1. Measurement

2. Measurement A quantity that has both a number and a unit
Which is a measurement?
12 cm
134.54
0.0034

3. The Metric System Standard units of measurement (SI)
Temperature conversion:
Quantity
Unit
Symbol
Length
meter m
Mass
kilogram kg
Temperature
Kelvin K
Time
second s
Amount of substance
mole
mol
Converting temp; think about the alphabet
--C to K goes up in the alphabet, so add
--K to C goes down in the alphabet so subtract
°C = Kelvin

4. Metric Prefixes Prefix Meaning Factor Kilo (k) 103 Centi (c) 10−2
1000 times larger than the unit
103
Centi (c)
100 times smaller than the unit
10−2
Milli (m)
1000 times smaller than the unit
10−3
Micro (μ)
1 million times smaller than the unit
10−6
Nano (n)
1 billion times smaller than the unit
10−9

5. Scientific Notation Used to write really big and small numbers
6.02 ×1023
The coefficient is equal to or greater than 1 and less than 10
The exponent is a positive or negative integer
Circle and label coefficient

6. Writing Scientific Notation
For large numbers—
move the decimal to the left until one digit remains in front
Count the number of times the decimal moves
The exponent is positive
Example:
3,000  3 ×103
405,000  4.05 ×105
Underline large numbers, left, positive

7. For small numbers—
move the decimal to the right until one digit is in front
Count the number of times the decimal moves
The exponent is negative
Example:
 3.4 ×10−4
 4.05 ×10−6
Underline small numbers, right, negative

8. Accuracy
How close a measurement comes to the actual value of whatever is measured
The more # of significant digits, the more accurate the value

9. Precision
How close a series of measurements are to one another or “repeatability”
You must compare two or more measurements to each other

10. Accuracy vs Precision

11. Example: Jack has a height of 70 inches. Which sets of measurements are
Accurate and precise
Precise but not accurate
Neither precise nor accurate
69.5 in., 70.5 in., 70.1 in.
45.3 in., 62.1 in., 84.3 in
78.3 in., 78.0 in., 78.1 in

12. Percent Error
To find out how close you are to an accepted or actual value
Percent error =  exp val – act val  x 100%
act val
error
Point out the absolute value sign, we don’t care if we measured high or low

13. Example: Your data reads 99. 1g but the accepted value is 101
Example: Your data reads 99.1g but the accepted value is 101.0g, what is your percent error?
Percent error = 99.1g − 101.0g × 100
101.0g
%error = 1.88%
Point out the absolute value sign, we don’t care if we measured high or low