energy conversion – also energy transformation; the changing from one kind of
energy to another kind of energy; for example, an energy conversion occurs
when potential energy is converted to kinetic energy.
energy flow diagram – a diagram showing the transformations and conversions
of energy in a system.
energy level – one of the discrete values of energy that electrons in an atom are
allowed to have.
energy of pressure – the energy stored in the pressure of a fluid.
English system – a system of measuring that uses distance units of inches, yards,
and miles.
equilibrium – (1) occurs when the forces on an object are balanced and the net
force equals zero; (2) in harmonic motion, the resting position of the system
where the system is undisturbed with no net force.
evaporation – the process by which atoms or molecules leave a liquid and
become a gas at a temperature below the boiling point.
exothermic reaction – a chemical reaction in which there is a net release of
energy.
experiment – any situation that is specifically set up to observe what happens.
experimental variable – a variable in an experiment that is changed by the
experimenter; the variable which is plotted as an independent variable on the
x-axis of a graph.
F
Fahrenheit scale – a temperature scale on which water freezes at 32 degrees
Fahrenheit (or 32°F) and water boils at 212°F.
farad (F) – the unit of capacitance.
Faraday’s law of induction – states that the voltage induced in a coil is directly
proportional to the rate of change of the magnetic field through the coil.
ferromagnetic – a material (like iron) with very strong magnetic properties.
fiber optics – thin glass fibers that use total internal reflection to carry light.
field – a quantity that has a value everywhere in space; how forces are