chemistry quest 1

chemistry

study of matter at the atomic level, including structure, properties, interactions with energy, and transformations

macroscopic

experiments and observations

submicroscopic

atoms and molecules

symbolic

chemical & math equations, graphs

matter

occupies space, has mass, composed of atoms

pure substance

has a definite composition and distinct properties (can be represented by chemical formula)

element

only one type of atom present

compound

more than one type of atom present

compound

two or more elements chemically united in fixed proportion, cannot be separated into simpler substances by physical processes, requires a chemical reaction to separate

mixture

physical combination of two or more substances (substances retain their individual identities)

extensive property

depends on amount of matter (mass, volume, energy)

intensive property

doesn’t depend on amount of matter (density)

pure substance

anything that has a pure composition

physical properties

can be studied without changing the identity of the substance, can be qualitative or quantitative

quantitative physical properties

can be extensive or intensive

physical change

state of matter changes, but identity doesn’t

chemical properties

revealed as it interacts with other substance through chemical reaction

chemical change

results in a change of composition (ex. original substance no longer exists)

plasma

exists at very high temperatures where atoms can ionize by losing electrons

SI unit of mass

kg

SI unit of length

meters

SI unit of time

seconds

exact numbers

either numbers which are part of a definition, or counted values

inexact numbers

numbers obtained by any method other than counting (ex. measuring with ruler)

random error

measured results can be above/below the “true” value with equal probability

systematic error

measured results show bias in one direction (often calibration error)

significant figures

the meaningful digits in a reported number

uncertain digit

the last digit in a measured number

precision

reproductability of a measurement

accuracy

proximity to the true value

thermal equilibrium

objects in thermal contact come to the same temperature via flow of heat

Fahrenheit/Celsius conversion equation

F = 9/5(C) +32

Celsius/Kelvin conversion equation

K = C + 273.15

energy

the capacity to do work

kinetic energy

associated with an object in motion

kinetic energy equation

K = 1/2mv² m = mass; v = velocity

potential energy

associated with position of an object in relation to external field of force. if released, the object starts to move

potential energy equation

PE = mgh m = mass; g = acceleration (9.81); h = height

conservation of energy

the total energy of a closed mechanical system is conserved during any process

law of definite proportions

a chemical compound always contains the same proportions of its elements by mass (allows us to compute mass percentage)

law of multiple proportions

if two elements can combine to form more than one compound with each other, the masses of one element that combine with a fixed mass of the other element are ratios of small whole numbers