Virginia State University

General Chemistry I

Chem 161Fall 2011

Dr. Victor Vilchiz

Alchemy

• What is it?

• Where did it originate?– Egypt… Khem = Turn Black– Greece… Cheo = to cast– China… Chin-I = gold making juice

• How did it lead to Chemistry?

AIR

• Ancient elements– How many?

• 1• 2• 3• 4

– 5 ?

• How many Elements do we have now?

AIR

• Fixed Air

• Explosive Air

• Noxious Air

• Flammable Air

Atomic Theory

• Who postulated it?

• How many postulates?

• What are they?

• How many are “correct”?

Atomic Bookkeeping

• Atoms– Molecules

• Formulas– Types of formulas

• Subscripts• Coefficients• Hydrates

• Chemical Reactions– Balancing Chemical Reactions.

General Chemistry IVirginia State University

Chapter 2

Dr. Vilchiz

Fall 2011

THE UNIVERSE

• According to Science how did it all started?– Evidence?

• Direct?

• Indirect?

Questions…

• How big can it get?

• How small was it?

• How much mass is there?

• Etc.

Measurements

• Types of Properties

• Types of Measurements

• Parts in a measurement

• Units– Basic vs derived– SI vs Imperial

SI UNITS

• The SI (Systeme Internationale) of units has six basic units– Length meter m– Temperature Kelvin K– Mass kilogram kg– Time second s– Luminous Intensity candela cd– Substance amount Mole mol

Derived Units

• The rest of the units are derived from these basic units.– Volume m3

– Force Newton N=kgm/s2

– Energy Joule J=kgm2/s2

– Pressure Pascal Pa=kg/ms2

– Velocity m/s– Density kg/m3

Metric System

Similar to Table 2.4 In your book

Temperature

• What is temperature?– What different scales do we use?

• Where did they come from?

Scientific Notation

• What is it?

• Why use it?

• What else does it accomplish?

• What practical benefits does it have?

Measurement and Sig Figs

All measurements, no matter how careful they are taken, have an error, uncertainty, associated with them.

Errors

• Type of errors?

• How can we “fixed” them?

• How do they affect reported numbers?

• Accuracy vs Precision

Rules for Sig Figs

• What numbers count?All nonzero digits are significant.

Zeros between significant figures are significant.

Zeros preceding the first nonzero digit are not significant.

Zeros to the right of the decimal after a nonzero digit are significant.

Zeros at the end of a nondecimal number may or may not be significant. (Use scientific notation.)

Significant Figures

3456 has 4 sig figs.

0.0486 has3 sig figs.

16.07 has

4 sig figs.

1.300 has 4 sig figs.

1310 has 3 sig figs.

1310. has

4 sig figs.

Significant Figures & Math

When multiplying and dividing measured quantities, give as many significant figures as the least found in the measurements used.

When adding or subtracting measured quantities, give the same number of decimals as the least found in the measurements used.

14.0 g /102.4 mL = 0.136718g/mL

Significant Figures

14.0 g /102.4 mL = 0.136718g/mL

only three significant figures

Significant Figures

14.0 g /102.4 mL = 0.137 g/mL

only three significant figures

Significant Figures

Exact Numbers

• What are they?

• Do they have sig figs?

• How do they affect calculations?

Calculations…

• Dimensional Analysis– Conversion Factors

• How accurate do I have to be?