PRECISION
PreLab Questions
 Label the place value names in the following measurement (the â€œonesâ€ and â€œtenthsâ€ columns have been labeled for you):
563.123 g 


ones 
tenths 


 In each of the following measurements, circle the digit that was estimated.
 9.468 g
 2.71 x 10^{3 }mol
 When making a measurement using the centimeter ruler shown below, the estimated digit should be written in which decimal place?
 Anytime a measurement is written, the precision of the equipment is apparent to the reader. Match measurements (a), (b) and (c) to the glassware scale you believe was used to make the measurement. Write the letter of the measurement (a, b or c) underneath the correct scale.
 Read the following measurements to the correct number of significant figures. Remember to include units.
 25 mL
 25.1 mL
 25.12 mL
30 
20 
26 
25 
20 
30 
 Balance read in grams_____________________________________________
 Thermometer read in degrees celcius ________________________________________
 Graduated cylinder read in milliliters_______________________________________
Name: ______________________________Date: ________________ Section: ____________
PRECISION
Data, Results and Observations
A. Investigating the Precision of Glassware, Part I
250 mL Beaker 
100 mL Graduated Cylinder 
10 mL Graduated Cylinder 

Mass of glassware, g 

Mass of glassware + H_{2}O, g 

Mass of H_{2}O, g (graph the value) 

Volume of H_{2}O, mL (graph the value) 
B. Investigating the Precision of Glassware, Part II
150 mL Beaker 
100 mL Graduated Cylinder 
10 mL Graduated Cylinder 

Initial volume, mL 

Final volume, mL 
C. Calculators and Measurements, Part I
100 mL Graduated Cylinder 
Show your work here: 

Initial water volume, mL 

Volume with 1 marble, mL 

Volume of 1 marble, mL 

Volume with 7 marbles, mL 

Volume of 7 marbles, mL 

Average volume of 1 marble. mL Do not round your calculatorâ€™s answer. 
D. Calculators and Measurements, Part II
100 mL Graduated Cylinder 
10 mL Graduated Cylinder 
Total 

Volume reading, mL 

Calculated volume 
Data Interpretation
1. Identify the decimal place (i.e. tens, ones, tenths, hundredths, etc.) and number of significant figures you should have for measurements for the volume and mass of water from Part A.
Decimal Place 
Significant Figures 

Volume measurement 
250 mL beaker 

Volume measurement 
100 mL cylinder 

Volume measurement 
10 mL cylinder 

Mass measurement 
Balance 
2. Compare the three sets of data represented by the lines on the class graph and answer the following questions.
 When you look at each line, what do you notice about the spacing of the points?
 How did the glassware used to make the measurements affect the outcome of the graphs?
 What does this tell you about the precision of the measurements for the different pieces of glassware?
 Rank the three pieces of glassware from highest to lowest amount of precision in their measurements.
 What is the relationship between accuracy and precision? Are you assured an accurate measurement if you use a more precise piece of glassware?
3. How did the precision of the glassware you used affect your ability to see the change in volume in â€œPart B. Investigating the Precision of Glassware, Part IIâ€?
4. If an experiment called for adding approximately 75 mL of acid to the reaction, which would be the appropriate piece of glassware to use? Why?
5. If an experiment called for adding 75.0 mL of acid to the reaction, which would be the appropriate piece of glassware to use? Why?
6. Examine your data and calculations for the determination of the volume of the marbles.
 How many significant figures should you have for your determination of the volume of 1 marble?
 How many significant figures should you have for your determination of the volume of a marble when using 7 marbles?
 What would you expect to happen to the significant figures for the volume if you had used 70 or 700 marbles? Why?
 Is the volume on your calculator display representative of the precision of the equipment used to make the measurements? Why or why not?
 Using the data you have for the total volume you calculated and the total volume you observed for â€œPart D. Calculators and Measurements, Part IIâ€, explain why the rule for significant figures in addition and subtraction is to keep the same number of decimal places as the number that originally had the fewest number of decimal places. HINT: Think about the level of precision you have with each piece of glassware.