Chemistry Lecture Notes January 8, 2006

Chemical Reaction: Is a Chemical CHANGE When something NEW is created. Reactants ---  Products A + B  C + D

The Scientific Method

An ordered and logical approach to solve a problem or answer a question.

Using the scientific method requires that one be a good observer. observation involves a judgment or assumption uses the five senses inference

Data Observations are also called data. There are two types of data. qualitative dataquantitative data measurements; must have numbers descriptions; no numbers

Parts of the Scientific Method Identify an unknown, question or problem. Make observations and formulate a hypothesis (a testable prediction). Experiment to test the hypothesis. Record Data Draw a valid conclusion.

A Scientific Experiment procedure the order of events in an experiment; the “recipe” Some experiments require a “control” and differ by only one variable. This is a controlled experiment. variable any factor that could influence the result The conclusion must be based on the data.

Measurements are quantities of matter and MUST ALWAYS include the appropriate units 76 meters 45 grams 4.3 km kg 5.4 mL

Conversion Factor is a RATIO a/b or a b formed by the EQUALITY between 2 different units.

Conversion factors are used to convert measurements or quantities from one unit to another.

4 quarters = 1 1 dollar 1 dollar = 1 4 quarters Why do these quantities both equal “1” ?

Because the ratio is equal to “1”, they can be multiplied by other factors in an equation WITHOUT changing the validity of the equation.

Dimensional Analysis

A mathmatical technique Solving problems involving quantities or measurements using ratios and equivalent units.

A mathmatical technique Solving problems involving quantities or measurements using ratios and equivalent units. Using conversion factors Conversion factors can be flipped (nominator for denominator) to find desired units.

Express a mass of grams in milligrams and kilograms Given = grams (? Sign.digits) What equality relates grams to milligrams? 1 g = 1000 mg This can be written as “ 1g/1000 mg or 1000 mg/1 g

Given grams and want mg, so the conversion factor should be written as follows: g x (1000mg) = 5712 mg 1 g

Given grams and want kg, so the conversion factor should be written as follows: g x ( 1 kg ) = kg 1000 g

Express m in centimeters and kilometers 1645 cm km

Express mg in grams g

Complete p

Recall Scientific Notation

Recall Significant Digits

P 77 Counting atoms Mole Avogadro’s number Molar mass Gram/mole conversions Conversions with avogadro’s number

P 219 Monatomic ions Binary ionic compounds Stock system for elements in d block Polyatomic ions Molecular compounds

P 237 Formula mass Molar mass Percentage composition Calculation of empirical formulas Calculation of molecular formulas

Review equations and reactions Balancing equations P 268 – 9 molar ratios Types of reactions Predicting products

Stoichiometry Ch 9

Gases Gas law