Chemistry - Exam 1 Terminology

chemistry

the study of the composition, properties, and interactions of matter

hypothesis

a tentative explanation of observations that acts as a guide for gathering and checking information

laws

summaries of a vast number of experimental observations that describe or predicts some facet of the natural world

theory

a general explanation for the manifestation and behavior of all nature

scientific law

a statement that summarizes an observable behavior

solids

anything which has particles that are packed close together and are fixed in position

liquids

anything which has particles that are closely packed but they have some ability to move around

gases

anything which has particles that move randomly and may bump into each other and the container

pure substance

a classification of matter that has a constant composition from one sample to another

mixture

a classification of matter whose composition may vary from one sample to another

elements

a classification of pure substances that cannot be broken down into simpler substances by chemical changes

compounds

a classification of pure substances that are comprised of two or more elements; can be broken down (decomposed) to yield elements, other compounds, or both

homogeneous mixtures

a mixture that exhibits a uniform composition and appears visually the same throughout

heterogeneous mixtures

a mixture with a composition that varies from point to point

atom

the smallest particle of an element that has the properties of that element and can enter a chemical combination

molecules

two or more atoms joined by strong forces called chemical bonds

physical changes

changes that alter the state or appearance of the matter without altering the composition; ex: boiling/condensing, melting/freezing, subliming, dissolving 

chemical changes

changes that alter the composition of the matter; ex: rusting, burning, processes that release energy, fermentation

extensive property

a category of the properties of matter where the property depends on the amount of matter present; ex: mass and volume

intensive property

a category of the properties of matter where the property of a sample of matter does not depend on the amount of matter present; ex: temperature, density

physical properties

a characteristic of matter that is not associated with a change in its chemical composition; characteristics that are directly observable; ex: density, color, hardness, melting point, boiling point

chemical properties

the ability or inability of an object to change from one type of matter into another; describes behavior of matter; ex: flammability, toxicity, acidity

energy

the capacity to do work

work

the action of a force applied across a distance

kinetic energy

energy of motion

potential energy

energy stored in matter

sublime

direct change from solid to gas without becoming water in between

volume

the measure of the amount of space occupied by an object

density

the ratio of the mass of a sample of the substance to its volume (mass/volume)

accuracy

a measurement is said to be this if it yields a result that is very close to the true or accepted value

precision

a measurement is said to be this if it yields very similar results when repeated in the same matter