Chemistry
is the study of matter and the changes that matter undergoes.
Matter
is the physical material of the universe; it is anything that has mass and occupies space. It is also comprised of combinations of many elements.
Property
is any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types.
Atoms
the almost infinitesimally small building blocks of matter.
Molecules
two or more atoms are joined in specific in specific shapes.
States of Matter
gas, a liquid, or a solid.
Gas
has to fixed volume or shape; rather, it uniformly fills its container.
Liquid
has a distinct volume independent of its container and assumes the shape of the portion of the container it occupies.
Solid
has both a definite shape and a definite volume.
Pure Substance
is matter that has distinct properties and a composition that does not vary from sample to sample.
Elements
are substances that cannot be decomposed into simpler substances. On a molecular level, they are made up of one kind of atom. They make up matter.
Compounds
Substances composed of two or more elements; they contain two or more atoms.
Mixtures
are combinations of two or more substances in which each substance retains its chemical identity.
Law of constant composition (or Law of definite proportions)
the observation that the elemental composition of a compound is always the same
Physical Properties
can be observed without changing the identity and composition of the substance. Ex- color, odor, density, melting point, boiling point, hardness, etc.
Chemical Properties
describe the way a substance may change, or react, to form other substances. Ex- flammability
Intensive properties
do not depend on the amount of sample being examined and are particularly useful in chemistry because many of these properties can be used to identify substances.
Extensive properties
depends on the amount of sample, with two examples being mass and volume.
Physical Change
a substance changes its appearance but not its composition. It is the same substance before and after the change.
Chemical Change (or Chemical Reaction)
a substance is transformed into a totally different substance. It is not the same substance before and after the change.
Distillation
separating the components of a homogeneous mixture. This process depends on the different abilities of substances to form gases.
Metric system
units used for scientific measurements.
Mass
is a measurement of the amount of material in an object.
Temperature
a measure of hotness or coldness of an object, is a physical property that determines the direction of heat flow.
Celsius scale
based on the assignment of 0 degrees being the freezing point of water and 100 degrees being the boiling point of water.
Kelvin scale
the SI unit temperature scale.
Absolute zero
it is the lowest attainable temperature on the Kelvin scale.
Derived unit
is obtained by multiplication or division of one or more based units.
Precision
a measure of how closely individual measurements agree with one another.
accuracy
refers to how closely individual measurements agree with the correct, or "true," value.
Significant figures
in a measured quantity include one estimated digit, the last digit of measurement. It indicates the extent of the uncertainty of the measurement.
Dimensional analysis
helps ensure that solutions to problems yield the proper units.
Conversion factor
a fraction whose numerator and denomination are the same quantity expressed in different units.
