GHSGT Review

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GHSGT Review

• Chemistry

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Whats on the test?

• The Atom
• Isotopes
• The Periodic Table
• Solutions
• States of Matter and Changes in State
• Radiation

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The Atoms Fundamental Parts

• An atom consists of 3 subatomic particles
• The proton
• The neutron
• The electron

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• Most of the MASS of an atom comes from the masses
  of
• Protons and Neutrons
• Live in the nucleus
• Electrons are outside the nucleus in the electron
  cloud.

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Whats so important about electrons?

• Electrons control chemistry of an atom.
• They exist in specific energy levels within the
  electron cloud

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Valence electrons

• Electrons in the highest energy level of an atom

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Atomic Number Mass Number

• Atomic Number- number of protons in the nucleus
  of an atom

• Mass Number- number of protons neutrons in an
  atom
• Very similar to the Atomic Mass
• Silver
• Protons 47
• Electrons 47
• Neutrons 108 47 61

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Isotopes

• Atoms of an element that
• Have the same numbers of protons
• Different numbers of neutrons

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• Metals most elements, all elements to the left
  of the zig zag line (except Hydrogen)
• Nonmetals elements to the right of the zig zag
  line
• Metalloids (semi-metals) elements on the zig
  zag line, have properties of both metals and
  nonmetals

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General (Physical) Properties

• Physical properties may be observed without
  changing the nature of the matter.
• Boiling point is a physical property
• The liquid is still the same substance
• Properties you can see, such as color, shape,
  hardness, and texture
• Properties that are easily measured, such as
  mass, volume, density, melting point, boiling
  point
• Note! Freezing and melting point are the same
  temperature!
• Density Mass Volume
• Is the ability to be attracted to a magnet a
  physical property?

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Physical versus Chemical Changes

• Physical changes are when no new substances are
  formed (i.e. phase changes such as melting,
  freezing, boiling, condensation, evaporation,
  sublimation)
• Chemical changes occur when new substances are
  formed (i.e. rusting, foaming, burning)
• Whether physical change or chemical change, MASS
  IS ALWAYS CONSERVED

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Metals

• Shiny
• Ductile
• Malleable
• Give up electrons easily
• Good conductors of heat and electricity

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Nonmetals

• Dull
• Brittle
• Nonconductors
• Usually gases or liquids at room temperature

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The Periodic Table

• Groups- vertical columns in the periodic table
• Elements in a group have similar chemical and
  physical properties
• Periods- horizontal rows in the periodic table

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Groups

• Group 1 (1A) alkali metals most reactive
  metals, never found by themselves in nature,
  always found combined with other elements

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• Group 2 (2A) Alkaline earth metals
• Also very reactive but not as much as alkali
  metals

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• Group 17 (7A)- Halogens
• Very reactive nonmetals

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• Group 18 (8A) Noble gases
• Do not react with much at all
• Very stable

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Periodic Trends

• The Periodic Table is set up in such a specific
  way so that one can see trends in physical and
  chemical properties of the elements
• Valence number
• Reactivity
• Ionization energy
• Atomic size
• Melting and boiling points

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Radiation

• Unstable elements tend to spontaneously break
  down.
• Usually because they have too many neutrons
  compared to their protons
• Radioactivity is where rays are spontaneously
  made by the nucleus of the atom. There are 3
  types of radioactive decay

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Radioactive Decay

• Alpha particles made up of 2 protons 2
  neutrons
• Can be stopped by a sheet of paper or skin, not
  very energetic
• Sometimes written as a helium nucleus (42He)

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Radioactive Decay

• Beta Decay made up of 1 electron
• More energetic, can be stopped by a sheet of foil

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Radioactive Decay

• Gamma Rays mass-less energy, very dangerous
• Can be partially stopped by 6 inches of lead or 6
  feet of concrete.

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Uses of Radioactivity

• Medicine
• Form of therapy of cancer
• X- rays
• Radioactive elements can be used as tracers that
  follow certain chemical reactions in living
  organisms

• Industry
• Food can be exposed to gamma rays to kill
  bacteria and parasites
• Radiocarbon dating
• Radioactive isotopes are used to date fossils

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Elements Compounds

• Elements
• Found on the periodic table
• Made of atoms
• Pure substances
• All atoms of an element are identical

• Compounds
• Made of 2 or more elements chemically joined
  (BONDING)
• Pure substances
• Made up of molecules
• All molecules of a compound are identical

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Forming Ions and Compounds

• Metals lose their valence electrons to become
  positively charged ions (CATIONS)

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• Nonmetals gain or steal electrons from metals
  to become negatively charged (ANIONS)

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Common Ions
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Forming Compounds

• Positive and negative ions combine so that their
  total charge adds up to zero when forming a
  compound.

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Pure Substances vs. Mixtures

• Pure Substances
• Elements
• Compounds
• Composition NEVER changes

• Mixtures
• Heterogeneous Mixtures
• Homogeneous Mixtures (also called SOLUTIONS)
• Variable compositions

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Heterogeneous Mixtures

• Each component in the mixture is distinguishable
  from each other
• Examples

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Homogeneous Mixtures (Solutions)

• Exists in one phase (looks all the same)
• Examples

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Solutions

• Solute the substance that gets dissolved
• Solvent the substance that does the dissolving

• Water is the UNIVERSAL SOLVENT
• Waters unique properties give it the ability to
  dissolve many different types of solutes
• Polar (Ex. NaCl)
• Nonpolar (Ex. C11H22O11)

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Solutions

• Saturated solutions the solvent has dissolved
  as much solute as possible
• There will be a small amount of solute in the
  bottom of the solution.

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Solutions

• Unsaturated solutions more solute can easily
  dissolved into the solution.
• Supersaturated solution more than the normal
  amount of solute is dissolved that seems
  possible. (video)
• http//www.9news.com/video/default.aspx?maven_play
  erIdsfspanglermaven_referralObject996471809

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States of Matter

• Solid definite shape and volume, not
  compressible
• Liquid definite volume but not shape, takes
  shape of container, slightly compressible
• Gas takes shape and volume of its container,
  very compressible
• Plasma high energy ionized gas, occurs in stars
  lightening

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Changing States of Matter

• Melting solid to a liquid
• Freezing liquid to a solid
• Boiling (Vaporizing) liquid to a gas
• Condensation gas to a liquid
• Sublimation solid to a gas
• Deposition gas to a solid

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Which is which?
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Changing states of matter
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Good luck! You can do it!!!