1. Chapter 1: Introduction
Chemistry 1020: Interpretive chemistry
Andy Aspaas, Instructor

2. What is chemistry?
“The science that deals with the materials of the universe and the changes that these materials undergo.”
Chemistry in relation to other sciences

3. Chemistry around us
Advances from chemistry
Medicine
Agriculture
Energy
Plastics
Problems from chemistry?

4. Scientific problem solving
The scientific method: process behind all scientific inquiry
Flexible, changes when new information is learned
Start with a question, problem or observation
Hypothesis: possible explanation
Experimentation: controlled process of gathering new information
Observations, do they support the hypothesis?
Theory: a tested hypothesis, can still be revised

5. Law vs. theory
Natural law: generally observed behavior, result of measurements
Theory: our attempt to explain why certain behaviors happen
Scientific method is still limited by human imperfection

6. How to learn chemistry
Reading, vocabulary, memorization are only a start
Should be considered a minor part of your learning process in chemistry
Problem solving skills are even more important!
Why practice homework problems are assigned
Struggle with them, use answers carefully
Mistakes can be valuable

7. Chapter 2: Scientific Notation
Chemistry 1020: Interpretive chemistry
Andy Aspaas, Instructor

8. Types of observations
Observations are a key part of any type of scientific research
Qualitative: a description (a white solid was formed)
Quantitative: a specific measurement (the product weighs 1.43 grams)

9. Measurements and numbers
Measurements must contain both a number and a unit - without both, the measurement is meaningless
Many numbers in measurements are very large or very small
Distance from earth to sun: 93,000,000 miles
Width of an oxygen atom: meters
Is there an easier way to deal with such ungainly numbers?

10. Scientific notation
Used to make very large or very small numbers more manageable
Multiply a number between 1 and 10 by any power of 10
200 in scientific notation?
For even larger numbers, count the number of places the decimal point must move, and make that the power of 10
230,000,000,000 in scientific notation?

11. Scientific notation
Works with small numbers too
For small numbers, move the decimal point to the right, and use that as the negative power of 10
Left is positive, “LIP”
Using a calculator
The E or EE button on your scientific calculator

12. Units of measurement
Unit: which scale or standard is used for a particular measurement
English system: US residents are most familiar with
Metric system: used in most of the rest of the world
SI, or International System, used in scientific work
Based on metric system
Agreed upon by scientists worldwide

13. Some fundamental SI units
Quantity Name of unit Abbreviation
mass kilogram kg
length meter m
time second s
temperature kelvin K
• Most other SI units can be derived from these

14. Prefixes to SI units
Prefix Symbol Meaning Power of 10
mega M 1,000,
kilo k
deci d
milli m
micro µ
nano n

15. Length
Fundamental SI unit for length: meter
A little longer than a yard
Using prefixes as the power of 10
1 mm = 10-3 m = m
1 inch = 2.54 cm
Measured with a ruler or caliper

16. Volume
Amount of 3-dimensional space occupied by an object
Unit: liter (L)
1 L = 1 dm3 (cubic decimeter)
1 millileter (mL) = 1 cm3
Commonly used volume unit in chemistry
Volume measurements:
Graduated cylinder
Syringe
Buret

17. Mass
The specific amount of matter present in an object
Measured on a balance
Not to be confused with weight
(Force of gravity acting on the mass of an object)
Dependent on the strength of gravity
Earth vs. moon?
Measured on a scale
Mass used much more commonly in chemistry
SI fundamental unit: kilogram

18. Uncertainty in measurement
Analog measurements - measured mechanically against some type of physical scale
Estimate required for last digit of measurement
Last digit = the uncertain digit
Can be expressed as ± amount of the uncertain digit (4.542 ± 0.001)
Digital measurements - read from a display
Last digit still uncertain even though you don’t do an estimation

19. Accuracy vs. Precision
Accuracy: how close a single measurement or set of measurements are to their true value
Precision: how similar a number of measurements are
Dartboard example
Beaker of water example

20. Significant figures
Sum of all certain numbers in a measurement plus the first uncertain number
Indicates the amount of precision with which a measurement can be made
Since each measurement contains uncertainty, that uncertainty must be tracked when manipulating the measurements

21. How many sig figs does a measurement have?
Nonzero integers are always significant (1 thru 9)
Leading zeroes (on the left) are never significant
Captive zeroes are always significant
Trailing zeroes (at the end) are only significant if there’s a decimal point
Exact numbers (obtained by counting) have an infinite number of sig figs

22. Rounding off
Calculators don’t understand sig figs
Will return as many digits to you as possible
You must round the answer to the correct number of sig figs
Look at the digit to the right of the last sig fig
0-4, just drop it and everything to the right
5-9, increase last sig fig by one, drop rest
Look only at the one digit to the right of the last sig fig, ignore all others!

23. Determining sig figs in calculations
When multiplying or dividing, find the measurement with the smallest number of sig figs
Answer must be rounded to that many sig figs
When adding or subtracting, find the measurement with the smallest number of decimal places
Answer must be rounded to that many decimal places
Practice!

24. Dimensional analysis introduction
We do this all the time without even thinking about it
Example: planning a party
15 guests
3 drinks per guest
How many drinks should you buy?
Conversion factor: a ratio of two measurements with different units that are equal to each other
Expressed as a fraction, two possible orders!

25. Dimensional analysis calculations
Set up an equation like this
Known quantity x conversion factor = unknown quantity
Orient conversion factor so units of known quantity are cancelled
Multiply the known by the conversion factor
The only remaining unit should be the one you’re solving for
Correct for sig figs
Does the answer make sense?
Practice, practice, practice, practice, practice!

26. Temperature scales
Fahrenheit scale: used in the US
Celsius scale: used in most rest of world, and by most scientists
Kelvin scale: SI base unit of temperature
0 K is lowest possible theoretical temperature

27. Temperature scales Fahrenheit Celsius Kelvin Absolute zero -460 °F
Water freezes
32 °F
0 °C
273 K
Body temp
98.6 °F
37 °C
310 K
Water boils
212 °F
100 °C
373 K

28. Temperature conversions
Celsius to Kelvin
Temperature units are the same size
Zero points are different
TK = T°C + 273
Kelvin to Celsius
Solve above for T°C
T°C = TK - 273

29. Fahrenheit and Celsius
Different degree units and zero points
T°F = 1.80(T°C) + 32
T°C = (T°F - 32) / 1.80

30. Density
Density: amount of matter present in a given volume of substance
Density = mass / volume
Units could be kg/L, g/cm3, g/mL, etc.