Basics of Chemistry

1
Basics of Chemistry

• Biology

2

• Atoms are the basic unit of matter.
• Atoms are made of small subatomic particles
  protons, neutrons, electrons

3
History of the Atom

• Democritus a fifth century B.C. Greek philosopher
  proposed that all matter was composed of
  indivisible particles called atoms (Greek for
  uncuttable).

4
Models of the Atom

• Billiard Ball Model  (1803)
• Plumb Pudding Model (1897)
• Solar System Model
• In 1913 Neils Bohr proposed that electrons
  traveled in circular orbits and that only certain
  orbits were allowed.  This model of the atom
  helped explain the emission spectrum of the
  hydrogen atom.  He received the Nobel Prize in
  physics in 1922 for his theory.

5
Bohr Model
6
1st energy level 2 electrons
2nd energy level 8 electrons
3rd energy level 18 electrons
4th energy level 32 electrons
7

• Electron Cloud Model (1920's)- an atom consists
  of a dense nucleus composed of protons and
  neutrons surrounded by electrons that exist in
  different clouds at the various energy levels. 

8
Atoms
9

• Electrons have a negative charge, Protons have a
  positive charge and neutrons have no charge.
• Protons and neutrons make up the nucleus
• Electrons surround the nucleus

10
Particle Type Charge Location in the atom Mass
Proton () positive Nucleus 1  a.m.u.
Neutron (0) neutral Nucleus 1  a.m.u.
Electron (-) negative Electron Cloud 0  a.m.u.
11
Matter

• Matter can be divided or classified into three
  classes called elements, mixtures, and compounds.
  
• Elements  Pure substances made up of only one
  type of atom.  All matter is made of atoms.  The
  types of atoms or matter are listed on the
  periodic table of elements. 

12

• Elements are represented by chemical symbols.
  Some examples are Cu for copper and H for
  hydrogen. 

13
(No Transcript)
14
Compounds

• Compounds  Pure substances made up of two ore
  more elements combined chemically.  Compounds are
  represented by chemical formulas such as H2O for
  water and CO2 for carbon dioxide. 
• Compounds that contain carbon are called organic
  compounds and compounds that do not contain
  carbon are called inorganic compounds. 

15
Mixtures

• Mixtures Mixtures are not pure.  They are made
  up of two or more substances combined physically,
  but are not chemically.  Mixtures can easily be
  separated while pure substances can not.
• Mixtures may or may not have the same composition
  throughout.  Mixtures may be more than one color
  or a solid color.   Any substance that is
  multicolored is a mixture.

16
Types of Mixtures

• Homogeneous mixture  has the same composition
  through out     Ex fresh milk, mayonnaise
• Heterogeneous mixture  does not have the same
  composition through out     Ex Unstirred
  chocolate milk, unshaken italian dressing

17
  Law of Conservation of Mass and Energy

• Law of Conservation of Mass and Energy  A set
  amount of matter  and energy exists in the
  universe.  New matter and energy can not be
  created.  Matter and energy can not be destroyed.
  
• Matter and energy are interchangeable.  Matter
  can be turned into energy and energy can be
  turned into matter.

18

• All matter may be classified into four physical
  states or phases
• Solid  has a definite shape and volume, the
  molecules are very close together and vibrate
  very slowly in place.
• Liquid  has a definite volume, but no definite
  shape.  Liquids take the shape of their
  container.  Molecules are further apart and move
  slowly.
• Gas  has no definite volume and no definite
  shape.  Molecules will move as far apart from
  each other as possible and move very fast.
• Plasma an electrically charged gas.  Molecules
  move faster than a gas.  The sun is made of
  plasma.  Plasma can not usually be contained on
  earth with our current technology.

19
Kinetic Theory of Matter

• When you add heat energy, molecules move faster
  and further apart.  When you remove heat energy,
  molecules move slower and closer together.  This
  is what causes matter to change from one state to
  another.  For example,  when you add heat energy
  to ice, the molecules move faster and further
  apart turning it into a liquid.

20
Transitions of matter

• Evaporation  When a substance changes from a
  liquid to a gas.
• Condensation  When a substance changes from a
  gas to a liquid.
• Sublimation  When a substance changes from a
  solid to a gas, skipping the liquid phase (dry
  ice).

21

• Boiling Point  The temperature at which a
  substance turns from a liquid to a gas.
• Freezing Point  The temperature at which a
  substance turns from a liquid to a solid.
• Melting Point  The temperature at which a
  substance turns from a solid to a liquid.

22
Bonds

• An attraction between two or more atoms.
• There are three types of bond covalent
  (sharing), ionic (transfer) and van der Waals
  forces (attraction between molecules)

23
Covalent Bond

• Atoms will share electrons in order to have their
  outer most energy level filled.  When atoms are
  connected together because they are sharing
  electrons, this is called a covalent bond.

24
Molecule

• Two or more atoms held together by a covalent
  bond.

25
Ionic Bonds

• Atoms lose or gain electrons.  One atom will lose
  its electron(s) and another atom will gain its
  electron(s).  When an atom loses an electron, it
  becomes a positively charged ion.  When an atom
  gains an electron, it becomes a negatively charge
  ion.  Oppositely charged ions attract to each
  other forming an ionic bond.