a type of mixture in which the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another (p. 42)
a common unit of power, equal to about 746 watts (p. 416)
a region where a rising column of magma extends from beneath the lithosphere to reach Earth's surface (p. 693)
the Hertzsprung-Russell diagram, a graph of the surface temperature versus absolute brightness of a sample of stars (p. 838)
the direct variation of the speed at which a galaxy is moving away from Earth with its distance from Earth (p. 853)
the amount of water vapor in a given volume of air (p. 760)
a large tropical cyclone with winds of at least 119 kilometers per hour (74 miles per hour) (p. 771)
the process by which ocean waves erode rock (p. 728)
a device that uses a pressurized fluid acting on pistons of different sizes to increase force (p. 395)
an organic compound that contains only the elements hydrogen and carbon (p. 264)
energy obtained from flowing water (p. 463)
a cell that generates electricity from a controlled reaction between hydrogen and oxygen (p. 608)
a proposed answer to a question (p. 8)
I
- ice ages
periods when climates are colder than usual and glaciers cover a large portion of Earth's surface (p. 781)
- ideal mechanical advantage (IMA)
the mechanical advantage of a machine in the absence of friction (p. 423)
- igneous rock
rock that forms from magma or lava (p. 671)
- image
a copy of an object formed by reflected or refracted rays of light (p. 547)
- impermeable
a description of a material through which water cannot easily pass (p. 707)
- incandescent
a description of an object hot enough to glow (p. 558)
- inclined plane
a slanted surface along which a force moves an object to a different elevation (p. 431)
- index fossil
a fossil of a species that is easily identified, occurred over a large area, and lived for a well-defined period of time (p. 733)
- index of refraction
the ratio of the speed of light in a vacuum to the speed of light in a medium (p. 575)
- indicator
a substance that changes color in the presence of an acid or a base (p. 241)
- induction
the transfer of charge without contact between materials (p. 603)
- inertia
the tendency of an object to resist a change in its motion (p. 364)
- inorganic
a description of a material that is not organic (p. 665)
- input arm
the distance between the fulcrum in a lever and the input force (p. 428)
- input distance
the distance through which the input force acts in a machine (p. 419)
- input force
the force exerted on a machine (p. 419)
- instantaneous speed
the rate at which an object is moving at a given moment in time (p. 334)
- integrated circuit
a thin slice of silicon that contains many solid-state components; a microchip (p. 622)
- intensity
the rate at which a wave's energy flows through a given unit of area (pp. 515, 538)
- interference
the interaction of two or more waves that combine in a region of overlap (p. 510)
- internal combustion engine
a heat engine in which the fuel burns inside the engine (p. 487)
- intrusive rock
an igneous rock that forms underground from hardened magma (p. 671)
- inverse proportion
a relationship in which the product of two variables is a constant when all other variables are held constant (p. 23)
- ion
an atom or group of atoms that has a positive or negative charge (p. 159)
- ionic bond
the force that holds cations and anions together (p. 160)
- ionization
the process by which neutral molecules gain or lose electrons (p. 230)
- ionosphere
a region of charged particles, or ions, in Earth's atmosphere that overlaps the lower thermosphere (p. 751)
- iris
the colored part at the front of the eye, which expands and contracts to control the amount of light entering the eye (p. 589)
- irregular galaxy
a galaxy with a disorganized appearance (p. 848)
- isobar
a line on a weather map that connects points of equal air pressure (p. 777)
- isotherm
a line on a weather map that connects points of equal air temperature (p. 777)
- isomers
organic compounds with the same molecular formula but with different structural formulas (p. 265)
- isotopes
atoms of a given element that have different numbers of neutrons and different mass numbers (p. 112)
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