chem ch 1

chemistry

study of matter and the changes it undergoes

matter

anything that occupies space and has mass

substance

form of matter that has a definite composition and distinct properties

scientific method

systematic approach to research

hypothesis

tentative explanation for a set of observations

law

concise statement of a relationship between phenomena that is always the same under the same conditions

theory

unifying principle that explains a body of facts and/or those laws that are based on them

dalton’s atomic theory

All atoms of a given element are identical, having the same size, mass and chemical properties

element

Consists of only one kind of atom, cannot be broken down by physical of chemical methods

118

number of elements that have been identified

82

number of naturally occurring elements on earth

36

number of elements created by scientists

atomic num

1

chemical symbol

2

atomic mass

3

compound

substance composed of atoms of two or more elements chemically united in fixed proportions

chemical means

Compounds can only be separated into their pure components (elements) by ——— means

mixture

combination of two or more substances in which the substances retain their distinct identities

homogenous mixture

composition of the mixture is the same throughout

heterogenous mixture

composition is not uniform throughout

physical

——— means can be used to separate a mixture into its pure components

gas, liquid

solutes in gaseous solutions

gas, liquid, solid

solutes in liquid solutions

liquid, solid

solutes in solid solutions

physical

A ——— change does not alter the composition or identity of a substance

A ——— change alters the composition or identity of the substance(s) involved

extensive

An ——— property of a material depends upon how much matter is being considered

intensive

An ——— property of a material
does not depend upon how much
matter is being considered

mass

measure of the quantity of matter

weight

force that gravity exerts on an object

accuracy

how close a measurement is to the true value

precision

how close a set of measurements are to each other