Measuring
Accuracy v. Precision pg. 8
Precision - how closely the
measurements match each other.
Instruments that measure using
more decimals are more precise.
Accuracy – how closely the
measurement matches the true
or accepted value.
Accurate
Precise
 Accurate
 Precise
 Accurate
 Precise
 Accurate
 Precise
 Accurate
 Precise
How To Read Scientific Instruments
• 1) Record the _______ digit on the
instrument.
• 2) Then _______________
the last digit.
How to Count
Significant Figures
1. Count all of the digits you are sure of.
2. Add the last digit you estimate.
Percent Error
• When quantities have accepted or true
values, we can calculate the percent error
between our measurement of the value and
the accepted value with the formula
How to Read a Graduated Cylinder
• Sit the graduated cylinder on a level surface.
• Lower your eyes to the level of the liquid
(called the meniscus).
• Take your reading from the bottom of the
meniscus.
• Count all of the digits you are sure of.
• Add the last digit that you estimate.
Quiz
• Number your paper 1 to 15.
1) Measuring Length
A.
B.
C.
D.
2 cm
19 cm
1.95 cm
1.95238 cm
2) Measuring Length
A.
B.
C.
D.
10cm
1.1cm
1.05cm
1.526cm
3) Measuring Length
A.
B.
C.
D.
17 cm
17.5 cm
18.0 cm
17.5082 cm
4) Measuring Length
A.
B.
C.
D.
4cm
4.3cm
4.30cm
4.3057cm
5) Measuring Length
A.
B.
C.
D.
12 cm
12.0 cm
12.7 cm
12.0953 cm
6) Measuring Liquids
• The meniscus is the curve in the upper
surface of a liquid close to the surface of the
container or another object, caused by
surface tension. It can be either convex or
concave.
Is this meniscus convex or concave?
6) _________________
For questions 7 to 12, measure the amount of liquid in each
graduated cylinder by reading the bottom of the meniscus.
7) Measuring Liquid Volume
A.10ml
B.10.3ml
C. 11.5ml
D.13.0ml
8) Measuring Liquid Volume
A.
B.
C.
D.
266 ml
287 ml
290 ml
294 ml
9) Measuring Liquid Volume
A.52 ml
B.53 ml
C. 54.5 ml
D.52.8 ml
10) Measuring Liquid Volume
A.80 ml
B.80.0 ml
C. 81.0 ml
D.79.0 ml
11) Measuring Liquid Volume
A.2.8 ml
B.2.80 ml
C. 2.90 ml
D.2.9 ml
12) Measuring Liquid Volume
A.4.90 ml
B.4.80 ml
C. 5.0 ml
D.5.0853 ml
13) Measuring Solids
A.625.62g
B.26.57g
C.265.73
D.526.6g
14) Measuring Solids
A.373.33g
B.734.33g
C.374.33g
D.373.3g
15) Measuring Solids
A.222.50g
B.221.50g
C.221.5g
D.221.0g