Chapter 1 Chemical Foundations

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Chapter 1 Chemical Foundations

• AP Chemistry

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Goals 1 9

• Differentiate between the term theory and law.
• Differentiate between physical and chemical
  properties.
• Differentiate between physical and chemical
  changes.
• Understand uncertainty in measurement.
• Determine significant figures from measurements
  and apply these values in calculations.
• Explain the difference between accuracy and
  precision.
• Explain the difference between random error and
  systematic error.
• Use dimensional analysis to convert between
  different units of measure.
• Classify matter as an element, compound, or
  mixture.

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What is Chemistry?

• Study of the structure, properties, and
  composition of matter, and the changes that
  substances undergo
• Study of matter and change

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How is Chemistry Done?

• The Scientific Method
• Making observations (collecting data)
• Making a prediction (hypothesis)
• Doing experiments to test the prediction

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Scientific Method Leads to

• Theory - model attempting to explain natural
  phenomena
• Natural law summary of observed behavior
• TWO VERY DIFFERENT OUTCOMES!

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How are Observations Made?

• Qualitative Observations descriptive,
  nonnumerical results
• EX blue, hot, large
• Quantitative Observations numerical observation
  including a scale
• EX 1.0 m, 100 K

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Units of Measurement

• Fundamental SI Units (know the prefixes on p. 9)

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Precision vs. Accuracy

• Accuracy agreement of a value with the true
  value
• Precision degree of agreement among several
  measurements of the same quantity

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Types of Error

• Random error measurement has an equal
  probability to be high or low
• Systematic error measurement is always either
  high or low

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Uncertainty in Measurement

• Every Measurement has some degree of uncertainty
• Uncertainty is accounted for by always recording
  certain digits and the first uncertain digit
• These numbers are called significant figures

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How are Significant Figures Determined?

• Nonzero integers are always significant
• Zeros
• Leading zeros are never significant
• Captive zeros are always significant
• Trailing zeros are significant if the number
  contains a decimal point
• Exact numbers are infinitely significant
• Seek handout for additional practice

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Significant Figures in Calculations

• Multiplication or Division
• The number of significant figures in the result
  is the same as the number in the least precise
  measurement used in the calculation
• Addition or Subtraction
• The result has the same number of decimal places
  as the least precise measurement in the
  calculation

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Dimensional Analysis

• Method used to convert from one unit to another
• Steps
• Use the equivalence statement that relates the
  two units
• Derive the appropriate unit factor to cancel the
  unwanted units
• Multiply the quantity to be converted by the unit
  factor to give the quantity with the desired units

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Classification of Matter

• Matter anything occupying space and having mass
• States of Matter solid, liquid, gas

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Mixtures

• Variable composition
• Homogeneous visibly indistinguishable parts
  (solution)
• Heterogeneous visibly distinguishable parts

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Separating Mixtures

• Mixtures can be separated into pure substances
  using physical changes
• Physical change change in form, not chemical
  composition
• Pure substance constant composition (elements
  and compounds)

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Separating Compounds

• Compound substance with constant composition
  that can be broken down into elements by chemical
  processes
• Chemical change change resulting in a new
  substance