Chemistry Reference
In-Depth Information
2.
A(n) _______________ measurement is close to the “true” or
accepted value.
3.
Explain how “estimation digits” are used in chemistry.
4.
Record the length of the ribbon shown in the figure below to the
proper digit.
1.0 cm
2.0 cm
5.
Record the length of the ribbon shown in the figure below to the
proper digit.
1.0 cm
2.0 cm
Lesson 2- 4: Calculating with Significant Digits
Imagine that you wanted to find the volume of a regularly shaped wooden
block in your chemistry lab. You measured the length, width, and height of
the block and found them to be 4.55 cm, 9.10 cm, and 2.54 cm respectively.
To find the volume of the block, you would multiply the three numbers
together, as shown in Figure 2-4a.
Calculating the Volume of a Wood Block
Given
Length = 4.55 cm
Width = 9.10 cm
Height = 2.54 cm
Volume = L × W × H
Volume = 4.55 cm × 9.10 cm × 2.54 cm
Volume = 105.1687 cm
3
Figure 2-4a
Do you see anything wrong with the reported answer to the calcula-
tion? Notice that each of the original measurements was only considered
accurate (including the estimation digit for each) to the hundredths place,
or 2 digits past the decimal. However, the reported answer suggests that it
is actually accurate to 4 digits past the decimal place. This doesn't make
