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Chemistry I - Chapter 1 NotesChemistry and You

- Mr. Seaney

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

Table of Contents cont

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

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

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

Scientific Method Flow Chart

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

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

1-4 Units of Measurement

- The Metric System
- International System of units SI

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

Some Derived Units

Common Metric Prefixes

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

Accuracy vs. Precision

?

Precise Not Accurate

?

Accurate Not Precise

?

Not Accurate or Precise

?

Accurate And Precise

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

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

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.

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)

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

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!

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

Credits

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