Uncertainty and measurement
Name:_____________________Period:____
Paper clip patterns: Measure the length of a paper clip with each of the three rulers. The measurements will not
be identical. Write your answer in the space provided
Ruler letter
A
Length of paper clip (cm)
Questions:
1. Were all of your measurements identical? EXPLAIN
B
2. Which measurement are you most uncertain of (required the
greatest amount of estimation)?
C
Uncertainty in measurement
- Measurements are only as precise as the instrument used.
- Uncertainties of measurements are predictable and can be calculated.
- They can be estimated to be ____________________ of the smallest division on a
___________________.
- For a digital reading the ______________ digit is rounded up or down by the
instrument and so will also have a random error of +/- half of the last digit.
- The last # which you estimate is the _________________________.
Accurate-
Precise-
Trial 1
Trial 2
Trial 3
Average:
Student
2.5 cm
2.4 cm
2.3 cm
2.4cm
Student B
1.8cm
1.7cm
1.8cm
1.76cm
Measurements: Actual= 2.4 cm
1. Were either of the students accurate? Which one? why?
2. Were either of the students precise? Which one? why?
Percent error:
Example: Calculate the percent error of student
B’s average
Accepted value = actual, theoretical, true, known
UNITSThere are 3 systems: In chemistry we use the SI system, which is basically the same as the metric system
Measurement
Unit
abbreviation
Instrument
Picture
Mass-
Exponents review:
100 =
101 =
Weight-
102 =
103 =
10-1 =
10-2 =
10-3 =
Scientific notation (same as exponential notation)
It looks like:
N is a number between _____ and ________
If M is positive it’s a __________________
If M is negative it’s a ___________________
Ex. 1: The distance from the earth to the sun is
93,000,000 miles
Ex. 3: Convert 2.3 x 102 to standard notation
Ex. 4: 3.6 x 10-4 in to standard notation
Ex. 2 The diameter of an atom is 0.00000000562cm
Try these on your own:
1. convert 0.0000003 to scientific notation
3. convert 3.4 x 107 to standard notation
2. Convert 4,500000000 to scientific notation
4. Convert 2 x 10-3 to standard notation