Measurement
I.
Measurement
A. A quantity that has both a number and a unit
1. Which is a measurement?
i. 12 cm
ii. 134.54
iii. 0.0034
II. The Metric System
A. Standard units of measurement (SI)
Quantity
Length
Unit
meter
Symbol
m
Mass
Temperature
Time
Amount of
substance
kilogram
Kelvin
second
mole
kg
K
s
mol
B. Temperature conversion: °C + 273 = Kelvin
III. Metric Prefixes
Prefix
Kilo (k)
Centi (c)
Milli (m)
Micro (μ)
Nano (n)
Meaning
1000 times larger than the unit
100 times smaller than the unit
1000 times smaller than the unit
1 million times smaller than the unit
1 billion times smaller than the unit
Factor
103
10−2
10−3
10−6
10−9
IV. Scientific Notation
A. Used to write really big and small numbers
6.02 ×1023
B. The coefficient is equal to or greater than 1
and less than 10
C. The exponent is a positive or negative integer
V. Writing Scientific
Notation
A. For large numbers—
1. move the decimal to the left until one digit
remains in front
2. Count the number of times the decimal moves
3. The exponent is positive
4. Example:
i. 3,000  3 103
ii. 405,000  4.05 105
B. For small numbers—
1. move the decimal to the right until
one digit is in front
2. Count the number of times the
decimal moves
3. The exponent is negative
4. Example:
i. 0.00034  3.4 10−4
ii. 0.0000005070  4.05 10−6
VI. Accuracy
A. How close a measurement comes to the
actual value of whatever is measured
B. The more # of significant digits, the more
accurate the value
VII. Precision
A. How close a series of measurements are to
one another or “repeatability”
B. You must compare two or more
measurements to each other
VIII. Accuracy vs Precision
A. Example: Jack has a height of 70
inches. Which sets of measurements
are
1. Accurate and precise
2. Precise but not accurate
3. Neither precise nor accurate
i. 69.5 in., 70.5 in., 70.1 in.
ii. 45.3 in., 62.1 in., 84.3 in
iii. 78.3 in., 78.0 in., 78.1 in
IX. Percent Error
A. To find out how close you are to an
accepted or actual value
error
B. Percent error =  exp val – act val
act val

x 100%
C. Example: Your data reads 99.1g but the
accepted value is 101.0g, what is your percent
error?
Percent error = 99.1g − 101.0g
101.0g
%error = 1.88%
× 100