The Science of Chemistry

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Chapter 1

• The Science of Chemistry

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1.1 What is Chemistry?

• Why study chemistry?
• chemical any substance with a definite
  composition
• chemical reactions changes in chemicals

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1.1 What is Chemistry?

• Physical states of matter
• solid fixed volume and shape particles in a
  rigid structure
• liquid fixed volume but not shape particles
  slip past one another
• gas neither fixed volume nor shape particles
  move quickly

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Water in Different States
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1.1 What is Chemistry?

• Changes of matter
• Physical changes changes in which the identity
  of a substance does not change
• examples changes of state, dissolving, crushing,
  etc.

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1.1 What is Chemistry?

• Changes of matter, cont.
• Chemical changes changes in which the identity
  of substances change and new substances are
  formed
• represented by chemical equations

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1.1 What is Chemistry?

• Changes of matter, cont.
• Chemical changes, cont.
• reactants are consumed in a reaction
• products are formed in a reaction
• atoms are rearranged, but not created or destroyed

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1.1 What is Chemistry?

• Changes of matter, cont.
• Evidences of chemical change
• 1. Evolution of a gas
• 2. Formation of a precipitate
• 3. Release or absorption of energy
• 4. Color change in the reaction system

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1.2 Describing Matter

• Matter has mass and volume
• volume is the space an object occupies
• volume of solids
• volume of liquids
• volume of gases

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1.2 Describing Matter

• Matter, cont.
• mass is the quantity of matter in an object
• size is irrelevant
• mass is different than weight
• weight is the gravitational force acting on mass

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1.2 Describing Matter

• Units of measurement
• qualitative terms describe the quality of
  something
• examples
• quantitative terms describe the amount, or
  quantity of something
• examples

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1.2 Describing Matter

• Units of measurement, cont.
• quantities have units
• examples

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1.2 Describing Matter

• SI is the standard system of units
• there are 7 base units

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1.2 Describing Matter

• base units can be modified by prefixes to express
  very large or very small quantities

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Common SI Units
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1.2 Describing Matter

• measurements can be converted from one unit to
  another using conversion factors
• conversion factor ratio between two units that
  express the same quantity
• examples

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1.2 Describing Matter

• conversion factors, cont.
• solving
• 1. identify the quantity and unit given and the
  unit you want to convert to
• 2. place the conversion factor so the given unit
  cancels
• 3. multiply the given quantity by the conversion
  factor check your work

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1.2 Describing Matter

• conversion factors, cont.
• solving example

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1.2 Describing Matter

• SI, cont.
• some units are derived from the 7 base units for
  some reason, they are called derived units
• examples

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1.2 Describing Matter

• Properties of matter
• physical property property that can be determine
  w/o changing the nature of the substance
• examples melting point, density
• density is the ratio of mass to volume Dm/V
• example

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Density of Aluminum
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Densities of Various Substances
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1.2 Describing Matter

• Properties of matter, cont.
• chemical property property that describes what
  happens when matter reacts with other kinds of
  matter involves chemical change
• example oxidation

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1.3 How is Matter Classified?

• Pure Substances
• pure substances can by identified by
  characteristic physical or chemical properties
• elements are pure substances
• some exist as single atoms (e.g., helium) called
  monatomic
• some exist as molecules (e.g., O2, H2, N2,
  halogens) called diatomic

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Element Names, Symbols, and Symbols Origins
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1.3 How is Matter Classified?

• Pure Substances, cont.
• some elements have more than one form (e.g.,
  oxygen, carbon) called allotropes

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1.3 How is Matter Classified?

• Pure Substances, cont.
• Compounds are pure substances
• compounds are made of more than one kind of atom
• compounds are represented by formulas (e.g.,
  H2O2, H2O, C3H6O)
• structural formula shows how atoms are connected
• ball-and-stick model shows 3D relationships
  between atoms

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1.3 How is Matter Classified?

• Pure Substances, cont.
• space-filling model shows relative sizes of
  atoms (as well as position)

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1.3 How is Matter Classified?

• Mixtures
• mixture sample of matter with two or more pure
  substances NOT chemically combined
• mixtures can vary in composition and properties
• examples air, drinks, alloys (mixtures of metals)

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1.3 How is Matter Classified?

• Mixtures, cont.
• homogeneous mixture uniform distribution of
  substances
• examples
• heterogeneous mixture uneven distribution of
  substances
• examples

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Examples of Mixtures
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1.3 How is Matter Classified?

• Mixtures, cont.
• distinguishing mixtures from compounds
• properties of a mixture reflect properties of its
  components (not true with compounds)
• a mixtures components can vary in proportions,
  but a compound has a definite composition