Download A Balancing Act

A Balancing Act
Chemical reactions are happening all around us. In a chemical reaction, atoms and
molecules interact, causing chemical changes. A chemical equation explains how
these reactions work. Reactants are the atoms or molecules that are present
before the reaction occurs and are written on the left side of a chemical equation.
Products are the atoms or molecules that form as a result of the chemical reaction
and are written on the right side of the equation.
The Law of Conservation of Mass states that “matter is neither created or
destroyed, but it can change form”. A chemical reaction follows the Law of
Conservation of Mass. The number of atoms present in the reactants is the same
as the number of atoms present in products, but in the course of the chemical
reaction, they may get rearranged.
Materials:
10 g copper chloride crystals
10 cm x 10 cm piece of aluminum foil
400 mL beaker
Glass stirring rod
Thermometer or temperature probe
100 mL graduated cylinder
Safety goggles
100 mL water
Procedure:
1. Observe the copper chloride crystals. Record your observations.
2. Add 100 mL of water to the beaker. Record the starting temperature of
the water in the data table.
3. Measure the mass of the copper chloride crystals, then add to the water in
the beaker. Stir and record the temperature. What do you observe?
4. Record your observations about the aluminum foil. Crumble up the foil into a
loose ball.
5. Place the aluminum foil ball into the beaker. Push it under the surface of
the liquid with the stirring rod.
6. Record the temperature every 15 seconds until the temperature stabilizes.
Record your observations as the reaction takes place.
7. Clean up the lab area as directed by your teacher.
Data Table A: Copper Chloride solution + aluminum foil
Time
Temperature
Observations
0 sec (starting)
0:15
0:30
0:45
1 minute
1:15
1:30
1:45
2 minutes
2:15
2:30
2:45
3 minutes
3:15
3:30
3:45
4 minutes
4:15
4:30
4:45
5 minutes
Data Analysis:
1. Name two physical changes that occurred in this activity.
2. What are some physical properties of:
Copper Chloride
Aluminum
3. Describe the appearance of the aluminum foil at the end of 5 minutes. Do you
think a new substance formed? Why?
4. How do you know that a chemical change occurred? List some of the changes
that occurred that would indicate a chemical change.
5. What happened to the temperature of the solution as the reaction progressed?
The chemical formula for the reaction that occurred in this activity is:
Al
+
CuCl2 
AlCl3 + Cu + (heat)
6. Inventory the number of atoms present on the reactant side of the equation.
Aluminum
Copper
Chlorine
7. Inventory the number of atoms present on the product side of the equation.
Aluminum
Copper
Chlorine
8. Is this equation balanced? How do you know?
9. Balance the equation by placing the correct coefficients before the reactants
and products.
___Al
+
___CuCl2 
___AlCl3 + ___Cu + (heat)
Remember the rules for balancing an equation:
1. You can only add coefficients.
2. You can never add subscripts.
3. A coefficient must be at the beginning of the compound formula and applies to
all elements in the compound.
4. For an equation to be balanced, there must be an equal number of each type of
atom on both sides of the equation.