1. Unit 1 Chemistry & You

2. Chemistry – the study of the composition of matter (the stuff things are made of) and the changes that matter undergoes
You undergo and perform chemical reactions (rxns) everyday (breathing, eating, cooking.)
You benefit from the work of chemists everyday (plastic ballpoint pen, microwave oven, post-it notes, ice cream, etc.)

3. The Scientific Method Observation Hypothesis Experiment Theory
Example: Flashlight

4. Theories vs. Laws Everyday use of: Scientific Definition of :
Theory: abstract thought untested in practice; an assumption or guess1
Law: A rule established by authority, society or custom1
Scientific Definition of :
Theory: inferred explanation of some aspect of the natural world. Theories do not become laws even with additional evidence [or time]; they explain laws. However, not all scientific laws have accompanying explanatory theories.2
Law: a general description about how some aspect of the natural world behaves under stated circumstance(s).3  often in equation form
Explain – to offer reasons for
Describe – to give a verbal account of

5. Measurement Qualitative: results in descriptions (Gray Cats)
Quantitative: results in numerical form (23 Cats)
SI System – International System that’s used to standardize quantities.
Why is this important?
There are 7 base units from which all other units are derived (made)
Base units - meter and second
Derived unit (of speed) - meter per second

6. Quantity it represents
7 Base Units
Unit Name
Unit Symbol
Quantity it represents
*Kilogram kg
Mass
*Meter m
Length
*Second s
Time
*Mole
mol
Count, quantity
*Kelvin K
Temperature
Candela cd
Luminous intensity
Ampere A
Electric current

7. Kilogram (kg) mass
measure of the quantity of matter; amount of material in an object
Never changes
(Weight – force due to the pull of gravity on an object; mass times acceleration  it can change)
Do you weigh more at the top of a mountain, or at sea-level?

8. Meter (m) length Second (s) time Line segment connecting two points
Volume = derived  m3 (Liter (L) is metric unit)
1 L = 1 dm3 = 1000 cm3 = 1000 mL
Second (s) time
Interval between 2 occurrences

9. Kelvin (K) temperature
Measure of the average kinetic energy of particles that make up a sample
K = oC

10. Uncertainty in Measurement
Measurements are uncertain
Measuring instruments are never completely flawless
Measuring always involves some estimation
Why is using a millimeter or centimeter stick to measure a ladybug better than using a meter stick?
Accuracy: how close measurement is to true value
depends on care in measuring
Precision: how close several measurements are to the same value (reproducibility)
depends on estimation and number of divisions on instrument

11. How would you describe the following sets of numbers?
68.6, 68.7, 68.9  Aim = 23
Precise but inaccurate
40.002, ,  Aim = 40
Precise and accurate
2.4, 6.0, 7.0  Aim = 4
Imprecise and inaccurate
0.874, 0.87,  Aim = 0.87
Imprecise but accurate

12. Scientific Notation
Used to make math with very large or very small numbers easier
Numbers in sci.not. look like:
M x 10n  4.0 x 102 = 400
3.23 x 10-3 =
where M is a number 1-9 and n is an integer that tells you how many places the decimal has been moved. If n is negative, the number is less than one.
M is the coefficient, n is the exponent

13. Multiplying Numbers in Scientific Notation
To Multiply:
Multiply coefficients, add exponents
(2.0 x 10^3) x (3.0 x 10 ^4)
(2.0 x 3.0) x 10^3+4
6.0 x 10^7 13

14. Dividing Numbers in Scientific Notation
To Divide:
Divide coefficients, subtract exponents
(8.0 x 10^5) / (4.0 x 10 ^2)
(8.0/4.0) x10^5-2
2.0 x 10^3 14

15. Adding and Subtracting Numbers in Scientific Notation
To Add or Subtract:
1. Must make exponents the same
make # smaller OR move decimal to the left, exponent increases
make # larger OR move decimal to the right, exponent decreases
2. Then add or subtract coefficient and exponent remains the same 15

16. Dimensional Analysis & Factor – Label Method
Dimensional analysis is a technique used to convert between units cmm
Factor –Label method is the use of conversion factors with their labels to reach a desired quantity when doing a calculation
Ex. Conversion factor 1 min = 60 s
17.0 min (60 s/1 min) = 1020 s

17. Significant Digits/Figures
Used to tell how accurate your measurements and calculations are
Sig. figs. contain all the certain digits and 1 estimated digit of measurement.
Not all zeros are significant
ex ,
Atlantic – Pacific rule helps to identify sig.figs.: If a decimal is Present, count from the Pacific; If the decimal is Absent, count from the Atlantic A P

18. Rounding with Significant Figures
Decide how many sig. figs. the answer should have, then round to that many digits counting from the left
Sample problem 3-2 p. 59

19. Addition and Subtraction with Significant Figures
Answer should be rounded to the same number of decimal places (not digits) as the measurement with the least number of decimal places
Sample problem 3-3 p. 60

20. Multiplication and Division with Significant Figures
Answer should be rounded to the same number of significant figures as the measurement with the least number of significant figures
Sample problem 3-4 p. 61

21. Density
Definition: The mass per unit volume of an object
Equation:

22. Percent Error % error = measured value – accepted value x 100%
Used to compare a measurement to its accepted value
If answer is negative, data is lower than expected. If answer is positive, data is higher than expected.

23. Sources 1. American Heritage Dictionary
2. NSTA Position Statements: The Nature of Science
3.Teaching about Evolution and the Nature of Science