# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
M
machine: A device that transmits and modifies force.
macromolecule: The term used for a covalent lattice arrangement (e.g. diamond).
magma: Molten rock material generated within Earth.
magnetic field: A region in space around a permanent magnet or electric current that will move other magnetic materials or electric currents.
magnetic force: A field force that acts on a magnet, some metals, or wire carrying a current.
magnetic polarity: The direction of the north-south line of a magnet.
magnetite: A mineral with magnetic characteristics.
malleability: The ability of a substance to be beaten or bent into sheets.
mantle: The zone surrounding Earth’s core and comprising approximately 83 percent of Earth’s volume. It is less dense than the core and is thought to be composed largely of peridotite.
mass: A property of matter.
matter: The physical substance that makes up the universe.
mechanical advantage: This relates to a machine and is equal to the size of the load force divided by the size of the effort force.
melting: A change in state from a solid to a liquid.
melting point: The temperature at which a solid changes state to a liquid.
mesosphere: A layer of the atmosphere between 50 km and 80 km from Earth’s surface.
metallic bonding: The bonding that occurs in a metal.
metamorphic rock: Any rock type altered by high temperature and pressure and the chemical activities of fluids (e.g. slate, gneiss, marble).
meteor: A track of light in the sky from rock or dust burning up in Earth’s atmosphere.
meteorite: An interplanetary chunk of rock after it impacts on a planet or moon, especially on Earth.
microwave: A mid- to low-energy type of electromagnetic radiation.
Milky Way: The band of light in the sky from the stars and dust that make up our galaxy.
millibar (mb): A unit of air pressure. 1 mb = 1 hPa (hectopascal).
mineral: A naturally occurring, inorganic, crystalline solid having characteristic physical properties and a narrowly defined chemical composition.
miscible: The ability of substances to form a homogeneous solution.
mixture: A combination of two or more different substances.
model: A representation. Models are used to give visual representations of the microscopic world.
modified Mercalli intensity scale: A scale that measures the kinds of damage done by an earthquake.
moho: The boundary between Earth’s crust and mantle.
Mohs hardness scale: A scale of the hardness of rock.
molecular formula: The symbolic representation of a molecule’s components.
molecule: Two or more atoms held together by covalent bonds.
monomer: A compound made up of small molecules that are able to form long-chain molecules.
motion energy: A common name given to kinetic energy.