Chemistry

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Chemistry
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Chemistry The central science

• Involves studying the properties and behavior of
  matter
• Provides understanding of the material world and
  how it works
• Answers questions about
• Composition and properties?
• Interaction with environment?
• How, why and when do they undergo change?

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Matter

• Matter is the physical material of the universe
• a) has mass, and
• b) takes up space (volume)
• Mass a measure of the amount of stuff (or
  material) the object contains (Units of Measure
  grams )
• Volume a measure of the space occupied by the
  object (Units of measure mL or cm3)

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Describing Matter

• Two types of properties used to describe matter
• Extensive Properties
• depends on the amount of matter in the sample
• Mass, volume, calories are examples
• Intensive Properties
• depends on the type of matter, not the amount
  present
• Hardness, Density, Boiling Point

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Physical Properties are

• Physical Properties-
• a property that can be observed and measured
  without changing the materials composition.
• Examples- color, odor, density, hardness, m.p.,
  b.p.

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Physical Change

• Physical change
• will change the visible appearance, without
  changing the composition of the material.
• Boil, melt, cut, bend, split, crack
• Can be reversible, or irreversible

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Chemical Properties are

• Chemical Properties
• The way a substance may change or react to form
  other substances
• a property that can only be observed by changing
  the composition of the material.
• Examples- ability to burn, decompose, ferment,
  react with, etc.

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Chemical Change

• Chemical change (a.k.a. Chemical Reaction)
• transformation of one substance into a
  chemically different substance
• Characteristics of a chemical change
• Change of color
• Change in temperature or energy
• the production (exothermic) or loss (endothermic)
  of heat.
• Change of form (for example, burning paper).
• Light, heat, or sound is given off.
• Formation of gases
• Formation of precipitate (insoluble particles).
• The decomposition of organic matter (for example,
  rotting food).

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States of matter

• Solid- matter that can not flow (definite shape)
  and has definite volume.
• Liquid- definite volume but takes the shape of
  its container (flows).
• Gas- a substance without definite volume or shape
  and can flow.
• Vapor- a substance that is currently a gas, but
  normally is a liquid or solid at room
  temperature. (Which is correct water gas, or
  water vapor?)

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States of Matter
Result of a TemperatureIncrease?
Definite Volume?
Definite Shape?
Will it Compress?
Small Expans.
Solid
YES
YES
NO
Small Expans.
Liquid
NO
NO
YES
Large Expans.
Gas
NO
NO
YES
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4th state Plasma - formed at high temperatures
ionized phase of matter as found in the sun
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Three Main Phases
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Liquid
Gas
Solid
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Copper Phases - Solid
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Copper Phases - Liquid
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Copper Phases Vapor (gas)
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Pure Substance

• A pure substance is matter that has distinct
  prosperities and a composition that doesnt vary
• All substances are either
• Elements
• or
• Compounds

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Elements

• Element
• Is a type of atom
• Identified by its atomic number
• Atomic Number the number of protons in its
  nucleus.
• A pure chemical substance composed of atoms with
  the same number of protons.
• Simplest kind of matter
• Cannot be broken down any simpler and still have
  properties of that element!
• One kind of atom.

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Molecule

• Atoms can combine to form molecules in which two
  or more atoms are joined together in specific
  shapes.
• You can have
• Molecules of an Element
• (example Br,I,N,Cl,H,O,F)
• and/or
• Molecules of a Compound
• (example a water molecule H2O)

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Compound

• Compounds
• A substance consisting of two or more different
  elements
• Chemically bonded together in a fixed proportion.
• Same composition and properties throughout
• Broken down only by chemical methods.
• When broken down, the pieces have
• different properties than the original
• compound.

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Mixtures

• Mixtures
• Are a physical blend of at least two substances
• Have variable composition.
• Each component substance retains its own chemical
  identity
• They can be either
• Heterogeneous
• Homogeneous

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Mixtures

• Heterogeneous
• The mixture is not uniform in composition
• Examples Chocolate chip cookie, gravel, soil.

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Mixtures

• Homogeneous
• Same composition throughout called solutions
• Examples Kool-aid, air, salt water

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Compound vs. Mixture
Compound
Mixture
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Other Types of Mixtures

• Solutions
• Colloids
• Suspensions

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Solutions

• Solutions are homogeneous mixtures
• Uniform throughout
• Can occur between any state of matter gas in
  gas liquid in gas gas in liquid solid in
  liquid solid in solid (alloys), etc.
• Examples soft drink, salt water, sugar water

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Colloidal Dispersion(Colloids)

• A colloid is a type of mixture where one
  substance is dispersed evenly throughout another.
  
• Colloidal particles are much larger than atoms or
  molecules.
• Particles larger than normal solutes (salt) but
  small enough to remain suspended in the
  dispersion medium (water)
• Colloids form dividing line between solutions and
  heterogeneous mixtures

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Colloid Examples
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Tyndall Effect

• The scattering of light by colloidal particles
• Tyndall scattering can be used to determine the
  size of colloidal particles.
• Example Prolonged and brilliantly coloured
  sunsets and twilights were frequently seen in
  London in the summer of 1815 due to Tyndall
  scattering of sunlight by ash particles in the
  upper atmosphere, produced by the earlier
  eruption of the volcano Tambora.

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Suspensions

• Suspension
• a heterogeneous fluid containing solid particles
  that are sufficiently large for sedimentation.
• Unlike colloids, suspensions will eventually
  settle.
• Examples sand in water, paint, dust in air

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Separating Mixtures

• Differences in physical properties can be used to
  separate mixtures.
• By hand
• With a magnet
• Filtration - separates a solid from the liquid in
  a heterogeneous mixture according to size

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Separation of a Mixture
Components of dyes such as ink may be separated
by paper chromatography.
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Separation of a Mixture
Distillation takes advantage of different
boiling points.
NaCl boils at 1415 oC
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Which is it?
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Classification of Matter