Basic Chemistry Concepts

Science Ð'ÐŽV the study of the universe

Chemistry Ð'ÐŽV the study of matter and its changes

Scientific disciplines (ex. Chemistry, geology, physics, botany)

Subdisciplines (general, inorganic, organic, analytical, physical, environmental)

Technology: the application of scientific knowledge to the production of new products to improve human survival, comfort, and quality of life

Scientific Method

1. ask a question

2. observation (collect data)

3. hypothesis (educated guess)

4. experimentation

5. analyze results

6. conclusion

7. communicate your results

Hypothesis Ð'ÐŽV specific yet tentative guess

Theory Ð'ÐŽV less tentative; hypothesis that has been tested repeatedly

Precision vs. Accuracy

Precision: how close a series of measurements on the same object are to each other

Accuracy: how close a measurement comes to a true or accepted value

Uncertainty in measurements (in any measurement, the last digit reflects the uncertainty)

Significant digits

Ð'Ñ"Ð"Ñ› All non zero digits (1-9) always significant

Ð'Ñ"Ð"Ñ› Leading zeros (placeholders) not significant

Ð'Ñ"Ð"Ñ› Trailing zeros only significant when there is a decimal point.

Rounding Ð'ÐŽV Odd/even/5 Rule Ð'ÐŽV

Look at the number before the 5 and round to the nearest even number.

Operational Rules Ð'ÐŽV Significant digits

1. Multiplication and Division Ð'ÐŽV use fewest number of sig figs in the problem

2. Addition and Subtraction Ð'ÐŽV round to the place of greatest uncertainty

When doing a problem with only multiplication/division Ð'ÐŽV round answer at the end.

If you are doing combination of mult./div. and addition/subtraction,

round answer before switching types of operations!

Metric System (S.I. system) based on Ð'ÐŽÐ'§10Ð'ÐŽÐ'Ё

Composed of base units and prefixes

Base units Length Ð'ÐŽV meter

Mass Ð'ÐŽV gram

Area Ð'ÐŽV m2

Volume Ð'ÐŽV m3 or Liters

Prefixes Kilo (k) -- 103

Centi (c) -- 10-2

Milli (m) -- 10-3

Nano (n) -- 10-9

Be careful! Units do multiply and divide by each other.

When you cube a unit, it is the entire unit to the third power. ex. (2.54cm)3 = (2.54)3 cm3

Conversion factors- make sure they are in a 1:1 ratio of 2 equivalent units

DonÐ'ÐŽÐ'¦t be afraid of unusual conversion factors. If a problem says that 2 books are equal to a pound, then 2 books = 1 pound and your conversion factor is 2 books/ 1 pound.

Density = Mass per unit volume

Expressed as g/cm3 or g/mL

Percent Error formula

% error = absolute value of (measured value- accepted value) x 100

accepted value

10% error or less is an acceptable value of % error.

Temperature - a measure of the average kinetic energy of the particles in an object