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.

observationinvolves a judgment

or assumption

uses the fivesenses

inference

Data

Observations are also called data.

There are two types of data.

qualitative data quantitative 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 meters45 grams

4.3 km0.003 kg5.4 mL

Conversion Factor is a RATIO a/b or a bformed 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 5.712 grams in milligrams and kilograms

• Given = 5.712 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:

• 5.712 g x (1000mg) = 5712 mg

1 g

• Given grams and want kg, so the conversion factor should be written as follows:

• 5.712 g x ( 1 kg ) = 0.005712 kg

1000 g

Express 16.45 m in centimeters and kilometers

• 1645 cm

• 0.01645 km

Express 0.014 mg in grams

• 0.000014 g

Complete p 42

• 1 - 6

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