READING GRADUATED EQUIPMENT Read each digit that is certain, plus one digit that is uncertain To determine the certain digits, identify the most accurate graduations on the graduated equipment EX2-1 (of 15)
READING GRADUATED EQUIPMENT Read each digit that is certain, plus one digit that is uncertain To determine the certain digits, identify the most accurate.
Jan 13, 2016
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READING GRADUATED EQUIPMENT
Read each digit that is certain, plus one digit that is uncertain
To determine the certain digits, identify the most accurate graduations on the graduated equipment
EX2-1 (of 15)
Most Accurate Graduations:
One Celsius Degree
Uncertain Digit:
Tenths Place
Reading :
47.6 Cº
EX2-2 (of 15)
Most Accurate Graduations:
One Celsius Degree
Uncertain Digit:
Tenths Place
Reading :
42.0 Cº
EX2-3 (of 15)
Most Accurate Graduations:
One-Tenth of a Milliliter
Uncertain Digits:
Hundredths Place
Reading :
9.37 mL
EX2-4 (of 15)
Most Accurate Graduations:
One Milliliter
Uncertain Digits:
Tenths Place
Reading :
81.5 mL
EX2-5 (of 15)
Most Accurate Graduations:
One-Tenth of a Milliliter
Uncertain Digit:
Hundredths Place
Reading :
24.16 mL
EX2-6 (of 15)
ACCURACY
The extent to which a given measurement agrees with the standard value for that measurement
Accuracy is affected by experimenter error and the equipment used to make that measurement
EX2-7 (of 15)
6.81 cm
6.8 cm
EX2-8 (of 15)
TOLERANCE
For a graduated piece of equipment, it is the expected range of variation in a reading
Tolerances for many graduated pieces of equipment are provided by the manufacturer
5-mL Volumetric Pipet : 0.01 mL
When the tolerance is given, it is telling you the uncertain digit, and that will be that last decimal place recorded in the measurement
Reading for a 5-mL Volumetric Pipet : 5.00 mL
5.00 0.01 mL
EX2-9 (of 15)
To do this,
(1) Determine what the most accurate graduations represent on the glassware
(2) Divide the most accurate graduations by 2 to get the estimated tolerance of the graduated equipment
If the tolerance of a graduated piece of equipment is not given, it can be estimated.
EX2-10 (of 15)
Reading:
94.9ºC
Most Accurate Graduations :
1 Cº
Thermometer Tolerance:
1 Cº 2 = 0.5 Cº
94.9 0.5 ºC
EX2-11 (of 15)
Reading:
60.0 mL
Most Accurate Graduations :
1 mL
Graduated Cylinder Tolerance:
1 mL 2 = 0.5 mL
60.0 0.5 mL
EX2-12 (of 15)
PRECISION
The extent to which a series of measurements agrees with each other
Precision is affected by the experimenter
EX2-13 (of 15)
Density of Lead :
Trial 1 11.33 g/mL
Trial 2 11.34 g/mL
Trial 3 11.32 g/mL
Trial 4 11.16 g/mL
EX2-14 (of 15)
not precise
If an identifiable error caused the imprecision, the data can be ignored
If no identifiable error caused the imprecision, the data can be only be ignored by using a statistical test (such as a Q-test)
Density of Lead :
Trial 1 11.33 g/mL
Trial 2 11.34 g/mL
Trial 3 11.32 g/mL
Trial 4 11.16 g/mL
EX2-15 (of 15)
Q = gap _________
range
= 11.32 – 11.16 _________________
11.34 – 11.16
= 0.89
If Q > Q95%, then the data point can be ignored with 95% confidence
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