Chemistry Reference
In-Depth Information
Finding the Mass of a Sample of Water
?
Mass of empty
graduate = 53.925 g
Mass of just
the water?
Mass of full graduate = 64.025 g
Mass of the water =
mass of the full graduate - mass of the empty graduate
Mass of the water = 64.025 g - 53.925 g = 10.1 g
How interesting! Now, we have the exact opposite of the problem that we
encountered when we were calculating the volume of the wood block! Now,
we have measurements that are accurate to the thousandth place, but we
have an answer that is based on those measurements that only claims
accuracy to the tenth place. What do we do? We follow the rule for addition
and subtraction, and show an answer with as many decimal places as the
measurement with the least number of decimal places. Each of the
measurements show three digits past the decimal, so our answer becomes
10.100 g. Notice, we didn't change the value of the number, we simply
reported the correct degree of certainty.
Figure 2-4c
Now, try the following practice questions and check your answers at
the end of the chapter before moving on to the next lesson.
Lesson 2- 4 Review
1.
The number 40 shows _____ significant digit(s).
2.
The number 602 shows _____ significant digit(s).
3.
The number 0.000043 shows _____ significant digit(s).
4.
Complete the following calculation and round to the correct number
of significant digits.
3.21 g + 44.100 g + 21.0 g
