Atomic Rearrangement Lab
Name __________________________
7th Grade PSI Science
Grade
/ 30
Experiment Question:
How do the atoms of reactant substances form the product substances?
Hypothesis Starters:
1. What happens to the atoms of a reactant substance during a chemical reaction?
Explain your thinking.
2. Is it possible in a chemical reaction to have atoms in the product substances that
were not present in the reactant substances? Explain your thinking.
Purpose:
During this experiment, you will explore how the atoms that make up reactant
substances reform into the product substances. There are two very important ideas to
keep in mind during this experiment. The first idea is “The Law of Conservation of
Mass.” It means the total mass of the reactant substances must equal the total mass of
the product substances. Mass cannot be lost or gained during a chemical reaction. The
second idea is “The Law of Conservation of Matter.” It tells us that the atoms of the
reactant substances are the only ones that may be used to make the product
substances. This means if the product substance needs to have twelve hydrogen atoms
because of its chemical formula, the reactants need to have twelve hydrogen atoms as
well. If they don’t, we need more reactants as you will see while you work your way
through this experiment. (HINT: Now that you have read this, double check your
answer to Hypothesis Starter #2.)
During this experiment, you will also work with models to represent what is going
occurring. Since atoms are so small, you can’t work with them easily and see what is
happening. Instead of working with actual atoms, you will be using model atoms (either
model kits or maybe even candy) to keep track of what atoms are available for use.
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Remember, the point of the models is to help you visualize what is going on even
though it is too small for you to see normally. Also, if you are using candy for your
models, do not eat the candy unless your teacher tells you that it is safe at the end of
the experiment. If the candy ever touches the laboratory bench, it is not safe. There is
no “five second rule” in the laboratory.
Materials:
For each group:


One set of models
One set of colored pencils, crayons, markers, etc.
For Teacher:

Demonstration setups per teacher instructions.
Procedure:
1. Complete the color code table below to help you keep track of what color
represents what type of atom throughout the experiment.
Element
Color
Hydrogen
Carbon
Oxygen
Nitrogen
Sodium
Chlorine
2. For each reaction, count out the indicated number of molecule “sets” of atoms.
3. Arrange them in molecule “sets” as indicated on the reaction template.
4. Compare the reactant sets to the product sets to see if Mass and Matter were
conserved.
5. If your teacher has a demonstration of the reaction, you will also need to make
before and after observations about what happened.
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Reaction Template:
Reactant Sets
Product Sets
Reaction #1: Acid / Base Reaction
Reactants:
One hydrochloric acid set of one hydrogen and one chlorine
One sodium hydroxide set of one sodium, one oxygen and one hydrogen
Products:
One water set of two hydrogens and one oxygen
One sodium chloride set of one sodium and one chlorine
Draw a picture of what you see in your reaction template below.
Reactant Sets
HCl
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+
Product Sets
NaOH
H2O
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+
NaCl
Chemical Reactions and Energy
Complete the following chart by counting the atoms on each side to see if atoms are
conserved.
Reactant
Atoms
Element
Product
Atoms
Hydrogen
Chlorine
Sodium
Oxygen
Are the atoms conserved in this reaction? YES or NO
(HINT: if the numbers of each element match on the reactant and product sides,
atoms are conserved. If even one element does not have matching numbers, it
is not conserved.)
Observations of teacher demonstration:
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Reaction #2: Fizzing Soda
Reactants:
One carbonic acid set of two hydrogens, one carbon, and three oxygens
Products:
One water set of two hydrogens and one oxygen
One carbon dioxide set of one carbon and two oxygens
Draw a picture of what you see in your reaction template below.
Reactant Sets
Product Sets
H2CO3
H2O
+
CO2
Complete the following chart by counting the atoms on each side to see if atoms
are conserved.
Reactant
Atoms
Element
Product
Atoms
Hydrogen
Carbon
Oxygen
Are the atoms conserved in this reaction? YES or NO
Observations of teacher demonstration:
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Reaction #3: Metal + Acid Version #1
Reactants:
One sodium
One nitric acid set of one hydrogen, one nitrogen, and three oxygens
Products:
One hydrogen gas set of two hydrogens
One sodium nitrate set of one sodium, one nitrogen, and three oxygens
Draw a picture of what you see in your reaction template below.
Reactant Sets
Na
+
Product Sets
HNO3
H2
+
NaNO3
Complete the following chart by counting the atoms on each side to see if atoms
are conserved.
Reactant
Atoms
Element
Product
Atoms
Sodium
Hydrogen
Nitrogen
Oxygen
Are the atoms conserved in this reaction? YES or NO
(HINT: if the numbers of each element match on the reactant and product sides,
atoms
are conserved. If even one element does not have matching
numbers, it is not conserved.)
Observations of teacher demonstration:
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Reaction #4: Metal + Acid Version #2
Reactants:
Two individual sodiums
Two nitric acid sets of one hydrogen, one nitrogen, and three oxygens
each
Products:
One hydrogen gas set of two hydrogens
Two sodium nitrate sets of one sodium, one nitrogen, and three oxygens
each
Draw a picture of what you see in your reaction template below.
Reactant Sets
2Na
+
Product Sets
2HNO3
H2
+
2NaNO3
Complete the following chart by counting the atoms on each side to see if atoms
are conserved.
Reactant
Atoms
Element
Product
Atoms
Sodium
Hydrogen
Nitrogen
Oxygen
Are the atoms conserved in this reaction? YES or NO
(HINT: if the numbers of each element match on the reactant and product sides, atoms
are conserved. If even one element does not have matching numbers, it is not
conserved.)
Observations of teacher demonstration:
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Reaction #5: Burning Alcohol
Reactants:
One isopropyl alcohol set of three carbons, eight hydrogens, and one
oxygen
One oxygen gas set of two oxygens
Products:
Four water sets of two hydrogen and one oxygen each
Three carbon dioxide sets of one carbon and two oxygens each
Draw a picture of what you see in your reaction template below.
Reactant Sets
C3H7OH
+
Product Sets
O2
4H2O +
3CO2
Complete the following chart by counting the atoms on each side to see if atoms
are conserved.
Reactant
Atoms
Element
Product
Atoms
Carbon
Hydrogen
Oxygen
Are the atoms conserved in this reaction? YES or NO
Observations of teacher demonstration:
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Laboratory Questions:
On a sheet of paper or in your laboratory notebook, answer the following questions
about the experiment.
1. Which reactions obeyed the Law of Conservation of Mass and the Law of
Conservation of Matter? Explain your thinking.
2. Which reactions did not obey the Law of Conservation of Mass and the Law of
Conservation of Matter? Explain your thinking.
3. How many more oxygen gas molecule sets would be needed to balance
Reaction #5? Draw a reaction picture to show your answer.
Conclusion:
On a sheet of paper or in your laboratory notebook, write one or two paragraphs that
summarize the experiment results and cover the following key points.
1.
2.
3.
4.
Explain in your own words what the Law of Conservation of Mass means.
Explain in your own words what the Law of Conservation of Matter means.
Explain how you can use a model to tell if a reaction equation is balanced.
Explain how you can balance an equation if you see that Mass and Matter are
not conserved.
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