Lecture 28/31/05 Review Appendix A

 No quiz this Friday (Quiz 1 due by end of the day Wed.) Quizzes mostly on homework problems Don’t need to memorize constants/equations Do need to know units and prefixes  Student solution manual at library  Reading ahead is recommended

Physically separable into Chemically separable into Combine chemically to form

UNITS

PREFIXES

Significant Digits  Rule 1 Count digits left to right starting from first non-zero digit  Rule 2 (Addition/Subtraction) # decimal places in the answer equal to the # of decimal places in the number with the fewest places  Rule 3 (Multiplication/Division) # sig. digits same as the number with the least number of sig. digits  Rule 4 Round up the last sig. digit if following digit ≥ 5  Hauri Corollary No points off if reasonable

Scientific Notation  Review p. 30 (K&T)  vs. 1 x 10 -3

Precision vs. Accuracy  Precision: How close replicates are to each other. Precision shown by standard deviation  Accuracy: How close measurements are to real answer.

What would good accuracy and poor precision look like?

Precision and Accuracy (cont.)  Precision shown by standard deviation

Percent error  For accuracy, what is ‘real’ answer?  Error = experimental value – accepted value

Physical Properties  Color  Temperature  State (solid, liquid, gas)  Melting point  Boiling Point  Density  Solubility  Conductivity  Malleability (How easy deformed)  Ductility (how easy drawn into wire)  Viscosity

Density  Pay attention to units Can do dimensional analysis  Oil vs. Water

Example problem: A piece of metal has a mass of g. If the density of silver is 10.5 g/cm 3, what is the volume of the metal?

A piece of copper has a mass of g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm 3 ). Example Problem

How dense is a person?