chemistry significant figures

all nonzero digits are significant

256 (3), 19,999 (5)

zeros to the left of the first non-zero are NOT significant

0.0274 (3)

zeros between nonzero are significant

1014 (4), 50.2 (3)

zeros at the end of a number that includes a decimal point are significant 

20.050 (5), 12.00 (4)

convey scientific notation

17,000 is a value that is not possible to know exactly how many digits are significant

-write 17,000 as 1.700 × 10⁴

addition and subtraction

-number of decimal places in the answer is equal to the number of decimal places for the value with the fewest significant digits after the decimal point 

ex: 0.203 (3 decimal places) + 1.8 (1 decimal place) + 10.94 (2 decimal places) = 12.9 (1 decimal place)

multiplication and division

-the number of sig figs in the answer is determined by the quantity with the fewest sig figs in the calculation

ex: 75 (2) × 0.05 (1) = 4 (1)