Matter

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Matter
Chemistry I Chapter 2
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What is Chemistry?

• Textbook Definition The science of matter and
  the changes it undergoes.
• Dictionary Definition The science of the
  composition, structure, properties, and reactions
  of matter, especially of atomic and molecular
  systems.

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Chemistry

• The central science Why?
• Because most of the phenomena that occur in the
  world involve chemical changes

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What is Matter?

• the material of the universe
• has mass and volume
• mass the amount of matter in an object
• volume the amount of space an object takes up

5
The Nature of Matter
Gold
Mercury

• Chemists are interested in the nature of matter
  and how this is related to its atoms and
  molecules.

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Chemistry Matter

• We can explore the MACROSCOPIC world what we
  can see
• to understand the PARTICULATE (MICROSCOPIC)
  worlds we cannot see.
• We write SYMBOLS to describe these worlds.

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A Chemists View of Water
Macroscopic
H2O (gas, liquid, solid)
Symbolic
Particulate
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A Chemists View
Macroscopic
2 H2(g) O2 (g) --gt 2 H2O(g)
Particulate
Symbolic
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The Macroscopic View

• The states of matter
• Solids
• Liquids
• Gases
• Plasma

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Kinetic Nature of Matter

• Matter consists of atoms and molecules in
  constant random motion.

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STATES OF MATTER

• Solids have rigid shape, fixed volume. External
  shape can reflect the atomic and molecular
  arrangement.
• Reasonably well understood.
• Liquids have no fixed shape and may not fill a
  container completely.
• Not well understood.
• Gases expand to fill their container.
• Good theoretical understanding.

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OTHER STATES OF MATTER

• PLASMA an electrically charged gas Example
  the sun or any other star

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Gas Liquid Solid
low density high density high density
fills container completely does not expand to fill container - has definite volume rigidly retains its volume
assumes shape of container assumes shape of container retains own shape
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The Particulate Nature of Matter

• All matter is made up of atoms
• Elements consist of atoms of the same type
• H, He, Cs, Ru, Fe, O
• Compounds are formed when atoms chemically bond
  to one another in a specific way
• CO, H2O, NaBr, C6H12O6

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Properties of Matter

• Physical vs. Chemical Properties
• physical property - characteristic of a substance
  that can be observed without changing the
  substances identity
• chemical property - characteristic of a substance
  that can only be observed if the identity of the
  substance is changed

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Physical Properties

• What are some physical properties?
• color
• melting and boiling point
• odor

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ChemicalProperties

• What are some chemical properties?
• Flammability
• Reactivity with water
• If it tarnishes

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Physical vs. Chemical Properties

• physical
• chemical
• physical
• physical
• chemical

• Examples
• melting point
• flammable
• density
• magnetic
• tarnishes in air

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Changes of Matter

• Physical vs. Chemical Changes
• physical change - change in one or more physical
  properties, but does not affect the composition
  of a substance
• chemical change - change in the composition of a
  substance, in which a substance becomes a new
  substance (aka, a chemical reaction)

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Physical Changes

• Some physical changes would be
• boiling of a liquid
• melting of a solid
• dissolving a solid in a liquid to give a
  homogeneous mixture a SOLUTION.

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Chemical Changes

• Some chemical changes would be
• Hydrogen and oxygen combining to form water
• Silver tarnishing
• Baking a cake
• Any chemical reaction!

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Chemical Changes

• Burning hydrogen (H2) in oxygen (O2) gives H2O.

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Sure Signs of a Chemical Change

• Heat
• Light
• Gas Produced (not from boiling!)
• Precipitate a solid formed by mixing two
  liquids together

http//jchemed.chem.wisc.edu/JCESoft/CCA/CCA0/MOVI
ES/S1047.MOV
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Physical vs. Chemical Changes

• Examples
• rusting iron
• dissolving in water
• burning a log
• melting ice
• grinding spices

• chemical
• physical
• chemical
• physical
• physical

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Classifying Matter

• pure substances (elements and compounds) always
  have the same composition
• mixtures (heterogeneous and homogeneous)
  composition varies made up of 2 or more pure
  substances

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How do you know what type of matter it is?

• Pure substances
• elements cannot be broken down into anything
  smaller than the representative atoms
• compounds can be chemically separated
  (decomposed), using chemical reactions

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How do you know what type of matter it is?

• Mixtures can be separated physically
• homogeneous same throughout no visibly
  different parts uniform a solution
• heterogeneous contains regions with different
  properties visibly different areas doesnt mix
  (not uniform)

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Types of Mixtures

• Variable combination of 2 or more pure substances.

Heterogeneous visibly separate parts
Homogeneous Same throughout
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Mixture Separation Techniques

• filtration - separation of solid from a liquid
  using filter paper
• only one for heterogeneous mixtures
• parts already have to be in different states for
  filtration to work
• distillation - depends on different boiling
  points of the substances in a solution

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Mixture Separation Techniques

• chromatography - separates parts of a solution
  using their different levels of attraction for a
  stationary substance
• crystallization - boils off liquid to leave
  crystallized (solidified) substance that had been
  dissolved in the liquid

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Matter Flowchart
yes
no
Can it be physically separated?
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Matter Flowchart
yes
no
Can it be physically separated?