Chemistry: Measurements and Calculations

what is an observation?

how we look at things in science

qualitative

describes the qualities of something (taste, color, sound)

quantitative

observations that are quantified (they have numbers, always measurements)

hypothesis

a possible explanation for an observation

law

a summary of repeatable observed behavior

theory

set of tested hypotheses that gives an overall explanation

mass

the amount of matter

length

the distance between 2 points

volume

the amount of 3D space something takes up

dimentional analysis

process of converting between units

conversion factor

a ratio made from 2 equivalent units

accuracy

closeness to actual value

precision

closeness that measurements are to eachother

significant digits

all the digits known with certainty, with one uncertain digit

1st rule for sig figs

any non-zero digits are ALWAYS significant

BEGINNING rule for 0’s

never significant (0.0001)

BETWEEN rule for 0’s

always significant (101)

END rule for 0’s

significant ONLY if the number contains a decimal point (100 vs. 100.)