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an eye condition in which objects at any distance appear blurry because of the distorted shape of the cornea

aromatic hydrocarbons

hydrocarbons that contain a ring structure similar to benzene

Archimedes' principle

the equivalence of the buoyant force on an object and the weight of the fluid displaced by the object


a point of maximum displacement midway between two nodes in a standing wave


an ion with a negative charge

central heating system

a heating system that heats many rooms form one central location


an ion with a positive charge


a substance that affects the rate of a chemical reaction without being used up in the reaction


a compound composed of carbon, hydrogen, and oxygen in which the ration of hydrogen to oxygen atoms is 2 : 1


an optical instrument that records an image of an object

concave lense

a lens that is curved inward at the center and is thickest at the outside edges


a programmable device that can store and process information


an area of a longitudinal wave where the particles of the medium are close together

compound machine

a combination of two or more simple machines that operate together


a substance that is made from two or more simpler substances and can be broken down into those simpler substances


the phase change in which a gas or vapor changes directly into a solid without first changing into a liquid


the ration of a material's mass to its volume

decomposition reaction

a chemical reaction in which a compound vbeaks down into two or more simpler substances


a unit that compares the intensities of different sounds


solids whose particles are arranged in a lattice structure

electric force

the attraction or repulsion between electrically charged objects

electric field

a field in a region of space that exerts electric forces on charged particles; a field produced by electric charges or by chaging magnetic fields

electric current

a continuous flow of electric charge

electric circut

a complete path through which electric charge can flow

electric charge

a property that causes subatomic particles such as protons and electrons to attract or repel one another

energy conservation

the practice of finding ways to use less energy or to use energy more efficently


the ability to do work

endothermic reaction

a chemical reaction that absorbs energy from its surroundings


a description of a change in which a system absorbs energy from its surroundings


a substance that cannot be broken down into simpler substances


a force that opposes the motion of objects that touch as they move past each other

frequency modulation (FM)

the number of complete cycles per unit time for a periodic motion

free fall

the movement of an object toward Earth because of gravity

frame of reference

a system of objects that are not moving with respect to one another

fossil fuels

rich deposits of hydrocarbon mixtures that formed from the remains of organisms

hertz (Hz)

the unit of measure for grequency, equal to one cycle per second

heat pump

a device that uses work to transfer thermal energy from a colder area to a warmer area

heat of vaporization

the energy a substance must absorb in order to change from a liquid to a gas

heat of fusion

the energy a substance must absorb in order to change from a solid to a liquid

heat energy

any device that converts thermal energy into work


the interaction of two or more waves that combind in a region of overlap


the rate at which a wave's energy flows through a given unit of area

integrated circuit

a thin slice of silicon that contains many solid-state components; a microchip

instantanious speed

the rate at which an object is moving at a given moment in time

input force

the force exerted on a machine


the state of matter in which a material has a definite volume but not a definite shape

linear graph

a graph in which the displayed data from a straight line


an upward force due to a pressure difference between the top and bottom of a wing


a rigid bar that is free to move atound a fixed point


an object made of any thin, transparent material that has one or two curved surfaces that can reg

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