Introduction: Matter and Measurement

chemistry
the scientific discipline that studies the composition, properties, and transformations of matter
matter
anything that occupies space and has mass; the physical material of the universe
element
a substance consisting of atoms of the same atomic number. historically defined as a substance that cannot be separated into simpler substances by chemical means
atoms
the smallest representative particle of an element
property
a characteristic that gives a sample of matter its unique identity
molecule
a chemical combination of two or more atoms
gas
matter that has no fixed volume or shape; it conforms to the volume and shape of its container
liquid
matter that has distinct volume, but no specific shape
solid
matter that has both a definite shape and a definite volume
states of matter
the three forms that matter can assume: solid, liquid, and gas
pure substance
matter that has a fixed composition and distinct properties
compound
a substance composed of two or more elements united chemically in definite proportions
law of constant composition
a law that states that the elemental composition of a pure compound is always the same, regardless of its source; aka law of definite proportions
law of definite proportions
a law that states that the elemental composition of a pure compound is always the same, regardless of its source; aka law of constant composition
mixture
a combination of two or more substances in which each substance retains its own chemical identity
solution
a mixture of substance that has a uniform composition; a homogeneous mixture
physical properties
properties that can be measured without changing the composition of a substance, for example, color and freezing point
chemical properties
properties that describe a substance’s composition and its reactivity; how that substance reacts or changes into other substances
physical changes
changes (such as a phase change) that occur with no change in chemical compostion
changes of state
transformations of matter from one state to a different
chemical reactions
processes in which one or more substances are converted into other substances; also called chemical changes
intensive properties
a property that is independent of the amount of material considered, for example, density
extensive properties
a property that depends on the amount of material considered; for example, mass or volume
scientific method
the general process of advancing scientific knowledge by making experimental observations and by formulating hypotheses, theories, and laws
scientific law
a concise verbal statement or mathematical equation that summarizes a wide range of observations and experiences
hypothesis
a tentative explanation of a series of observations or of a natural law
theory
a tested model or explanation that satisfactorily accounts for a certain set of phenomena
SI units
the preferred metric units for use in science
mass
a measure of the the amount of material in an object. it measures the resistance of an object to being moved. in SI units, mass is measured in kilograms
Kelvin scale
the absolute temperature scale; the SI unit for temperature is the kelvin. zero on the kelvin scale corresponds to -237.15*C
Celsius scale
a temperature scale on which water freezes at 0* and boils at 100* at sea level
density
the ration of an object’s mass to its volume
precision
the closeness of agreement among several measurements of the same quantity; the reproducibility of a measurement
accuracy
a measure of how closely individual measurements agree with correct value
significant figures
the digits that indicate the precision with which a measurement is made; all digits of a measure quantity are significant, including the last digit, which is uncertain
dimensional analysis
a method of problem solving in which units are carried through all calculations. dimensional analysis ensures that the final answer of a calculation has the desired units
conversion factors
a ratio relating the same quantity it two systems of units that is used to convert the units of measurement
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