Chemistry I Chapter 1 Notes Chemistry and You

1
Chemistry I - Chapter 1 NotesChemistry and You

• Mr. Seaney

2
Table of Contents

• 1-1 What is Chemistry?
• 1-2 The Scientific Method
• 1-3 Safety in the Laboratory
• 1-4 Units of Measurement
• 1-5 Uncertainty in Measurement
• Accuracy vs. Precision

3
Table of Contents cont

• 1-6 Working with Numbers
• 1-7 Problem Solving

4
1-1 What is Chemistry?

• The study of substances and changes they undergo
• Chemistry in action touches every aspect of
  life
• The central science underlies all other
  sciences
• The study of matter

5
1-2 The Scientific Method

• A way to answer questions and solve problems
• Steps in the Scientific Method
• Observation Curiosity about nature
• Question Why or how the event occurs
• Hypothesis Proposed or tentative answer
• Experiment Test with variable control
• Conclusion Analyze data interpret results
• Natural Law Explains how nature behaves
• Theory Explains why, allows prediction

6
Scientific Method Flow Chart
7
1-3 Safety in the Laboratory

• Rules Procedures
• Follow teachers and lab directions
• Notify teacher of problems
• Know how to use safety equipment
• Wear safety goggles at all times
• Tie back long hair
• Avoid awkward transfers
• Let hot stuff cool or use tongs / hot mitts
• Carry chemicals defensively
• Dispose of wastes properly
• Clean up after lab

8
Know Your Safety Symbols

• See text page 16 figure 1-12
• Memorize the equipment and symbols in your lab
  book for the test
• Review the video study guides on lab safety

9
1-4 Units of Measurement

• The Metric System
• International System of units SI

10
1-4 Measurement Continued

• Area and Volume Derived Units (combination of
  base units)
• cm2 or m2 - area cm3 or m3 - volume
  1dm31liter 1 cm31 ml

B. Be careful converting between units
11
Some Derived Units
12
Common Metric Prefixes
13
1-5 Uncertainty in Measurement

• Making Measurements
• All Measurements are uncertain
• Every measurement involves estimation
• This uncertainty can be expressed as x where x
  is one tenth of the smallest measure possible
  with that instrument
• Reliability in measurement
• Precision - Repeatability of measurement
• Accuracy - Nearness to accepted value

14
Accuracy vs. Precision
?
Precise Not Accurate
?
Accurate Not Precise
?
Not Accurate or Precise
?
Accurate And Precise
15
1-6 Working with Numbers

• Significant Digits
• Measurements are only as precise as the
  instrument
• Numbers must be rounded to the correct number of
  significant figures
• Atlantic Pacific Rule - If a decimal point is
  present count from the Pacific side starting with
  the first nonzero digit. If a decimal is absent
  count from the Atlantic side starting with the
  first nonzero digit

16
Rules for Significant Figures

• All zeros between nonzero digits are significant
  (count them)
• Zeros to the left of an expressed decimal and to
  the right of a nonzero digit are significant
  (count)
• Zeros to the right of an expressed decimal and
  left of a nonzero digit are not significant
  (dont count)
• Zeros to the right of nonzero digits that are
  right of the decimal are significant (count them)
  
• If there is no expressed decimal all zeros to the
  right of the last nonzero digit are not
  significant

17
Practice on Significant Figures
3000
.00105
3.006
1 3000
3 .00105
4 3.006
4020
4020
3 4020
.7000
4 .7000
80.007
80.007 5
.00091
2 .00091
50.
2 50.
18
1-6 cont

• II. Significant digits in Calculations
• A. When multiplying or dividing round to the
  least number of significant figures used in the
  operation
• Example 2 X 12 24 round to 20
• B. When adding and subtracting round to the
  fewest decimal places used
• Example 3.02 5.3 1.158 9.478 round to
  9.5
• C. Conversions and exact numbers (counting
  numbers) have infinite significant digits
• Example .0432 km X 1000 m/km 432 m
• D. If several operations are performed dont
  round until the final answer
• E.If the last number is ? 5 Round up or lt 5 round
  down
• III.Scientific Notation useful in working with
  very large or small numbers
• A. Make sure you can convert from and to
  scientific notation ( See worksheets and handout)

19
1-6 cont..

• IV. Percents and Percent Error
• A. Be able to convert to decimals decimals to
  
• B. Relative error (ER) is calculated by taking
  the observed value (O) minus the actual value (A)
  (this is absolute error (Ea)) and dividing by
  the actual value (A) then multiplying by 100.
• C. Relative error is a measure of accuracy

V. Ratios A. Ratios such as density and speed can
be used to greatly simplify calculations
20
1-7 Problem Solving

• Use dimensional analysis (factor labeling) to
  solve word problems
• Conversion factors should be used to cancel the
  units you dont want and leave behind the units
  you do want
• Always list the information you do know then read
  carefully to find out what you need to calculate.
  Set up the problem to solve for what you want to
  know. Check your answer to see if it is
  reasonable and in the correct units.
• Practice - Practice - Practice
• You must have this skill!

21
1-7 cont

• Graphing
• Label each axis with the variable and unit and
  give the graph a title
• Independent variable goes on the X axis Dependent
  variable on the Y axis
• Plot data points and connect with a best fit line
  (not dot to dot)
• Use the finished graph to establish relationships
  (directly proportional, inverse, logarithmic)
  between the variables

22
Credits

• Text - Prentice Hall Chemistry
• Microsoft Publishing Gallary
• More Power to YA class