a covalent bond in which electrons are not shared equally (p. 168)
a type of light including light with waves that vibrate in only one plane (p. 548)
the regions from latitude 66.5° north to the north pole, and from latitude 66.5° south to the south pole, which are generally cold (p. 753)
a covalently bonded group of atoms that has a positive or negative charge and acts as a unit (p. 172)
a large molecule formed when many smaller molecules are linked together by covalent bonds (p. 275)
voltage, or the difference in electrical potential energy between two places in an electric field (p. 606)
energy that is stored as a result of position or shape (p. 448)
the rate of doing work (p. 414)
a solid that forms and separates from a liquid mixture (p. 57)
a gauge of how exact a measurement is (p. 19)
the result of a force distributed over an area (pp. 75, 390)
three specific colors that can be combined in varying intensities to create millions of colors (p. 552)
new substances formed as a result of a chemical reaction (p. 192)
the curved path of an object in free fall after it is given an initial forward velocity (p. 362)
huge loops of gas that erupt from sunspot regions and extend upward from the photosphere into the chromosphere and sometimes into the corona (p. 833)
a long polymer that forms when amino acids bond together (p. 280)
a positively charged subatomic particle that is found in the nucleus of an atom (p. 108)
a large disk-shaped cloud of dust and gas formed as the solar nebula rotated faster and flattened out (p. 819)
a contracting nebula with enough mass to form a star (p. 841)
a simple machine that consists of a rope that fits into a groove in a wheel (p. 432)
a spinning neutron star that appears to give off strong pulses of radio waves (p. 844)
the opening that allows light to enter the eye (p. 589)
matter that always has exactly the same composition; an element or compound (p. 39)
primary waves; longitudinal waves caused by earthquakes (p. 686)
Q
R
- radiation
the transfer of energy by waves moving through space (p. 481)
- radiation zone
a region of closely-packed plasma outside the core of the sun, where energy is transferred by the absorption and reradiation of light (p. 830)
- radioactivity
the process in which an unstable atomic nucleus emits charged particles and energy (p. 292)
- radioisotope
an isotope with an unstable nucleus (p. 292)
- rarefaction
an area of a longitudinal wave where the particles of the medium are spread out (p. 502)
- ray diagram
a diagram that shows how light rays change direction when they strike mirrors and pass through lenses (p. 570)
- reactant
a substance that undergoes change in a chemical reaction (p. 192)
- reaction rate
the rate at which reactants change into products over time (p. 212)
- reactivity
the property that describes how readily a substance combines chemically with other substances (p. 55)
- real image
a copy of an object formed at the point where light rays actually meet (p. 572)
- red shift
a shift toward the red wavelengths of light from stars or galaxies moving away from Earth (p. 852)
- reflecting telescope
a telescope that uses mirrors and convex lenses to collect and focus light (p. 581)
- reflection
the interaction that occurs when a wave bounces off a surface that it cannot pass through (p. 508)
- refracting telescope
a telescope that uses only lenses to collect and focus light (p. 581)
- refraction
the bending of a wave as it enters a new medium at an angle (p. 509)
- refrigerant
a fluid that vaporizes and condenses inside the tubing of a heat pump (p. 490)
- regular reflection
a reflection that occurs when parallel light waves strike a surface and all reflect in the same direction (p. 547)
- relative age
the age of a rock compared to the ages of other rocks above or below it in a sequence of rock layers (p. 732)
- relative humidity
the ratio of the amount of water vapor in the air to the maximum amount of water vapor that air can contain at that temperature (p. 760)
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