Basic Chemistry Concepts
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Science ÐÐŽV the study of the universe
Chemistry ÐÐŽV 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
ask a question
observation (collect data)
hypothesis (educated guess)
experimentation
analyze results
conclusion
communicate your results
Hypothesis ÐÐŽV specific yet tentative guess
Theory ÐÐŽV 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
ÐєДћ
All non zero digits (1-9) always significant
ÐєДћ
Leading zeros (placeholders) not significant
ÐєДћ
Trailing zeros only significant when there is a decimal point.
Rounding ÐÐŽV Odd/even/5 Rule ÐÐŽV
Look at the number before the 5 and round to the nearest even number.
Operational Rules ÐÐŽV Significant digits
1. Multiplication and Division ÐÐŽV use fewest number of sig figs in the problem
2. Addition and Subtraction ÐÐŽV round to the place of greatest uncertainty
When doing a problem with only multiplication/division ÐÐŽV 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 ÐЎЧ10ÐÐŽÐÐ
Composed of base units and prefixes
Base units
Length ÐÐŽV meter
Mass ÐÐŽV gram
Area ÐÐŽV m2
Volume ÐÐŽV 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
DonÐЎЦt 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