Transcript Sig Figs

Sig Figs
• Significant figure a digit that is reliably known.
• Ex: 6.2 has 2 sig figs. The hundredth place is not
reliably known and, thus, not reported.
• The easiest way to determine sig figs in a number is
to write the number in scientific notation.
• 0.00620 = 6.20 x 10-3
• The trailing zero is reliably known, so it is
SIGNIFICANT.
• The number of significant figures is the number of
digits when written in sci notation.
Some Rules for Sig Figs
• The number of sig figs does not equal the number of
decimal places.
• In whole numbers, trailing zeroes are not sig figs.
Ex: 320,000 is 3.2 x 105
It has 2 sig figs.
• Changing units may shift the decimal points but it
doesn’t change the number of sig figs.
• When multiplying/dividing (or taking roots), the
number of sig figs in the answer should match the
number of sig figs of the least precise number in the
calculation.
• When adding/subtracting, the number of sig figs in
the answer should match the smallest amount of
decimal places of any number in the calculation.
• It’s fine to keep extra numbers around in the
intermediate steps, but your final answer MUST be
accurate in terms of significant figures.
• Otherwise, you’ve performed magic and have
something more accurate that we can verify.
Example
• The volume of a piece of Al is 4.44 x 10-4 m3. Given
a density of 2.7 x103 kg/m3, what is the total mass of
the piece of Al? (mass = density x volume)
m= 4.44 x 10-4 m3 (2.7 x103 kg/m3)
m= 1.199 kg
m= 1.2 kg
• If we have a second mass of Al, measured to be 6.47
kg, how much total Al do we have?
`
6.47 kg + 1.2 kg
= 7.7 kg