Balancing Chemical Equations Brittany Camp & David Mejia

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

Background At NASA’s 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.

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

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

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

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.

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.

Concept Look at this chemical equation: Al + O 2 Al 2 O 3 Oxygen gas is diatomic, it is always in pairs. A molecule of aluminum oxide consists of two aluminum atoms combined with three oxygen atoms.

Balancing the Equation We can balance the equation by looking at what is doesn’t 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 + O 2 Al 2 O 3 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 O 2 2Al 2 O 3 Now that we have the O balanced we find that Al is not, we must add 2 more Al to make it 4 4Al + 3O 2 2Al 2 O 3 Now if you count you will find that there are 4 Al atoms on each side and 6 O atoms. Balanced!

Example C 2 H 6 + O 2 CO 2 + H 2 O C 2 H 6 + O 2 CO 2 + 3H 2 O C 2 H 6 + O 2 2CO 2 + 3H 2 O C 2 H O 2 2CO 2 + 3H 2 O 2C 2 H 6 + 7O 2 4CO 2 + 6H 2 O Balanced!

Tips When balancing equations, there are several things you can do: You may never put numbers that alter the formula itself. H 2 O H 4 O 2 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.

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) + O 2 (g) MgO (s) 2 Mg (s) + O 2 (g) 2 MgO (s)

Description This activity is based on the game “Battle Ship,” where each player attempts to find where the other player’s ships are located on a grid. The objective of the game is to find where the opponent’s 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 player’s battle ships.

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 opponent’s 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.

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