Unit 2 Matter and Change

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matter
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anything that has mass and takes up space
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element
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a substance that cannot be separated or broken down into simpler substancesby chemical means; all atoms of an element have the same atomic number
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atom
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the smallest unit of an element that maintains the properties of that element
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compound
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a substance made up of atoms of two or more different elements
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molecule
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the smallest unit of a substance that keeps all of the physical and chemical properties of that substance
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diatomic molecule
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a molecule consisting of two atoms
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chemical formula
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a combination of chemical symbols and numbers to represent a substance
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pure substance
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a sample of matter; either a single element or a single compound, that has definite chemical and physical properties
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mixture
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a combination of two or more substances that are not chemically combined
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solution
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a homogeneous mixture of two or more subtances uniformly dispersed throughout a single phase
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physical property
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a characteristic of a substance that does not involve a chemical change, such as density, color, or hardness
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density
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a ration of the mass of a substance to the volume of the substance
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melting point
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the temperature and pressure at which a solid becomes a liquid
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boiling point
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the temperature at which a liquid becomes a gas
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homogeneous mixture
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a mixture in which substances are evenly distributed throughout the mixture
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heterogeneous mixture
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A mixture in which different materials can be distinguished easily
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chemical property
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a property used to characterize materials in reactions that change their identity
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reactivity
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ready susceptibility to chemical change
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flammability
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a material’s ability to burn in the presence of oxygen
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physical change
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a change from one state (solid or liquid or gas) to another without a change in chemical composition
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dissolving
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the process of a material becoming incorporated uniformly into another, or of two materials mixing together evenly
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chemical change
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(chemistry) any process determined by the atomic and molecular composition and structure of the substances involved
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kinetic theory
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(physics) a theory that gases consist of small particles in random motion
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solid
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of definite shape and volume
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amorphous solid
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A solid made up of particles that are not arranged in a regular pattern
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crystalline solid
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solids in which the particles are arranged in a repeating, 3-D pattern, has a specific melting point
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liquid
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a substance in the fluid state of matter having no fixed shape but a fixed volume
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surface tension
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a phenomenon at the surface of a liquid caused by intermolecular forces
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gas
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matter that does not have a definite shape or volume
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plasma
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(physical chemistry) a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors
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temperature
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the degree of hotness or coldness of a body or environment (corresponding to its molecular activity)
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energy
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(physics) the capacity of a physical system to do work
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thermal energy
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total amount of energy associated with the random movement of atoms and molecules in a sample of matter
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melting
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the process whereby heat changes something from a solid to a liquid
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evaporation
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the process of becoming a vapor
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sublimination
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the change of a substance from a solid to a gas
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condensation
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the process of changing from a gaseous to a liquid or solid state
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freezing
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the change of state from a liquid to a solid
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law of conservation of mass
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a fundamental principle of classical physics that matter cannot be created or destroyed in an isolated system
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law of conservation of energy
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the fundamental principle of physics that the total energy of an isolated system is constant despite internal changes

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