Chem: Units and Measurements

Quantitative

information that can be measured and expressed numerically (numbers, statistics)

Qualitative

information that is subjective and unique (color, observations)

Leading zeros

NEVER significant (0.000123 = 3 sig figs)

Captive zeros

ALWAYS significant (4,507,006,021 = 10 sig figs)

Trailing zeros

Significant if there is a decimal ANYWHERE in the number

Zero saying

“Left, never. Middle, sometimes. Right, is there a decimal?”

Conversion factors

have an infinite number of sig figs

Multiplication/division

answer is limited to the starting number with the LEAST number of total sig figs

Addition/subtraction

the answer is limited to the starting number after the decimal with the LEAST amount (care about decimal numbers, not sig figs)

Conversion factor

anything equal to itself (1 mile = 1.6km)

C to F

F = 1.8 x C + 32

C to K

K = C + 273

Density (g/mL)

Mass (g) / Volume (mL)