Transcript Notes 3

Chapter 3: Scientific
Measurement
3.1: Measurements and
Their Uncertainty
I. Types of Measures
• A. Qualitative: descriptive data, non-numerical
– Ex. Color, smell, feel of something
• B. Quantitative: definite data in number form
– Ex. Temperature in degrees
Write down two qualitative and two quantitative
measurements you could make about your own hand.
II. Scientific Notation Review
• Try These:
680 =
70.75 =
0.0063 =
III. Using your Calculator
•
•
•
A. To perform calculations
using scientific notation,
you need to use the EE,
EXP, or x10x button.
B. For 3.5x103, you type
3.5E3
Do not multiply by 10!
IV. Accuracy, Precision, Error
• A. Accuracy: how close measurement is to actual
value
• B. Precision: how close measurements are to each
other (consistency)
• C. Error: Numerical difference between accepted
and experimental value
• D. Percent error: (error/accepted value) x 100
V. Are They Accurate or Precise?
Precise
Neither
Accurate/Precise
VI. Uncertainty in Measurements
• A. Measurements always have some amount of
uncertainty based on the measuring device
4.36 cm
• B. Correct
measurements
always have
only one
“estimated
digit”
VII. Significant Figures
•
•
A. Numbers that tell us important information
B. Rules:
1. All non-zero #’s
[0.005468]
2. Zeros between non-zero
[202000]
3. Zeros behind numbers
[202.000]
(if any decimal is visible)
4. Exactly defined #’s have infinite sig. figs. (ex. 60
minutes in a hour)
VIII. Examples
• Identify which of the numbers in the following
values are significant.
2.5000
3000
205
100.0
0.00300
10.
IX. Sig. Figs. In Calculations
• A. Addition/ Subtraction: round answer to least
number of decimals in problem
Ex. 12.52 + 1.2 = 13.72 rounded to 13.7
• B. Multiplication/ Division: round answer to least
number of sig. figs in problem
Ex. 10.5 x 5.5 = 57.75 rounded to 58
X. Examples
• Solve the following using significant figures.
4.5 + 3.31 =
5.00 – 2 =
10.0 x 2 =
15.00 ÷ 3.0 =
3.2 International
System of Units
I. Units of
• A. SI: International System of
Units, metric, based on multiples
of 10
• B. Prefixes indicate size of
measurement
• C. Kilo: 1000, Centi: 1/100,
Milli: 1/1000
• D. Length: distance, measured in
meters (m)
II. Units of
• A. Volume: space occupied by matter
• B. Measured in Liters (L) or Meters3 (m3)
• C. Meters3 used when calculating volume by length
x width x height
III. Units of
• A. Mass: amount of
matter, grams (g)
• B. Weight: force of
gravity on mass
IV. Units of Temperature
• A. Definition: degree of hotness or
coldness
• B. Temp. Scales
– I. Celsius (ºC): freezing pt. water at
0°C, boiling pt. at 100°C
– II. Kelvin (K): 273 degrees more than
Celsius, set by absolute zero (-273°C)
– III. Kelvin = Celsius + 273
Galileo
Thermometer
V. Units of Energy
• A. Energy: capacity to do work or produce heat
• B. Units are calories (cal) or Joules (J)
1 cal = 4.184 J
Food Calories are actually
kilocalories (1000x bigger)!
3.3 Conversion Problems
I. Conversion Factors
• A. Ratio of equal measurements
Ex. 12 inches = 1 foot,
60 seconds = 1 minute
• B. In metric system one
measurement will usually be
“root” (meter, gram, liter, etc.)
other will have prefix
1 meter = 100 centimeters
II. Unit Cancellation (“Cross Method”)
•
•
•
•
•
•
•
1. Make cross
2. Given info. on top left
3. Desired unit at end of cross
4. Starting unit in bottom right (to cancel)
5. Corresponding unit on top right
6. Enter numbers to make conversion factor
7. Multiply #’s on top, divide on bottom
III. Example
• Convert 3.75 yards to inches.
IV. Complex Units
•
•
•
•
A. Ratio units (Miles/hour, gram/ml)
B. Need to change one or both units
C. Use bottom of cross for denominator unit
D. Ex. 20 miles/hour  miles/minute
20 miles
hour
1
hour
60 minute
= 0.3 miles/minute
V. Example
• Convert 10.0 kilometers/hour  meters/second.
3.4: Density
Floating in the Dead Sea
I. Determining Density
• A. Density: mass/volume
• B. SI units are gram/centimeter3 or
gram/milliliter
• C. Density increases as temp.
decreases
•D. Water is
exception, ice
less dense than
liquid water