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PHYSICAL SCIENCE VOCABULARYcurrent The flow of electrons through awire or any conductor; measured inamperes with an ammeter.deceleration The rate of change invelocity (speed and/or direction) whenvelocity is decreasing; also callednegative acceleration.decibel The unit of measure for soundintensity, abbreviated dB.decomposition reaction - A chemicalreaction in which a substance breaksdown into two or more simplersubstances.dehydrating agent - A substance thatcan remove water from materials.density The mass per unit volume of amaterial; describes how tightly packed asubstance's molecules are.dependent variable - In an experiment,the factor whose value changes becauseof a change in the independent variable.derived - Unit of measurement obtainedby combining SI units.detergent An organic salt similar tosoap, except that detergents do not formsoap scum in hard water.diatomic molecule - A moleculecomposed of two atoms of the sameelement.diesel engine - An internal combustionengine that compresses a fuel-airmixture so much that it ignites from theheat of compression without a spark.diffraction The bending of wavesaround a barrier.diffraction grating - A piece of glass orplastic with many parallel slits that actslike a prism, causing white light thatpasses through it to separate into itscomponent colors.dilute solution - A solution in which theamount of solute is much less than themaximum the solvent can hold at thattemperature.diode A type of rectifier that allowselectric current to flow in only onedirection.direct current - Electrical current thatflows in only one direction through awire.disinfectant A chemical that killsbacteria, such as alcohol.dissociation – The breaking apart of anionic compound into positive andnegative ions when dissolved in water.doping Adding an impurity to asemiconductor to increase its electricalconductivity.Doppler effect - An increase or decreasein wave frequency, caused by motion ofthe source and/or motion of the observer;applies to all waves.dot diagram - A diagram to representelectrons in the outer energy level of anatom; uses the element symbols anddots.double displacement reaction - Achemical reaction in which two ioniccompounds in solution react, forming aprecipitate, gas, or water.dry cell - A power source that acts as anelectron pump and generates electriccurrent by a chemical reaction; usesthick, pasty electrolyte.ductile – ability of metals to be pulledinto wireseffort arm - The part of a lever onwhich an effort force is applied.effort force - The force applied to amachine when a machine is used to dowork.electric field - An area surrounding anelectron that exerts a force on anythingnearby with an electric charge; strongestnearest the electron and weakens withdistance.electric motor - A device that contains arotating electromagnet that changeselectrical energy to mechanical energy.

PHYSICAL SCIENCE VOCABULARYelectrical power - The rate at whichelectrical energy is converted to anotherform of energy; electrical power isexpressed in watts or kilowatts.electrolyte A substance that separates orforms ions in a water solution, makingthe solution an electrical conductor.electromagnet Strong temporarymagnet made by inserting an iron coreinto a wire coil and passing an electriccurrent through the coil.electromagnetic induction - Process bywhich electrical current is induced in awire when it is moved through amagnetic field.electromagnetic radiation - Transversewaves that transfer energy by radiation;vary in length from very long radiowaves to extremely short gamma waves.electron arrangement - In an atom,how the electrons are distributed in theatom's various energy levels.electron cloud - Region where electronsmost probably are found surrounding thenucleus of an atom.electrons Negatively charged particlesthat move around the nucleus of anatom.electroscope A device containing twosuspended metal leaves in a jar thatmove apart when charged; used to detectthe presence of electric charges.element Substance in which all theatoms in a sample are alike.endothermic reaction - A chemicalreaction in which energy is absorbed.energy The ability to cause change.energy farming - The growing of plantsfor use as fuel.energy transfer - The movement ofenergy from one object to another; forexample, thermal energy flowing as heatfrom a heated stove to a skillet.ester An organic compound formed byreacting an organic acid with an alcohol.evaporation The gradual change of asubstance from a liquid to a gas attemperatures below the boiling point.exothermic reaction - A chemicalreaction in which energy is released.Outward movement of molecules awayfrom one another so that they occupy alarger space.expansion combustion engine - Anengine in which the fuel is burnedoutside the engine.experiment An organized procedure fortesting a hypothesis; typically has acontrol and dependent and independentvariables.farsighted Describes a person who seesfaraway things clearly, but has troublefocusing on nearby objects.fiberglass Hairlike strands of glass thatmake a good insulator when arranged inpuffy layers.filter In working with light, a device thatallows one or more colors to betransmitted while others are absorbed orblocked.flammable A chemical characteristic ofa substance that allows it to oxidizerapidly.fluid Any material that flows, such asliquids and gases.fluorescence Occurs when a materialabsorbs ultraviolet radiation thatstimulates it to radiate visible light.fluorescent light - Light produced whenultraviolet radiation inside a fluorescentlight bulb causes its fluorescent coatingto glow.focal length - The distance from thecenter of a lens or mirror to its focalpoint.focal point - A point on the optical axisof a concave mirror or convex lenswhere the light rays come together.force A push or pull one body exerts onanother.

PHYSICAL SCIENCE VOCABULARYfractional distillation - A process basedon boiling points used in oil refineries toseparate the chemical compounds incrude oil into gasoline, kerosene, andother products.fractionating towers - Towers at oilrefineries used for fractional distillationof petroleum.free fall - How an object moves in spacewhen it is influenced only by gravity.freon A refrigerant gas used inrefrigerators and air conditioners.frequency The number of wave creststhat pass a point during one second;expressed in hertz.frequency modulated - Radio waveswhose frequency is varied with voice,music, video, or data for transmissionover long distances.friction The force that opposes motionbetween two surfaces that are touchingeach other.fuel rod - A metal rod filled withuranium pellets, used as the fuel in anuclear reactor.fulcrum The fixed point around which alever pivots.fuse A device that protects an electricalcircuit.galvanometer An instrument used todetect electric currents.gamma rays - High frequencyelectromagnetic waves that travel at thespeed of light, have no mass or charge,and are the most penetrating form ofradiation.gamma rays - High frequencyelectromagnetic waves that travel at thespeed of light, have no mass or chargeand are the most penetrating form ofradiation.gaseous solution - A homogeneous gasthat is composed of two or more gases.gasohol A mixture of ethanol andgasoline that is a useful substitute forgasoline, but whose production may bedamaging to the environment; a biomassfuel.gear A wheel with teeth around its edgedesigned to mesh with teeth on anothergear so as to transfer force and motion.gelatin A substance obtained by boilinganimal bones; used in glues and goods.generator A device that useselectromagnetic induction to induceelectrical current by rotating loops ofwire through a magnetic field.geothermal energy - Thermal energysource located far below Earth's crust.glass A ceramic mixture with no regularcrystal structure.graduated cylinder - A cylinder markedwith volume scale, used in laboratoriesfor measuring liquid volumes.graph A visual display of information ordata organized to help people interpret,understand, or quickly find information.graphite A mineral made of carbonatoms arranged in layers that easily slidepast one another, forming a drylubricant.gravity Force exerted by every object inthe universe on every other object. Theamount of force depends on the massesof the objects and the distance betweenthem.grounded Electrically connected toEarth, either directly or through a wire orother metal object.group In the periodic table, each of the18 vertical columns of elements; eachgroup is made up of elements withsimilar properties.hacker A person who uses a computerto break into other computer systemswithout permission.half life - The amount of time requiredfor one-half of the nuclides in a sampleof radioactive isotope to decay.

PHYSICAL SCIENCE VOCABULARYhalogens Highly active elements inperiodic table Group 17; they have sevenelectrons in their outer shells and readilycombine with Group 1 elements.heat Thermal energy that flows from awarmer material to a cooler material.heat engine - A device that convertsthermal energy that is produced byburning fuel into mechanical energy.heat mover - A device that movesthermal energy from one location andreleases it in another location having adifferent temperature.heat of fusion - The amount of energyneeded to change a material from thesolid state to the liquid state.heat of vaporization - The amount ofenergy needed to change a material froma liquid to a gas.herbicide A chemical poison that killsundesirable plants.hertz The unit of measure for frequency.heterogeneous mixture - A mixture inwhich different parts can be easilydistinguished.homogeneous mixture – A mixture inwhich different materials are blendedevenly so that the mixture is the samethroughout; also called a solution.hydrate A compound that has watermolecules chemically attached to its ionsand written into its formula.hydraulic Describes a system operatedby the energy of moving water.hydrocarbon A compound containingonly carbon and hydrogen atoms.hydronium ion - The ion that makes asolution acidic.hypothesis A testable prediction used tosee how something works or to solve aproblem.incandescent light - Light produced bya thin tungsten wire, or filament, that isheated in an incandescent bulb until itglows.inclined plane - A simple machineconsisting of a sloping surface used toraise objects.incoherent light - Light rays that arenearly parallel, but spread out becausetheir electromagnetic waves do nottravel in the same direction.ideal machine - A machine in whichwork input equals work output; such aperfect machine would be frictionlessand 100 percent efficientindependent variable - In anexperiment, the factor adjusted to adifferent value by the experimenter tosee what effect it will have on thedependent variable.indicator An organic compound thatchanges color in an acidic solution or abasic solution.induction Electrically charging anobject or creating an electrical current init, without physically touching it.inertia The tendency of an object toresist any change in its motion. Ifmotionless, it tends to remain at rest; ifmoving, it tends to keep moving at thesame speed and in the same direction.infrared radiation - Electromagneticwaves that have a wavelength slightlylonger than visible light; indicates thepresence of heat.infrasonic waves - Waves at frequenciesbelow the limit of human hearing.inhibitor A substance that slows orprohibits a chemical reaction.instantaneous speed - The rate ofmotion at a given instant in time.insulator A material that does not allowheat or electrons to move through iteasily.integrated circuit - A thin slice ofsilicon, often less than 1 cm on a side,which can contain thousands of resistors,diodes, and transistors; used in computerand electronic equipment.

PHYSICAL SCIENCE VOCABULARYintensity In sound waves, the amount ofenergy in each wave.interference The ability of two or morewaves to combine to form a new wave.internal combustion engine - Anengine in which fuel is burned inside theengine in chambers.ion A positively or negatively chargeatom.ionic bond - A type of chemical bondformed by the attraction betweenopposite charges of the ions in an ioniccompound.ionization The breaking apart of certainpolar substances to form ions whendissolved in water.isomers Compounds that have identicalchemical formulas but differentmolecular structures and shapes.isotopes Atoms of the same element thathave different numbers of neutrons.joule The basic unit of energy and work.kelvin The SI unit of temperature.kilogram The SI unit of mass.kilowatt hour - The unit of electricalenergy.kinetic energy - Energy in the form ofmotion, as in a moving car or truck.kinetic theory of matter - The idea thatall matter is made up of constantlymoving, tiny particles.lanthanide Any of the 14 metallicelements having atomic numbers 58-71;used in magnets, ceramics, andtelevision picture tubes.laser A device that emits a beam ofphotons that travel in the same directionand phase, producing a beam of coherentlight.Law of conservation of energy - A lawstating that energy can change form butcannot be created or destroyed underordinary conditions.Law of conservation of mass - A lawstating that matter is neither created nordestroyed during a chemical change.Law of conservation of momentum - Alaw stating that the total momentum of agroup of objects is conserved unless anet force acts on the objects.lever A simple machine consisting of abar that is free to pivot around a fixedpoint.line graph - A type of graph used toshow trends or continuous change bydrawing a line that connects data points.lipids Fats, oils, and related organiccompounds.liquid solution - A liquid solvent thathas dissolved in it a gas, liquid, or solid.liter The unit of liquid volume thatoccupies the same volume as a cubicdecimeter and is slightly larger than aquart.loudness The human perception ofsound intensity.lubricant A substance used to reducefriction between two surfaces that movetogether; for example, oil,grease, or graphite.machine A device thatmakes work easier bychanging the size of theforce applied to it and/or the direction ofthe force.magnetic bottle - A powerful magneticfield that creates a container to hold thehydrogen plasma needed for a nuclearfusion reaction.magnetic domains - Groups of atomswith aligned magnetic poles.magnetic field - The region around amagnet where magnetic forces act.magnetic poles - The two ends of apiece of magnetic material where themagnetic forces are strongest, labelednorth pole and south pole.

PHYSICAL SCIENCE VOCABULARYmagnetism A property of somematerials in which there is a force ofrepulsion or attraction between certainlike and unlike poles.magnifier A device thatmakes things appear larger sothat more detail can be seen;for example, a microscope.malleable Ability of metals to behammered or rolled into thin sheets.mass A measurement of the amount ofmatter in an object.mass number - Sum of the number ofprotons and neutrons in an atom'snucleus.mechanical advantage - The number oftimes a machine multiples the effortforce applied to it.mechanical energy - The total amountof kinetic energy and potential energy ina system.medium A material through which awave travels.melt The changing of a substance from asolid state to a liquid state when heatedabove the substance's freezing/meltingpoint.melting point - The temperature atwhich a solid changes to a liquid.metallic bonding - The type of chemicalbond in which positively charged ionsare surrounded by freely movingelectrons.metalloids Elements having propertiesof both metals and nonmetals.metals Elements usually having thesecommon properties: shiny, goodconductors of heat and electricity, aresolids at room temperature.meter The SI base unit of length.microprocessor The computer's "brain."It receives input and tells the computerhow to respond.microscope A opticalinstrument that uses twoconvex lenses withrelatively short focallengths to magnify small,close-up objects.microwaves Radio waves with thehighest frequency and energy; used incommunications and microwave ovens.mixture A material made of elements orcompounds stirred together but notcombined chemically.model A symbolic representation of anidea, system, or structure to makesomething understandable.modulation Process of adding voice,music, video, computer information, orother data to radio waves by usingelectrical currents to vary eitheramplitude or frequency.momentum A property of any movingobject; the product of an object's massand velocity.monomers Organic molecules that arestrung together to form polymers.music Sound created using specificpitches, sound quality, and regularpatterns.nearsighted Describes a person whosees nearby things clearly, but hastrouble focusing on distant objects.net force - The sum of the forces on anobject when unbalanced forces areapplied to it.neutralization A chemical reactionbetween an acid and a base.neutralize To change an acidic solutionor a basic solution so that it is neutral.neutron Atomic particle with no chargethat is part of an atom's nucleus.Newton's first law of motion Describes the relationship betweenvelocity and forces. An object moving ata constant velocity keeps moving at thatvelocity unless a net force acts on it.

PHYSICAL SCIENCE VOCABULARYNewton's second law of motion Describes the acceleration of an object inthe direction of the net force applied toit.Newton's third law of motion Describes action-reaction pairs; forevery action force, there is an equal andopposite reaction force.NIMBY Not in my backyard; a point ofview that supports an issue such asnuclear generation of electricity as longas it does not take place close to home.noise Sound that has no regular patternor definite pitch.nonelectrolyte A substance, such aspure water, that does not conductelectricity.nonmetals Elements that usually aregases or brittle solids at roomtemperature; most do not conduct heat orelectricity well.nonpolar molecule - A molecule thatdoes not have oppositely charged ends.nonrenewable resources - Resourcessuch as coal, oil, and natural gas, whichcannot be replaced after they are usedup.normal In the study of light, animaginary line drawn perpendicular to areflecting surface or perpendicular to amedium that light is entering.nuclear fission - Process in which anatom's nucleus is split into two nucleiwith smaller masses.nuclear fusion - Process in which twoatomic nuclei with low masses are fusedinto a single nucleus of larger mass; alsoknown as a thermonuclear reaction.nuclear reactor - A device thatgenerates electricity from a controllednu

PHYSICAL SCIENCE VOCABULARY carbon 14 dating - Age-determining method for carbon-containing objects up to 50,000 years old. catalyst-A substance that speeds a chemical reaction without itself being permanently changed. cathode ray tube (CRT) - Sealed glass vacuum tube that uses electron