Chemistry TAKS Review

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					Chemistry TAKS Review

       Fast Track
      Density
Density = mass
         volume
  D=M
    V
Math Tip for Density

    D= M
    1 V
  Cross Multiply
Buoyancy
                 Buoyancy
• The force that acts on objects immersed in or
  floating on a liquid




                                Photo from: http://www.seed.slb.com/en/scictr/watch/bathroom/duck.htm
                 Buoyancy
• Buoyancy is related to floating
• an object in a liquid is buoyed up (pushed up) by a
  force equal to the weight of the liquid the object
  displaces (pushes aside). This is known as
  Archimedes’ Principle.




                                 Photo from: http://www.seed.slb.com/en/scictr/watch/bathroom/duck.htm
Viscosity
                    Viscosity
• Viscosity is the resistance of a liquid to flow

• If a liquid flows slow, it is viscous, or has a
  high viscosity
Objective 4 - (I.7D)
 Periodic Table of the Elements
• An organized table of all the
  known elements
Atomic Number = Number of
         Protons
    Groups
• vertical columns
• contains elements with similar
  chemical properties
• EX: Li, Na, K
               Periods
• horizontal rows
• EX: K, Ca, Sc
• Staircase = Metalloids
                      (metal/non-metal combo)
• Right side + Hydrogen = Non-metals
• Left side = Metals
          Transition Metals
• Groups 3-12 are called transition metals
             Alkali Metals
• Group 1 (IA)
• Very reactive
Valence Electron: Outer
       Electron
                   Na
Number of valence electrons represented by
            the roman numerals
     Note this on your periodic table
Valence
electrons
• Every element wants 8 valence
  electrons to be stable
• Elements will lose or gain electrons
  (which ever is easier) to become stable
Predict if an element will lose or
  gain electrons? How many?
                Charges
• When electrons are gained or lost, a
  charge is formed
                                         1+
                                  Na
     Note this on your periodic table

1+             Charges                  0

       2+     3+         3-   2-   1-
          Noble Gases
• Group 18 (8A)
• Very stable & will not lose or gain
  electrons
• Unreactive
Writing Formulas
 To make an ionic compound, the
    charges must cancel out
1+         Charges                  0

     2+   3+         3-   2-   1-
    Goal: Cancel out the
          charges
Example:
     Magnesium + bromine
            +2        -
         Mg        Br
  I need two bromines to cancel out with 1 Mg

                 +               -
                 +               -

                MgBr2
Criss Cross Method
     +2        -1
Mg        Br
Criss Cross Method
     MgBr2
Criss Cross Method
      +3     -2
 Al        SO4
Criss Cross Method
   Al2(SO4 )
           3
Al2(SO4)3

                o        o
                                             SO4
                     S
            o                o
                                     o
    o               Al   Al
                                 s       o
o           s
                     o       o
                                     o
        o
          Physical Changes




More Examples
  – Cutting
  – Breaking apart
Law of Conservation of Mass

   Mass can not be created or
          destroyed
    Using the Law of Conservation of
                 mass
   2H2 + O2 à 2H2O
  100 grams     50 grams          ?
                              150 grams



   H2O(s) à H2O(l)
   32 grams                32 grams



   C + O2 à CO2
20 grams       ?
           40 grams    60 grams
Balancing Equations
A reaction must be balanced to
obey the law of conservation of
             mass
• Non-balanced Reaction
    H 2 + O 2 à H 2O


• Balanced Reaction
    2H2 + O2 à 2H2O
      How to balance a reaction
• Step one: list all the element symbols
  under the arrow of a reaction

     H 2 + O 2 à H 2O
                        H
                        O
     How to balance a reaction
• Step two: count how many of each atom
  you have on each side of the reaction

 H 2 + O 2 à H 2O

            2     H 2
            2     O 1
              Coefficients
• Numbers that are placed in front of a
  compound/molecules in a reaction
     How to balance a reaction
• Step three: add coefficients to the
  compounds to help make each element
  even on both sides

2 H 2 + O 2 à 2 H 2O
       4 2 H 2 4
         2 O 1 2
     The reaction

2 H2 + O2 à 2H2O
               Balance Me!

2          2         2     4
                           2
___ XeF2 + ___ H2O à __ Xe + __ O2 + __ HF

           2   1   Xe 1 2
           4   2   F 1 2 4
           4   2   H1 2 4
           2   1   O2
           Ions
           in solution

             Objective 4: IPC 9B
 TSW relate the concentration of ions in a
solution to physical and chemical properties
   such as pH, electrolytic behavior, and
                  reactivity
• Distilled water is pure water. It has no ions
  in it at all.

• An ion is any substance that has a charge.
  A charge is indicated by a + or - sign.

• Ions in solution (dissolved minerals) can
  conduct electricity.
Litmus Paper




Aci
Re D       B   ase
               lue
• More solute will result in a boiling point
  elevation (increase) and freezing point
  depression (decrease)
• Why do people put salt on icy roads?

				
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