Name: ________________________
Date: __________
Chemistry Test 2 Review - Accuracy and Precision, Significant Figures, Unit Conversions
Review the following bullets and answer the questions that follow to prepare for Test 2:
• Memorize the rules for determining significant figures listed and explained on textbook pages 17 & 18.
• A trick for determining significant figures:
(1) If a decimal is present then start counting at the first non-zero number from the left.
(2) If a decimal is absent, then start counting the first non-zero number from the right.
• (Textbook page 20) When multiplying or dividing numbers, the result must be rounded to the same number of
significant figures as the number used in the calculation with the least significant figures. For example: 2.6 ÷ 7 =
0.371429. The answer must be rounded to one significant figure: 0.4 because the divisor 7 had only one significant
figure while 2.6 had two significant figures.
• (Textbook page 21) When adding or subtracting numbers you must round the answer to the decimal place of the
number that was least precise that was added or subtracted. Examples:
• Accuracy is how good or close a measured value is to the actual value. Precision is how detailed the meaurement is
made (more significant figures). Measurements are precise when subsequent measurements come close to each other.
• (Textbook page 27) Unit conversion factors are used to change the units of a measurment from one unit to another.
They are ratios of equivalent measurments with different units. For example:
100 cm
1m
2.54 cm
1 in
60 s
1 min
1 day
24 hr
1
• (Textbook page 27) To convert one unit to another, start with the measurement to be converted and then apply the
conversion factor so that the beginning units cancel and the final unit remains. For example:
Convert 534 feet to meters. There are 3.28 feet in one meter.
534 ft
1m
534 m
sig figs
×
=
= 162.804878 m 

→ 163 m
1
3.28 ft
3.28
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____
1. Which of the following measurements has two significant figures?
a.
b.
23.0
0.230
c.
d.
2300
0.0230
Short Answer
2. Round off each of these measurements to three significant figures.
a) 98.473 L __________
b) 0.00076321 cg __________
c) 57.048 m __________
d) 12.17 oC __________
3. Using the rules for significant figures, round off each of the following answers correctly.
a) 8.7 g + 15.43 g + 19 g = 43.13 g __________
b) 853.2 L - 627.443 L = 225.757 L __________
c) 38.742 kg ÷ 0.421 = 92.02375 kg __________
d) 5.40 m × 3.21 m × 1.871 m = 32.431914 m3 __________
4. Determine the number of significant figures in each of the following.
a) 11 soccer players _____
b) 10,800 meters _____
c) 0.070020 meter _____
d) 5.00 cubic meters _____
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5. Use an example to explain the difference between precision and accuracy.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6. What conversion factor would be used to convert from feet to yards?
.
7. Convert 100 cm to mm using conversion factors.
.
8. A snail decided it wanted to see the country and take a trip across it. If the snail travels at a rate of 1m per
hour, how long would it take to travel across the country in years from Washting D.C. to San Francisco, CA
if the distance is 4529km? Use unit conversions to solve this problem.
.
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