Science terms and definitions

Term Definition
Mass The quantity of matter in an object. More specifically, it is a measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it, stop it, deflect it, or change its state of motion in any way.
Law of universal gravitation Law which states:every body in the universe attracts every other body with a mutually attracting force. For two bodies this force is directly proportional to the product of their masses&inversely proportional to the square of the distance separating them
Velocity The speed of an object with specification of its direction of motion.
Quantum hypothesis The idea that light energy is contained in discrete packets called quanta.
Entropy The measure of energy dispersal of a system. Whenever energy freely transforms from one form to another, the direction of transformation is toward a state of greater disorder.
Law of reflection The angle of reflection equals the angle of incidence.
Force vector An arrow drawn to scale so that its length represents the magnitude of a force and its direction represents the direction of the force.
Air Resistance The force of friction acting on an object due to its motion through air.
Polyatomic ion Molecules that carry a net electric change.
Kinetic energy Energy of motion, described by the relationship K=mv2
Conservation of momentum Principle which states: in the absence of external force, the momentum of a system remains unchanged. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event: mv(before event)=mv(after event)
Dipole A separation of charge that occurs in a chemical bond because of differences in the electronegativities of the bonded atoms.
Magnetic domains Clustered regions of aligned magnetic atoms. When these regions themselves are aligned with one another, the substance containing them is magnet.
Fact A phenomenon about which competent observers can agree.
Half reaction One portion of an oxidation-reduction reaction, represented by an equation showing electrons as either reactants or products.
Covalent bond A chemical bond in which atoms are held together by their mutual attraction for two electrons they share.
Half life The time required for half the atoms in a sample of radioactive isotope to decay
Scientific method An orderly method for gaining, organizing, and applying new knowledge.
Atomic spectrum The pattern of frequencies of electromagnetic radiation emitted by the atoms of an element, considered to be the elements fingerprints.
Thermonuclear fusion Nuclear fusion produced by high temperature (weak force)
Probability cloud The pattern of electron position plotted over time to show the likelihood of an electrons being at a given position at a given times.
Insulator Any material without free charged particles and through which current does not easily flow.
Atom The smallest particle of an element that has all of the elements chemical properties.
Coulomb The SI unit of electrical charge, equal in magnitude to the total charge of 6.25 x 1018 electrons.
Period The time required for a vibration or a wave to make a complete cycle.
Physical property Any physical attribute of a substance, such as color, density or hardness.
Conduction The transfer of thermal energy by molecular and electronic collisions within a substance (especially a solid)
Ionic bond A chemical bond in which an attractive electric force holds ions of opposite charge together.
Acidic solution A solution in which the hydronium ion concentration is higher than the hydroxide ion concentration.
Friction The resistive force that opposes the motion or attempted motion of an object through a fluid or past another object with which it is in contact.
Electrostatics The study of electric charge at rest( not in motion, as in electric currents).
Heat The thermal energy that flows from a substance of higher temperature to lower temperature, commonly measured in calories or joules.
pH A measure of the acidity of a solution, equal to the negative of the base-10 logarithm of the hydronium ion concentration.
Inverse-square law Law relating the intensity of an effect to the inverse square of the distance from the cause: Intensity~1/distance2.
Conservation of energy and machines Principle which states: the work output of any machine cannot exceed the work input. In an ideal machine, where no energy is transformed into heat, Work input=work output and (Fd) input=(Fd)output.
Neutral solution A solution in which the hydronium ion concentration is equal to the hydroxide ion concentration.
Period A horizontal row in the periodic table.
elemental formula A notation that uses the atomic symbol and(sometimes) a numerical subscript to denote how atoms are bonded in an element,
Critical mass The minimum mass of fissionable material in a reactor or nuclear bomb that will sustain a chain reaction.
Force pair The action-and-reaction set of pushes and pulls that constitute an interaction.
Physical change A change in which a substance changes its physical properties without changing its chemical identity.
Satellite A projectile or small body that orbits a larger body.
Chemistry The study of matter and the transformations it can undergo.
Hypothesis An educated guess or a reasonable explanation.
Oxidation-reduction reaction A reaction involving the transfer of electrons from one reactant to another.
Electric power The rate of energy transfer, or rate of doing work; the amount of energy per unit time, which can be measured by the product of current and voltage. It is measured in watts(or kilowatts)
Science The collective finding of humans about nature, and a process of gathering and organizing knowledge about nature.
Tangential velocity Velocity that is parallel (tangent) to a curved path.
Nuclear fission The splitting of the nucleus of a heavy atom, such as uranium-235, into two main parts, accompanied by the release of much energy.
Conservation of energy Principle which states: in the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed.
Chemical formula A notation used to indicate the composition of a compound, consisting of the atomic symbols for the different elements fo the compound and numerical subscripts indicating the ratio in which the atoms combine.
Ion An electrically charged particle created when an atom either loses or gains one or more electrons.
Condensation A transformation from a gas to a liquid
Shell A set of overlapping atomic orbitals of similar energy levels; in other words, a region of space in which electrons of similar energy levels in an atom have a 90 percent chance of being located.
Control A test that excludes the variable being investigated in a scientific experiment.
Relationship of impulse and momentum Impulse is equal to the change in the momentum of the object upon which the impulse acts. In symbolic notation, Ft= ?mv.
Spectroscope A device that uses a prism or a diffraction grating to separate light into its component colors.
Reduction The process whereby a reactant gains one or more electrons.
Inertia The property of things to resist changes in motion.
Forced vibration The setting up of vibrations in an object by a vibrating source.
Reflection The returning of a wave to the medium from which it came when it hits a barrier.
Direct current(DC) An electric current flowing in one direction only.
Electronegativity The ability of an atom to attract a bonding pair of electrons to itself when bonded to another atom.
Atomic nucleus The core of an atom, consisting of two basic subatomic particles, protons and neutrons.
Thermal (internal) energy The total energy (kinetic plus potential) of the submicroscopic particles that make up a substance.
Impulse The product of the force acting on an object and the time during which it acts.
Radiation The transfer of energy by means of electromagnetic waves.
Maxwells counterpart to faradays law magnetic field induced in any region space which electric field change w/time The magnitude of electric field proportional to rate which electric field changes. direction of induced magnetic field at right angles to changing electric field.
Magnetic field The region of magnetic influence around a magnetic pole or a moving charged particle.
Conductor Any material having free charged particles that easily flow through it when an electric force acts on them.
Momentum The product of the mass of an object and it velocity.
Transverse wave A wave in which the medium vibrates in a direction perpendicular(transverse) to the direction in which the wave travels
Electrically polarized Term applied to an atom or molecule in which the changes are aligned so that one side has a slight excess of negative charge.
Force Simply stated, a push or pull.
Electromagnetic wave A wave of energy produced when an electric charge accelerates.
Electric Field Defined as force per unit charge can b considered to b energetic aura surrounding charged objects.charged point the field decreases w/ distance according to the inversesquare law like a gravitational field oppositely charged parallel plates uniform
Kilogram the unit of mass equals the mass of 1 liter(L) of water at 4C
Electron A negatively charged particle in an atom
Acid A substance that donates hydrogen ions
Alternating current (AC) Electric current that repeatedly reverses its direction; the electric charges vibrate about relatively fixed positions. In the United States, the vibrational rate is 60 Hz.
Principal quantum number (N) An integer that specifies the quantized energy level of an atomic orbital.
Beta particle An electron (or positron) emitted during the radioactive decay of certain nuclei.
Technology The means of solving practical problems by applying the findings of science.
Atomic symbol An abbreviation for an element or atom.
Diffraction Any bending of light by means other than reflection and refraction.
Valence electron An electron that is located in the outermost occupied shell in an atom and can participate in chemical bonding.
Liquid Matter that has a definite volume but no definite shape, assuming the shape of its container
Valence electron An electron that is located in the outermost occupied shell of an atom and can participate in chemical bonding.
Mole 6.02 x 1023 units of anything.
Neutron An electrically neutral subatomic particle in an atomic nucleus.
Atomic orbital A position in an atom in which an electron has a 90 percent chance of being located.
Pseudoscience A theory or practice that is considered to be without scientific foundation but purports to use the methods of science.
Nucleon A nuclear particle; A proton or a neutron in an atomic nucleus.
Radioactivity The process whereby unstable atomic nuclei break down and emit radiation
Base a substance that accepts hydrogen ions.
Electromagnetic spectrum A continuous range of electromagnetic waves extending from radio waves to gamma rays.
Ellipse The sum of the distances from any point on the path to two pints called foci is a constant; also the oval path followed by a satellite.
Compound a material in which atoms of different elements are bonded to one another
Energy The property of a system that enables it to do work
Resonance A dramatic increase in the amplitude of a wave that results when the frequency of forced vibrations matches an objects natural frequency.
Hydrogen bond A strong dipoledipole attraction between slightly positive hydrogen atom on one molecule and a pair of nonbonding electrons on another molecule.
Evaporation A transformation from liquid to gas
Solute Any component in a solution that is not the solvent.
Wavelength The distance from the top of one crest to the top of the next one, or, equivalently, the distance between successive identical parts of the wave.
Electric potential energy The energy a charge possesses by virtue of its location in a magnetic field.
Longitudinal wave A wave in which the medium vibrates in a direction parallel with the direction in which the wave travels.
Atomic number The number that designates the identity of an element, which is the number of protons in the nucleus of an atom; in a neutral atom the atomic number is also the number electrons in the atom.
Gas Matter that has neither a definite volume nor definite shape, always filling any space available to it.
Wave A disturbance that travels from one place to another, transporting energy, but not necessarily matter, along with it.
Law of mass conservation Law which states; matter is neither created nor destroyed during a chemical reaction.
Newtons second law of motion Law which states; the acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.
Protons A positively charged particle in an atomic nucleus
Gamma Ray High-frequency electromagnetic radiation emitted by the nuclei of radioactive atoms
Transparent The term applied to materials through which light can travel in straight lines
Efficiency The percentage of the work put into a machine that is converted into useful work output (energy output divided by total energy input)
Hydroxide ion A water molecule after losing a hydrogen ion.
Periodic trend The gradual change of any property in the elements across a period
Terminal speed The speed at which the acceleration of a falling object stops when air resistance balances weight
Entropy The term used to describe the idea that energy has a natural tendency to disperse Equals the total amount of energy in a given amount of substance divided by the substances absolute temperature.
Frequency The number of to-and-fro vibrations an oscillator makes in a given time; or the number of times a particular point on a wave (for example the crust) passes a point in a given time
Photon A particle of light
Catalyst A substance that increases the rate of a chemical reaction by lowering its activation energy
Convection the transfer of thermal energy in a gas or liquid by means of currents in the heated fluid The fluid flows carrying energy with it
Applied research Research dedicated to the development of widely used products and processes
Boiling Evaporation in which bubbles form beneath the liquid surface
Newtons third law of motion Law which states; whenever one object exerts a force on a second object the second object exerts an equal and opposite force on the first object
Vector components Parts into which a vector can be separated and that act in different directions from the vector
Oxidation The process whereby a reactant loses one or more electrons
Speed The distance traveled per time
Coulombs Law The relationship among force, charge and distance: F=kq1q2/d2 if the charges are alike in sign the force is repelling if the charges are unlike the force is attractive
Valence shell The outermost occupied shell of an atom
Electric Current The flow of electric charge that transports energy from one place to another it is measured in amperes where 1 A is the flow of 6.25 x 1018 electrons per second or 1 coulomb per second
Refraction The bending waves due to a change in the medium
Melting A transformation from solid to liquid
Opaque The term applied to materials that absorb light without remission
Net force The Combination of all forces that act on an object
Metallic Bond A chemical bond in which the metal ions in a piece of solid metal are held together by their attraction to a fluid of electrons in the metal
Semiconductor A material that can be made to sometimes behave as an insulator and sometimes a conductor
Projectile Any object that moves through the air or through space under the influence of gravity
Element Any material that is made up of only one type of atom
Amphoteric A description of a substance that can behave as either an acid or a base
Chemical equation A representation of a chemical reaction
Matter Anything that occupies space
Interaction Mutual action between objects in which each one exerts an equal and opposite force on the first object
Concentration A quantitative measure of the amount of solute in a solution
Electromagnet A magnet whose field is produced by an electric current it is usually in the form of a wire coil with a piece of iron inside the coil
Inelastic collision A collision in which the colliding objects become distorted generate heat and possibly stick together
Transmutation The conversion of an atomic nucleus of one element into an atomic nucleus of another element through a loss or gain in the number of protons
Latent heat Energy that is released or absorbed in a change of phase
Molecule A group of atoms held tightly together by covalent bonds
Strong force The powerful force that attracts nucleons to one another over a short distance
Interference The combined effect of two or more waves overlapping
Quantum A small discrete packet of light energy
Vector quantity A quantity that specifies direction as well as magnitude
Dispersion The separation of light into colors arranged by frequency
Sublimation The change of phase of a solid directly to a gas
Hydronium ion A water molecule after accepting a hydrogen ion
Freezing A transformation from a liquid to a solid
Saturated A solution containing the maximum amount of solute that will dissolve
Equilibrium Rule Rule which states that the vector sum of forces acting on a nonaccelerating object equals zero: SF=0
Doppler effect The charge in frequency of a wave due to the motion of the source( or due to the motion of the receiver)
Alpha particle The nucleus of a helium atom which consists of two neutrons and two protons ejected by certain radioactive elements
Power The time rate of work or rate at which energy is expended described by the relationship P=work/time
Nonpolar bond A chemical bond that has no dipole
Salt An ionic compound formed from the reaction between an acid and a base
Ohms Law The statement that the current in a circuit varies in direct proportion to the potential difference or voltage and inversely with the resistance: Current=voltage/resistance
Chemical reaction A Chemical change
Physical model A representation of an object on some convenient scale
Specific heat capacity The quantity of heat per unit mass required to raise the temperature of a substance by 1 degree celsius
Basic research Research dedicated to the discovery of the fundamental workings of nature
Electric resistance The property of a material that resists the flow of electric current through it it is measured in ohms (O)
Chemical bond The attraction between two atoms that holds them together in a compound
Molarity A unit of concentration equal to the number of moles of a solute per liter of solution
Mass number The total number of nucleons in an atomic nucleus
Coefficient A number used in a chemical equation to indicate either number of atoms/molecules or the number of moles a reactant or product
Theory A synthesis of a large body of information that encompasses well-tested hypotheses about certain aspects of the natural world
Electric potential (voltage) The electric potential energy per amount of charge measured in volts and often called voltage
Solubility The ability of a solute to dissolve in a give solvent
Work energy theorem Principle in which states the work done on an object equals the change in kinetic energy of the object W=?KE
Work The product of the force and the distance through which the force moves W=Fd
Chemical properties A property that relates to how a substance changes its chemical identity
Conceptual model A representation of a system that helps in making predictions about how the system behaves
Acceleration The rate at which velocity changes with time the change in velocity may be in magnitude or in in direction or in both it is usually measure in m/s2
Potential energy The stored energy that a body possesses because of its position
Temperature A measure of the hotness or coldness of substances related to the average translational kinetic energy per molecule in a substance measured in degrees Celsius Fahrenheit or Kelvin
Solution A homogeneous mixture in which all components are dissolved in the same phase
Chemical change During this kind of change atoms in a substance are rearranged to give a new substance having a new chemical identity
First law of thermodynamics A restatement of the law of energy conservation usually as it applies to systems involving changes in temperature whenever heat flows into or out of a system the gain or loss of thermal energy equals the amount of heat transferred
Absolute zero The theoretical temperature at which a substance possesses no thermal energy
Reactant A starting material in a chemical reaction appearing before the arrow in a chemical equation
Elastic collision A collision in which colliding objects rebound without lasting deformation or the generation of heat
Nuclear fusion The combining of nuclei of light atoms to form heavier nuclei with the release of much energy
Magnetic force Between magnets it is the attraction of unlike magnetic poles for each other and the repulsion between like magnetic poles between a magnetic field&a moving charge it is deflecting force due to the motion of the charge deflecting force is perpendicular
Precipitate A solute that has come out of solution
Parallel circuity An electric circuit with two or more devices connected in such a way that the same voltage acts across each one and any single one completes the circuit independently of all the others
Atomic mass The mass of an elements atoms listed in the periodic table as an average value based on the relative abundance of the elements isotopes
Chain reaction A self-sustaining reaction in which the products of one reaction event stimulate further reaction events
Submicroscopic The realm of atoms and molecules where objects are smaller that can be detected by optical microscopes
Joule The SI unit of energy and work equivalent to a newton-meter
Electron-dot structure A shorthand notation of the shell model of the atom in which valence electrons are shown around an atomic symbol
Series circuit An electric circuit with devices connected in such a way that the same electric current flows through each of them
nucleon A nuclear proton or neutron
Group A vertical column in the periodic table also known as a family of elements
Parabola The curved path followed by a projectile near the earth under the influence of gravity only
Free fall Motion under the influence of gravitation pull only
Corrosion The deterioration of a metal typically caused by atmospheric oxygen
Solid Matter that has a definite volume and definite shape
Resultant The net result of a combination of two or more vectors
Newtons first law of motion Law which states every objects continues in a state of rest or in a state of motion in a straight line at a constant speed unless it is compelled to change that state by forces exerted on it
Neutralization A reaction in which an acid and base combine to form a salt
Isotopes Different forms of an element whose atoms contain the same number of protons but different number of neutrons
Nonmental An element located toward the upper right of the periodic table and is neither a metal nor a metalloid
Newton The scientific unit of force
Solvent The component in a solution present in the largest amount
Metalloid An element that exhibits some properties of metals and some properties of nonmetals
Law A general hypothesis or statement about the relationship of natural quantities that has been tested over and over again and has not been contradicted also known as a principle
Second law of thermodynamic Law which states heat never spontaneously flows from a low temperature substance to a high temperature substance Also all systems tend to become more and more disordered as time goes by
Centripetal force Any force that is directed at right angles to the path of a moving objects and tends to prduce circular motion
Potential difference The difference in potential between two points measured in volts and often called voltage difference
Natural Frequency A frequency at which an elastic object naturally tends to vibrate
Universal constant of gravitation That proportionality constant in newtons law of gravitation
Chemical reaction A rearrangement of atoms so that one or more new compound are formed from preexisting compounds or elements
Escape speed The speed that a projectile space probe or similar object must reach in order to escape the gravitational influence of the earth or of another celestial body to which it is attracted
Electromagnetic induction The induction of voltage when a magnetic field changes with time
Combustion An exothermic oxidation reduction reaction between a nonmetallic material molecular oxygen
Product A new material formed in a chemical reaction appearing after the arrow in a chemical equation
Weightlessness A condition encountered in freefall wherein a support force is lacking
Metal An element that is shiny opaque and able to conduct electricity and heat
Support force The force that supports and object against gravity often called the normal force
Diffusion The tendency of molecules to move from an area of high concentration to one of low concentration
Amplitude The distance from the midpoint to the crest (or the trough) of the wave
thermodynamics The study of heat and it transformation to different forms of energy
Periodic table A chart in which all know elements are listed in order of atomic number
Atomic Mass unit (AMU) The standard unit of atomic mass which is equal to one-twelfth the mass of the common atom of carbon arbitrarily given the value of exactly 12
Basic solution A solution in which the hydroxide ion concentration is higher than the hydronium ion concentration
Faradays law Law which states an electric field is induced in any region of space in which a magnetic field is changing with time the magnitude of the induced electric field is proportional to the rate at which the field changes the direction of the induced magnetic
Soluble Capable of dissolving to an appreciable extent in a given solvent
Polar bond A chemical bond that has a dipole
Weight Simply stated the force of gravity on an object more specifically the gravitational force with which a body presses against a supporting surface
Mass The quantity of matter in an object more specifically it is a measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it stop deflect it or change its state of motion in any way
Law of universal gravitation Law which states everybody in the universe attracts every other body with a mutually attracting force for two bodies this force is directly proportional to the square of the distance separating them F=G m1 (;m2/d2
Quantum hypothesis The idea that light energy is contained in discrete packets called quanta

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