Chemistry Reference
In-Depth Information
significant digit. There will be times when you get a number like 500, and
you will want to show three significant digits. What options do you have for
reporting 500 as having three significant digits? Look at the following.
Methods for Showing “Ambiguous” Zeros in the Number 500 as
Significant Digits
Method
Example
1.
Use scientific notation to
show the zeros to the right of
both a decimal and a
significant digit.
1.
If we show the number 500 as
5.00 x 10
2
, the value of the
number is the same, but the
zeros are significant because
of Rule 3 on page 53.
2.
Place a decimal after the last
zero to show that you actually
consider the last zero
significant.
2.
If we show the number as 500.
we will consider all three
digits significant.
3.
Place a bar over the last zero
to indicate that the digit is
significant.
3.
If we show the number as 500
people will consider all three
digits significant.
When we do calculations in science, we must round properly and ac-
cording to the rules of significant digits. We will follow one rule when add-
ing and subtracting and another when multiplying and dividing. These two
important rules are shown here.
Rule for addition and subtraction: When adding or subtracting,
our answer must show the same number of decimal places as
the measurement in the problem with the least number of
decimal places.
Rule for multiplication and division: When multiplying or dividing,
our answer must show the same number of significant digits as
the measurement in the problem with the least number of
significant digits.
Let us return to our problem with the volume of the wood block and see
how we would apply the rules of rounding. (See Figure 2-4b on page 55.)
