The Study of Change

1
The Study of Change

• Throughout recorded history, people have combined
  and heated materials to cause changes. From
  cooking, folk medicine, wood craft and smelting
  to the esoteric art of alchemy grew an interest
  in the systematic study of matter. The arts
  developed over a millennium and spanning from
  India to the Muslim world to Europe evolved into
  modern chemistry by the 17th century.
• Modern chemistry pursues practical applications
  in energy research, in medicine such as
  pharmaceuticals, in agriculture such as
  fertilizers and pesticides, in food science such
  as preservatives and other additives, and in the
  development of engineering materials such as
  alloys, plastics, ceramics, coatings, adhesives
  and lubricants. Our advanced understanding of
  the property and behavior of materials draws from
  the science of chemistry.

2
The Branches of Chemistry

• Inorganic chemistry is concerned with matter that
  is not carbon-based.
• Organic chemistry is concerned with carbon-based
  compounds.
• Physical chemistry is concerned with the
  mechanism, kinetics and thermodynamics of
  chemical reactions.
• Analytical chemistry is concerned with methods
  for the determination of chemical composition.
• Biochemistry is concerned with the chemical
  processes of life.

3
The Methods of Science

• The classical Scientific Method starts with a
  prediction (hypothesis) which is then tested in
  experiments, the results of which are analyzed to
  determine if the prediction is supported.
  Scientific laws are general statements of
  consistent observation, while scientific theories
  are explanations that may only be supported by
  observations, never proven absolutely.
• Scientific research may take either a deductive
  or inductive approach. The deductive approach,
  like the classical Scientific Method, starts with
  a prediction which is tested to determine its
  validity. The inductive approach starts with
  observations, from which consistent patterns may
  be concluded.

4
The Classification of Matter

• Mixtures are samples of matter that can be
  separated by physical means (e.g., filtration,
  evaporation, distillation, extraction,
  centrifugation, recrystallization,
  chromatography). Homogenous mixtures (i.e.,
  solutions) have a more consistent composition at
  the molecular level (e.g., sugar in water) in
  liquid solvents, they are typically transparent
  (clear). Heterogeneous mixtures are much less
  consistent (e.g., mud), while colloids are
  intermediate between those extremes (e.g., milk,
  mayonnaise, gelatin, whipped cream).
• (Pure) substances cannot be separated by physical
  means. They include elements, samples of which
  have atoms with the same number of protons,
  though they may have different numbers of
  neutrons (isotopes) or different modes of bonding
  (allotropes). Compounds have more than one type
  of element present, and are bound together as
  charged particles (ionic compounds), or
  exclusively by bonds where electrons are shared
  between atoms (molecular compounds).

5
The Properties of Matter

• Chemical properties concern how a material reacts
  chemically, changing its bonding to make new
  substances. Examples of such changes include
  cooking, burning, rotting, rusting, corroding,
  exploding, decomposing and putrefying, but do not
  include changes in physical state.
• Physical properties are all other properties
  which do not involve the change in composition.
  Common examples are color, density, physical
  state, heat conductivity, electrical
  conductivity, morphology, boiling point, melting
  point, hardness, malleability and ductility.
• Extrinsic properties only concern the amount of
  the material they are limited to the quantity of
  particles, mass and volume. Intrinsic properties
  are independent of the amount of material, and
  include all physical and chemical properties of
  matter.

6
The International System of Units

• The fundamental measurements in the International
  System of Units (i.e., the SI system) are meters
  of length, kilograms of mass, seconds of time,
  amperes of electrical current, kelvin of
  temperature, moles of chemical particle quantity,
  and candela of luminosity.
• Relative measurement levels in the SI system are
  distinguished as powers of ten (i.e., orders of
  magnitude) using metric system prefixes. Some of
  the more common prefixes are Tera (1012), Giga
  (109), Mega (106), kilo (103), deci (10-1), centi
  (10-2), milli (10-3), micro (10-6), nano (10-9)
  and pico (10-12).

7
Numbers in Science

• In science, numerical quantities communicate
  precision in that the lowest position is
  considered to be estimated, and the rest are
  considered repeatable on the device from which
  they were measured and from calculations done to
  obtain them. We refer to these places as
  significant figures. Scientific notation shows
  all of them, while in standard notation it is not
  as obvious.
• All positions from the first non-zero digit to
  the last non-zero digit are significant. Any
  further zeros to the right of the last non-zero
  digit which are also to the right of the decimal
  are also significant places.
• Products and quotients are limited in precision
  by the least precise of the quantities from which
  they are calculated. Sums and difference, in
  contrast, are rounded to the lowest common
  significant place among the quantities added or
  subtracted.
• Precision measures the repeatability of
  measurements, while accuracy is a measure of how
  closely measurements come to an accepted value.

8
Density and Temperature

• Density is the ratio of the mass of a substance
  to the volume it occupies. It is typically
  indicated in g/cm3 for solids, g/mL for liquids,
  and g/L for gases.
• Temperature is a measure of the average kinetic
  energy of the particles of matter in a sample.
  The Kelvin temperature scale is the accepted
  standard in science it is based on a lowest
  possible temperature, absolute zero or 0 K, at
  which all atomic motion ceases. There are some
  situations in science where it is still accepted
  to use degrees Celsius for temperature changes,
  as Celsius degrees are the same in magnitude, it
  only requires adding 273 to the Celsius to get
  the Kelvin temperature. The Fahrenheit scale is
  still in general use in the U.S. Conversion
  between Fahrenheit and Celsius scales are as
  follows
• F 1.8 C 32 C (F 32) / 1.8

9
Dimensional Analysis

• Dimensional Analysis (also called factor label or
  unit factor method) is a standard, accepted
  method for carrying out and communicating
  calculations which are accomplished purely from
  multiplication and division (i.e., no powers,
  logarithms, addition, subtraction, etc).
• In the technique, factors are placed side by side
  for multiplication, in such a way that the
  desired factors remain in the numerator and
  denominator, and all undesired factors cancel
  each other as a dimension in the numerator is
  divided and cancelled by its equivalent in the
  denominator. For example
• (tons) 1 ton x 1 lb x 1.03 g
  x 1 mL x 1.5 x 1021 L
• 2000 lb 454 g 1 mL
  10-3 L 1
• (Chang 10th Ed., page 35, problem 1.71)