Chemistry Reference
In-Depth Information
5.
Complete the following calculation and round to the correct number
of significant digits.
2.34 cm × 0.21 cm × 32.4 cm
6.
Which of the following shows the number 500 with 3 significant digits?
a) 500
b) 500.
c) 5.0 × 10
2
d) 5 × 10
3
7. Which measurement shows a total of four significant digits?
a) 0.005 g
b) 4.0 x 10
4
g
c) 3204 g
d) 5400 g
8.
How many significant digits should the answer to the calculation
below show?
4.99 m × 4.0 m
a) 1 b) 2 c) 3 d) 4
9. What is the correct answer, including significant digits, to the
following calculation?
3.42 cm + 2.3 cm + 33.4 cm
a) 39 cm b) 39.1 cm c) 39.12 cm d) 40 cm
10. What is the correct answer, including significant digits, to the
following calculation?
2.755 cm × 5.0 cm
a) 14 cm
2
b) 13.8 cm
2
c) 13.78 cm
2
d) 13.775 cm
2
Lesson 2-5: The Factor-Label Method
Unit conversion is such an important part of working with numbers in
science that it becomes necessary for us to learn how to make these conver-
sions in a neat and organized fashion. The factor-label method, which is also
called dimensional analysis, is designed to do exactly that. Some students
find the method intimidating and hard to learn at first, but developing the
ability to use it is certainly well worth the effort. Not only will the factor-
label method save you a great deal of time in the long run, but it will also
improve your grade by preventing you from making careless errors in your
calculations.
Let's suppose we asked two different students to convert 4.75 years
into seconds. The workspace of a student who doesn't use the factor-label
method might look like the space shown below.
