Balancing Chemical Equations

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Balancing Chemical Equations

• Brittany Camp
• David Mejia

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Objective

• To be able to identify what is occurring in a
  chemical reaction and to be able to balance the
  equation between the reactors.

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Background

• At NASAs Spaceward Bound scientist are trying to
  find if there is life on Mars.
• The Mojave Desert resembles the terrain on Mars.
• The scientist run many different experiments to
  find if there is life in the Mojave Desert.

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Hypothesis

• If there is life in the soil in the Mojave
  Desert, then there could be life in the soil on
  Mars.

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Experiment

• Scientist collected soil samples from the Mojave
  desert, from many different locations.

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Experiment Continued

• The soil was labeled and put into test tubes.
• The test tubes where then added a solution.

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Experiment Continued

• If there was life in the test tube then the
  solution would turn blue.
• The more life there was the bluer it got.
• Then it was measured by a spectrometer.

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What is a Chemical Equation?

• When a chemical reaction occurs between solutions
  it can be described by an equation.
• This shows the chemicals that react (called
  reactants) on the left-hand side
• The two sides are separated by an arrow that
  shows what is yielded from the reactants.
• The chemicals that are produce (called products)
  on the right-hand side.

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Concept

• Look at this chemical equation
• Al O2 Al2O3
• Oxygen gas is diatomic, it is always in pairs.
• A molecule of aluminum oxide consists of two
  aluminum atoms combined with three oxygen atoms.

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Balancing the Equation

• We can balance the equation by looking at what is
  doesnt make sense in the equation. We see first
  that there are 2 Al on the right, so we add 2 to
  the left
• 2 Al O2 Al2O3
• Now there are the same number of Al atoms, we see
  that there is one more atom of O on the left, we
  must find a common factor of 6 on each side by
  adding 3 on the left 2 on the right
• 2 Al 3 O2 2Al2O3
• Now that we have the O balanced we find that Al
  is not, we must add 2 more Al to make it 4
• 4Al 3O2 2Al2O3
  
• Now if you count you will find that there are 4
  Al atoms on each side and 6 O atoms. Balanced!

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Example

• C2H6 O2 CO2 H2O
• C2H6 O2 CO2 3H2O
• C2H6 O2 2CO2 3H2O
• C2H6 3.5O2 2CO2 3H2O
• 2C2H6 7O2 4CO2 6H2O
• Balanced!

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Tips

• When balancing equations, there are several
  things you can do
• You may never put numbers that alter the formula
  itself.
• H2O H4O2     
• Don't worry if the numbers turn out to be
  fractions - you can always double or triple all
  the numbers at a later stage.
• If you recognize the atoms that make up a
  standard group such as sulphate, nitrate,
  phosphate, etc. that go unmarked throughout the
  chemical reaction, treat them as an indivisible
  item to be balanced as a whole.
• Leave molecules representing elements until last.
  This means that any numbers you put in front of
  those molecules won't unbalance any other
  molecule.

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States of Matter

• To make a chemical equation complete, the state
  of matter of each substance should also be
  included.
• (s) solid
• (l) liquid
• (g) gas
• (aq) aqueous (dissolved in water)
• Example solid magnesium ribbon burns in oxygen
  gas to form solid magnesium oxide
• Mg (s) O2 (g) MgO (s)
• 2 Mg (s) O2 (g) 2 MgO (s)

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Description

• This activity is based on the game Battle Ship,
  where each player attempts to find where the
  other players ships are located on a grid. The
  objective of the game is to find where the
  opponents battleship is and sink it.
• Mimicking this idea, the board would be set up
  with mini-test tubes filled with water and a
  clear, odorless solution that will react and
  change colors when a specific solution is added
  to it. The tubes with the clear, odorless
  solutions will act as each players battle ships.
  

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Procedure

• Start by creating a 4 by 3 grid of well plates
  that are filled with water. Then make three test
  tubes that are filled with a clear, odorless
  solution. The test tubes with the clear, odorless
  solution will act as the battleships and can be
  placed anywhere on the grid as long as they are
  next to each other.
• The game will be like regular battle ship. Each
  player will take turns attacking the opponents
  grid by dropping a solution into the beakers. If
  it is a miss, then the solution in the test
  tube will either change a specific color or not
  change at all. When there is a hit, the solution
  will change to a specific color. The first person
  to sink all of the battle ships wins.
• The students will learn then about what solutions
  were being used during the game and they will
  balance the equation between the two solutions
  that caused the chemical reaction. This is so
  students can see what is happening in the test
  tube when the two solutions are mixed.

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• This is what you guys are going to be doing
• Pb(NO3)2 KI   PbI2
  K(NO3)
• Pb(NO3)2 2KI   PbI2
  2K(NO3)