Chapter 2

Scientific Method Click to return Home

Section 2-1 Click to return to Chemistry Page


 

Objectives

 

  1. Observing and Collecting Data
    1. observing- the use of the senses
    1. Qualitative measurement- describes the quality of a substance.
    2. Quantitative measurement- describes the substance using a numerical value.
    1. System- a specific portions of matter in a given region of space.
  1. Formulating Hypotheses- testable statement
  2. Testing Hypotheses-Requires experimentation
  3. Stages in the Scientific Method ( pg 31)

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  4. Theorizing-a broad generalization


Units of measurement

Sections 2-2

Objectives

  1. SI measurement
    1. Le Systeme International d’Unites
    2. Has seven base units
    3. Governed by the National Institute of Standards and Technology
  1. SI Base Units

Table 2-1 SI BASE UNITS

Quantity

Symbol

Name

Ab.

Defined Standard

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2-2 SI Prefixes

Prefix

Unit abbreviation

Exponential factor

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    1. Mass- the amount of matter in a given object
    1. measured by a balance
    2. compared to a standard set of masses
    1. Weight- is a measurement of gravitational pull on matter.
  1. Derived SI Units

Table 2-3 Derived SI units

Quantity

Symbol

Unit

Abb.

Derivation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    1. Volume- the amount of space occupied.
    2. Density- The ratio of mass to volume
    1. Density = Mass/ Volume
    2. Sample problem 2-1 pg. 39
  1. Conversion Factors- is a ratio derived from the equality between two different units that can be used to convert from one unit to the other.
    1. This is the most important math skill in chemistry.
    2. Commonly called FACTOR LABEL METHOD
    3. ALWAYS PUT A MULTIPLICATION SYMBOL AND LINE.
    4. Practice below Pg 41 sample problem 2-2

  


Section 2-3

Using Scientific Measurements

Objectives

    1. Accuracy and Precision
      1. Accuracy- how close one is to the answer
      2. Precision- refers to the range of the measurements. Do you constantly get the same answer?
      3. Percent Error- a measurement that states how good one’s answer is.

a. Percent error =

((Accepted value – Experimental value) ¸ Accepted Value) X 100%

b. Practice problem 2-3 page 45

    1. Significant Figures- in a measurement consists of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.
      1. What numbers are measured?
      2. What numbers are important?

Table 2-5 Rules for Determining Significant Zeros

Rule

Example

 

 

 

 

 

 

 

 

  1. Rounding- pg 48
  2. Addition or subtraction- answer must have the same number of decimal places as the number with the fewest decimal places.
  3. Multiplication and Division- Answer must have the same number of digits as the number with the fewest number of sig figs.
    1. Scientific notation- numbers written in the form M X 10 n
      1. 1 < M > 10
      2. n is some whole number
    1. Using Sample problems pg. 52
    2. Direct Proportions- when dividing one by the other produces a constant value
    3. 1. The variables will do the same

    4. Inverse proportions- when the product is constant.

1. The variables will do the opposite.