CHAPTER 3 OUTLINE
SCIENTIFIC MEASUREMENT
I. The Importance of Measurement
A. Qualitative and quantitative measurements
1. Qualitative -- descriptive data
a. Individual observation
2. Quantitative -- numerical data
b. Definite, use instrument correctly
B. Scientific Notation (6.02 X 1023)
1. Alias = Exponential notation
2. Numbers are written as products of two numbers
a. Coefficient
b. 10n
3. Coefficient is always between one & ten
4. Exponent (n)
a. Positive number is > 10
1. Multiply by 10 n times (move decimal right)
b. Negative number is < 10
1. Divide by 10 n times (move decimal left)
5. Multiplication and Division
a. Multiply coefficients, add exponents
b. Divide coefficients, subtract exponents
6. Addition and Subtraction
a. Adjust exponents to be the same, then perform operation
II. Uncertainty in Measurements
A. Accuracy, Precision, and Error
1. Accuracy -- how close a measurement comes to actual value
2. Precision -- how close a series of measurements are to each other
3. Error -- difference between accepted value and experimental value
4. Percent Error -- the relative error of the experimental value
B. Significant Figures (Digits) in Measurements
1. Sig. Fig. -- all known digits and one estimated digit
2. Rules to count sig. figs.
a. All nonzero digits (1-9) are significant
Ex. 24.2 3 sig. figs.
b. Zeros between nonzero digits are significant (sandwich rule)
Ex. 707 3 sig. figs.
c. Zeros to left of nonzero digits are not significant
Ex. 0.0097 2 sig. figs.
d. Zeros at end of the number and after a decimal are significant
Ex. 11.90 4 sig. figs.
e. Zero at end of the number and before an assumed decimal are not significant
Ex. 440 2 sig. figs.
440. 3 sig. figs.
f. Unlimited when counting or exact defined quantities
C. Significant Figures in Calculations
1. Rounding - answers cannot be more precise than the least precise measurement
2. Addition and Subtraction
a. Rounding is based on location of decimal point
Ex. 123.45 + 98.7 = 222.15 = 222.2 (since the second # is only to the tenths position)
3. Multiplication and Division
a. Rounding is based on smallest # of digits
Ex. 123.45 X 98.7 = 12184.515 = 12200 (since the second # has 3 sig. figs.)
III. International System of Units
A. Units of Length
1. Adopted internationally in 1960
2. SI (Le Systeme International d-Unites - France)
3. Base unit - Meter (m)
4. Change size of base unit with prefixes
B. Units of Volume
1. Derived unit - Liter (L)
a. Meter cubed (m3)
b. 1 L = 1 dm3 and 1 mL = 1 cm3
C. Units of Mass
1. Base unit - Gram (g)
a. 1 g = mass of 1 cm3 (mL) of water at 4oC
IV. Density
A. Determining Density
1. Density -- the amount of mass in a given volume
D = m/v (g/cm3)
2. More dense objects sink, less dense objects float
3. Increase temperature, then increase volume, then decrease density
a. Exception = WATER!
B. Specific Gravity
1. Sp. Gr. -- comparison of a substance's density with density of a reference substance
a. No units
2. Hydrometer -- instrument used to measure specific gravity
V. Temperature
A. Measuring Temperature
1. Temperature -- measure (in degrees) of hot or cold
2. Heat transfers from hot objects to cold objects
B. Temperature Scales
1. Celsius Scale
a. Two references = freezing water (0oC), boiling water (100oC)
b. 100 equal divisions (degrees) between them
2. Kelvin Scale
a. Absolute scale (based on absolute zero)
1. Absolute zero = 0 K (-273oC)
2. Temperature at which all molecular motion stops
b. Freezing water = 273 K, boiling water = 373 K (same degree increments as Celsius)
3. Conversions
K = oC +273 oC = K - 273
oC = 5/9(oF - 32) oF = 9/5(oC) + 32
Outline based upon:
Matta, M. S., Staley, D. D., Waterman, E. L., & Wilbraham, A. C. (2000). Chemistry, Addison-Wesley. (5th ed.). Menlo Park, CA: Prentice Hall. pp. 51-75
