1. No category

Name_____________________________________
Period _____
Date _________
ACCURACY & PRECISION
Idea 1: Measurements (3.25 cm) are different than other numbers (3.14159265).
 Measurements represent an action by someone with some measuring instrument.
 Measurements have built-in uncertainty; no measurement is exact.
 Measurements have units.
Idea 2: The uncertainty in a measurement needs to be communicated.
Definitions:
1. accuracy – how close a measurement is to _______________________________
2. precision of measurement – ___________________________________________
3. precision of instrument - _____________________________________________
Precision Problems:
Several lab groups measure the density of aluminum. Here is their data:
Team 1
Team 2
3
2.65 g/cm
Team 3
3
2.75 g/cm
Team 4
3
2.80 g/cm
Team 5
3
2.77 g/cm
Team 6
3
2.60 g/cm
Team 7
3
2.65 g/cm
2.68 g/cm3
4. What is the average density? ________g/cm3
5. Subtract the highest value from the lowest value: _________ This is the range of values.
6. Divide the range number by 2: _______
7. The precision of the measurement can be shown as _____________ g/cm3.
8. Here is more data. Is this more precise, less precise, or the same precision as the above data? ____________
Team 1
Team 2
Team 3
Team 4
Team 5
Team 6
Team 7
2.60 g/cm3
2.70 g/cm3
2.80 g/cm3
2.75 g/cm3
2.65 g/cm3
2.62 g/cm3
2.78 g/cm3
9. Each of five students used the same ruler to measure the length of the same pencil. These data resulted: 15.33
cm, 15.34 cm, 15.33 cm, 15.33 cm, 15.34 cm. The actual length of the pencil was 15.85 cm. Describe
whether accuracy and precision are each good or poor for these measurements.
Make measurements use the pictures on the right.
Show the correct number of significant figures.
10. ________________ Temperature in oC (close up of thermometer)
11. ________________ Volume in mL (graduated cylinder)
12. ________________ Length of line in cm (ruler)
Use the following information to answer questions 13 to 17.
A chemistry student wants to measure the mass of a test tube he is planning to use in lab. There are two balances
in the room - Balance A and Balance B. Balance A is marked to the nearest 0.1 g and Balance B is marked to the
nearest 0.01 g.
13. Which balance is the more precise instrument?
The student recorded the following data:
Balance A
Balance B
Trial 1
3.12 g
3.431 g
Trial 2
3.17 g
3.552 g
Trial 3
3.13 g
3.348 g
14. Average
15. Range
16. Which balance had the most precise measurements?
17. If the true mass of the test tube is 3.14 g, which balance was the most accurate?
18. ________________ Volume in mL delivered from a buret. Final volume - initial volume = volume delivered.