Chapters 1

1
Chapters 1 3

• Chemistry- A Study of the Properties and Changes
  of Matter

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Science vs. Chemistry

• Science- "knowledge attained through study or
  practice (Websters)
• Translation Systematic approach to determine the
  nature of the universe

• Chemistry- the study of the composition and
  changes undergone by materials
• Translation Using the scientific method to
  figure out what stuff is and what it can do

3
Chemistry Can Be

• Pure
• For the advancement of knowledge about our world

• Applied
• For a specific issue that faces society
• Pharmaceuticals, etc.

4
Scientific Method

• Question
• Hypothesis
• Experiment
• Results
• Conclusion
• Peer review
• Maybe,
• much, much later
• Theory

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Question

• After making observations of a phenomenon
• Generate a SPECIFIC question to investigate
• EX Why do apples turn brown if left out?

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Hypothesis

• After RESEARCH
• .is an EXPLANATION of the observations
• Followed by a specific prediction based on past
  experimental results or research
• Usually in the IF, THEN format
• EX Browning of apples is caused by heat
• Prediction If apples are allowed to reach a
  temperature of 20 degrees Celsius, then browning
  will occur

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Variables

• Independent variable controlled by experimenter
• If results are graphed, independent variable goes
  on the x axis (time is usually independent)
• Dependent variable depends on independent
  variable
• If graphed, results go on y axis

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Experiment

• Designed to INVESTIGATE THE HYPOTHESIS
• EX 10 apples are kept below 20 C
• 10 apples at 20 C
• 10 apples above 20 C

9
Results/Data Analysis

• Compile and LOOK FOR PATTERNS in experimental
  results
• Experimental results confirm or contradict
  predictions made on the basis of a hypothetical
  explanation
• EX 0 apples browned below 20 C, but 50 of
  apples above 20 C started browning within 24 hours

10
Conclusion

• Addresses whether or not the results SUPPORT or
  REFUTE the HYPOTHESIS
• Errors and future research are offered here
• EX The results show some support for the
  hypothesis in that half of the apples kept above
  20 C did brown. However,

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Peer Review

• After SEVERAL TRIALS and repeatable results
• Publish experiment in a scientific journal after
  peer review

12
Theory

• A theory is a well-supported hypothesis
• Formulated after EXTENSIVE, DIVERSE, AND RELIABLE
  data exists to support an explanation of a
  phenomenon
• Requires many years of research and support from
  many fields

13
Important Distinctions

• Qualitative- sensory observations (EX brown)
• Quantitative- numerical measurements (EX 5 lbs)
• Theory- Explains why for a given phenomenon
• Law- Describes a given phenomenon
• The Law of Gravity is that what goes up must come
  down.
• A Theory of Gravity would explain why this
  happens
• Observation- objective description of phenomena
• Inference- subjective explanation of phenomena

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Matter Classification

• Matter Flowchart
• Pure Substances
• Mixtures

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A. Matter Flowchart
MATTER
yes
no
Can it be physically separated?
Homogeneous Mixture (solution)
Heterogeneous Mixture
Compound
Element
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A. Matter Flowchart

• Examples
• graphite
• pepper
• sugar (sucrose)
• paint
• soda

• element
• hetero. mixture
• compound
• hetero. mixture
• solution

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B. Pure Substances

• Element
• composed of identical atoms
• EX copper wire, aluminum foil

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B. Pure Substances

• Compound
• composed of 2 or more elements in a fixed ratio
• properties differ from those of individual
  elements
• EX table salt (NaCl)

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B. Pure Substances

• For example

Two different compounds, each has a definite
composition.
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C. Mixtures

• Variable combination of 2 or more pure substances.

Heterogeneous
Homogeneous
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Tyndall Effect
Disperses Light
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C. Mixtures

• Solution
• homogeneous
• very small particles
• no Tyndall effect

• particles dont settle
• EX rubbing alcohol

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C. Mixtures

• Colloid
• heterogeneous
• medium-sized particles
• Tyndall effect
• particles dont settle
• EX milk

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C. Mixtures

• Suspension
• heterogeneous
• large particles
• Tyndall effect
• particles settle
• EX fresh-squeezed lemonade

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C. Mixtures

• Examples
• mayonnaise
• muddy water
• fog
• saltwater
• Italian salad dressing

• colloid
• suspension
• colloid
• solution
• suspension

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More Important Distinctions

• Intensive/extensive
• Material- specific type of matter
• Matter- has mass and takes up space (has property
  of inertia)
• Mass- amount of stuff in an object
• Weight- force of gravity of mass
• Mixture- composed of 2 or more substances
  physically combined
• Physical change- occurs without altering makeup
• Chemical change- occurs through alteration of
  substance
• Substance- purely 1 type of matter

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Separating Mixtures

• ALL MIXTURES CAN BE SEPARATED PHYSICALLY
• Filtration- used to separate a mixture with
  widely varying particle size
• EX rocks and water
• Distillation- used to separate a liquid mixture
• EX alcohol and water
• Crystallization- used to purify a solid
• EX impure aspirin can be dissolved and
  recrystallized from an alcohol/water solution
• Chromatography- separates a mixture based on
  polarity (affinity for stationary/mobile phase)

29
Substances

• Compounds can only be formed or broken down by
  chemical reactions
• Law of Conservation of Mass- mass can be neither
  be created nor destroyed in a chemical reaction
• Matter CAN change state

SOLID LIQUID GAS
Definite Shape YES NO NO
Definite Volume YES YES NO
Particle Spacing CLOSE CLOSE WIDE
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Laws of Compounds

• Law of Multiple Proportions
• If two compounds can result from the same
  element, the ratio will be in small whole numbers
• EX H2O vs H2O2

• Law of Definite Proportions
• Ratio of elements in a compound is constant
• EX H2O is always 16g of O for every 2g of H

• Percent by Mass
• mass (mass element/mass compound) 100
• O in H2O (16g/18g) 100 88.9

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Chemical and Physical changes

• A chemical change results in the formation of new
  stuff.
• Burning
• Rusting/Corrosion
• Decomposition
• A physical change does not make new stuff.
• Melting/freezing/boiling
• Crushing
• Dissolving

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The Periodic Table of Elements

• Elements are arranged by increasing atomic number
• Groups- vertical columns in the table that share
  chemical properties
• Periods- horizontal rows in the table that share
  the same principal energy level