Modeling & Balancing
Chemical Equations Lab
This activity a fun way to get your students
balancing, building, and modeling
chemical equations for simple reactions.
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Modeling Chemical Reactions Lab
LESSON PLAN
Teacher Notes and Lesson Plan
NGSS Standards:
• MS-PS1-5: Develop and use a model to describe how the total number of atoms
does not change in a chemical reaction and thus mass is conserved.
• HS-PS1-7: Use mathematical representations to support the claim that atoms, and
therefore mass, are conserved during a chemical reaction.
Objectives:
• Balance simple chemical equations.
• Construct and use a model to show how the total number of atoms does not
change in a chemical reaction.
Materials:
• Different colored candies (such as skittles) in the colors red, yellow, orange, green,
and purple. If you do not wish to use candies, you may choose to have the students
draw and color circles or cut / paste provided printable “candies” onto the spaces
on the lab sheet. You will need 12 green, 12 yellow, 4 orange, 4 purple, and 2 red
candies per student / group of students.
Lesson Plan:
Warm Up: Read in whole group (or individual) the provided article on chemical
equations. This gives an overview of parts of chemical reactions, balancing chemical
reactions, and conservation of mass. Have students answer provided pre-lab questions
that go with the above-mentioned reading. Review answers as a whole group and
consider a pair/share for this part of the lesson.
Activity: Have students balance and model the 5 different chemical equations.
Students will use color coded candies to model how atoms are rearranged, but matter
is conserved. Consider making this a partner activity. Breaking students into groups of
5 and assigning each student an equation, but making group members check each
other’s work, is a great way to accommodate a large class or students who may need
additional support.
Assessment: Check lab and pre-lab questions for accuracy and review answers with
students. To check answers as a whole group, I project the answer key on my board.
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Printable Candies in Color
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Na
Na
Na
Na
Na
Na
N
N
N
N
N
N
Cl
Cl
Cl
Cl
Cl
Cl
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Printable Candies in BW
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S t u d e n t s C o lo r I n Ato m s
Before Beginning
Na
Na
Na
Na
Na
Na
N
N
N
N
N
N
Cl
Cl
Cl
Cl
Cl
Cl
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M o d e l i n g C h e m i c a l E q u at i o n s L A B
Name:____________________________
A chemical reaction expresses a chemical change. For example, one chemical property of hydrogen is that it
will react with oxygen to make water.
hydrogen + oxygen à water
We can represent this chemical change in a chemical equation, which is a concise way of representing a
chemical reaction. Instead of the names of the elements involved in the reaction, chemical symbols are used. The
initial substances that react are called reactants. The final substances produced by the chemical change are called
products. The arrow indicates a chemical reaction is taking place.
H2 + O2
à
reactants
H2O
products
Although the chemical equation above represents the chemical reaction, it is an unbalanced chemical
equation. The law of conservation of mass explains that matter cannot be created or destroyed. In chemical
equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each
element in the products. Look at the unbalanced equation above. If we count the number of hydrogen atoms in the
reactants and products, we find that each side has two hydrogen atoms. However, if we count the number of oxygen
atoms in the reactants and products, we find that there are two oxygen atoms in the reactants, but only one oxygen
atom in the products. Unequal amount of oxygen atoms on each sides makes this equation unbalanced.
To balance this equation, you can change the number of atoms that react or are produced. You cannot change
the the subscripts of the chemical formula of any substance. To change the number of molecules produced, and
balance the equation, you can add a coefficient in front of the chemical formula of a substance. A coefficient in the
number placed in front of symbols or formulas in a chemical equation to indicate their relative amount. If a substance
does not have a coefficient, it is assumed to be 1.
A coefficient of 2 is added in front of H2O. Now both sides of the equation (reactants and products) have the same
number of atoms of each element. It is now a balanced equation with equal amounts of each type of atom on each
side of the equation.
Reactants
H=4
O=2
2 H2 + O2
Pre-Lab Questions
Describe the following terms in your own words.
à
coefficients
Products
H=4
O=2
2 H2O
subscript
6. Describe a difference and similarity between the
balanced and unbalanced chemical equation shown
below. Unbalanced: Fe + O à Fe O
2
1. Chemical Equation
2
3
Balanced: 4Fe + 3O2 à 2Fe2O3
2. Reactant
3. Product
7. Balance the following chemical equations.
4. Law of Conservation of Mass
A.
Zn +
B.
CS2 +
HCl à
H2
+
ZnCl2
5. Label the parts of the chemical equation below.
2H2 + O2
à
O2 à
CO2
+
SO2
2H2O
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M o d e l i n g C h e m i c a l E q u at i o n s L A B
Directions
For each problem set below, complete the following:
• Balance the chemical equation.
• Model the balanced equation with candies.
• Draw, label, and color your balanced candy molecule models.
• Write the balanced chemical equation.
Name:____________________________
Atom Candy Color Code
Red - Carbon (C)
Green - Hydrogen (H)
Yellow - Oxygen (O)
Orange - Sodium (Na) and Nitrogen (N)
Purple - Chlorine (Cl)
Balancing Rules
• Do not change subscripts, only coefficients.
• You must have the same number of candies (atoms of each element) on each side.
1
Word Equation
Hydrogen peroxide reacts to yield water and oxygen.
Reactants
Unbalanced Equation
H2O2
Products
H2O
+
O2
Balanced Equation
Candy Model
Labeled
+
# of Atoms of Each
Element
balanced equation
Balanced Chemical Equation
2
Word Equation
Nitrogen and hydrogen react to yield ammonia.
Reactants
Unbalanced Equation
N2
+
H2
Products
NH3
Balanced Equation
Candy Model
Labeled
+
# of Atoms of Each
Element
balanced equation
Balanced Chemical Equation
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M o d e l i n g C h e m i c a l E q u at i o n s L A B
3
Word Equation
Methane and oxygen react to yield carbon dioxide and water.
Reactants
Unbalanced Equation
CH4
+
Products
O2
CO2
+
H2O
Balanced Equation
Candy Model
Labeled
+
+
# of Atoms of Each
Element (balanced)
Balanced Chemical Equation
4
Word Equation
Oxygen reacts to yield ozone.
Reactants
Products
O2
O3
Unbalanced Equation
Balanced Equation
Candy Model
Labeled
# of Atoms of Each
Element (balanced)
Balanced Chemical Equation
5
Word Equation
Sodium carbonate reacts with hydrochloric acid to yield salt, water, and carbon dioxide.
Reactants
Unbalanced Equation
Balanced Equation
Candy Model
Labeled
Na2CO3
+
+
Products
HCl
NaCl
+
+
H2O
+
CO2
+
# of Atoms of Each
Element (balanced)
Balanced Chemical Equation
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KEY
M o d e l i n g C h e m i c a l E q u at i o n s L A B
A chemical reaction expresses a chemical change. For example, one chemical property of hydrogen is that it
will react with oxygen to make water.
hydrogen + oxygen à water
We can represent this chemical change in a chemical equation, which is a concise way of representing a
chemical reaction. Instead of the names of the elements involved in the reaction, chemical symbols are used. The
initial substances that react are called reactants. The final substances produced by the chemical change are called
products. The arrow indicates a chemical reaction is taking place.
H2 + O2
à
reactants
H2O
products
Although the chemical equation above represents the chemical reaction, it is an unbalanced chemical
equation. The law of conservation of mass explains that matter cannot be created or destroyed. In chemical
equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each
element in the products. Look at the unbalanced equation above. If we count the number of hydrogen atoms in the
reactants and products, we find that each side has two hydrogen atoms. However, if we count the number of oxygen
atoms in the reactants and products, we find that there are two oxygen atoms in the reactants, but only one oxygen
atom in the products. Unequal amount of oxygen atoms on each sides makes this equation unbalanced.
To balance this equation, you can change the number of atoms that react or are produced. You cannot change
the the subscripts of the chemical formula of any substance. To change the number of molecules produced, and
balance the equation, you can add a coefficient in front of the chemical formula of a substance. A coefficient in the
number placed in front of symbols or formulas in a chemical equation to indicate their relative amount. If a substance
does not have a coefficient, it is assumed to be 1.
A coefficient of 2 is added in front of H2O. Now both sides of the equation (reactants and products) have the same
number of atoms of each element. It is now a balanced equation with equal amounts of each type of atom on each
side of the equation.
Reactants
H=4
O=2
2 H2 + O2
à
coefficients
Pre-Lab Questions
Products
H=4
O=2
2 H2O
subscript
6. Describe a difference and similarity between the
balanced and unbalanced chemical equation shown
below. Unbalanced: Fe + O à Fe O
Describe the following terms in your own words.
2
1. Chemical Equation
A way of representing a chemical reaction using
symbols of the substances involved.
2
3
Balanced: 4Fe + 3O2 à 2Fe2O3
2. Reactant
Initial substances that react in a chemical reaction
3. Product
Substances produced by a chemical reaction
The unbalanced and balanced chemical equation
each represent a chemical reaction, and each have
the same substances as reactants and products.
The balanced equation has the same amount of
each element on each side of the the equation. The
unbalanced equation has unequal amounts of each
element on each side.
7. Balance the following chemical equations.
4. Law of Conservation of Mass
Matter cannot be created or destroyed
A.
Zn +
HCl à
Zn +
H2
2HCl à
+
ZnCl2
H2
+
ZnCl2
5. Label the parts of the chemical equation below.
reactants
2H2 + O2
subscripts
coefficient
à
B.
CS2 +
O2 à
CS2 +
2H2O
product
CO2
3O2 à
+
SO2
CO2
+
2SO2
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KEY
M o d e l i n g C h e m i c a l E q u at i o n s L A B
Atom Candy Color Code
Directions
For each problem set below, complete the following:
• Balance the chemical equation.
• Model the balanced equation with candies.
• Draw, label, and color your balanced candy molecule models.
• Write the balanced chemical equation.
Red - Carbon (C)
Green - Hydrogen (H)
Yellow - Oxygen (O)
Orange - Sodium (Na) and Nitrogen (N)
Purple - Chlorine (Cl)
Balancing Rules
• Do not change subscripts, only coefficients.
• You must have the same number of candies (atoms of each element) on each side.
1
Word Equation
Hydrogen peroxide reacts to yield water and oxygen.
Reactants
Unbalanced Equation
Products
H2O2
H2O
+
O2
Balanced Equation
Candy Model
Labeled
+
oxygen
2 Hydrogen peroxide
water
# of Atoms of Each
Element
balanced equation
4 H atoms
4 O atoms
4 H atoms
4 O atoms
Balanced Chemical Equation
2 H2O2
2
Word Equation
à
2 H2O
+
O2
Nitrogen and hydrogen react to yield ammonia.
Reactants
Unbalanced Equation
N2
+
Products
H2
Balanced Equation
Candy Model
Labeled
NH3
hydrogen
+
nitrogen
ammonia
# of Atoms of Each
Element
balanced equation
2 N atoms
6 H atoms
2 N atoms
6 H atoms
Balanced Chemical Equation
N2
+
3H2
à
2NH3
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KEY
M o d e l i n g C h e m i c a l E q u at i o n s L A B
3
Word Equation
Methane and oxygen react to yield carbon dioxide and water.
Reactants
Unbalanced Equation
CH4
+
Products
O2
CO2
+
H2O
Balanced Equation
Candy Model
Labeled
+
+
Carbon
dioxide
oxygen
methane
# of Atoms of Each
Element (balanced)
water
4 H atoms
4 O atoms
1 C atom
4 H atoms
4 O atoms
1 C atom
Balanced Chemical Equation
à
CH4 + 2 O2
4
Word Equation
CO2
+ 2 H2O
Oxygen reacts to yield ozone.
Reactants
Products
O2
O3
Unbalanced Equation
Balanced Equation
Candy Model
Labeled
ozone
oxygen
# of Atoms of Each
Element (balanced)
6 O atoms
6 O atoms
Balanced Chemical Equation
3 O2
5
Word Equation
à
2 O2
Sodium carbonate reacts with hydrochloric acid to yield salt, water, and carbon dioxide.
Reactants
Unbalanced Equation
Na2CO3
Balanced Equation
Candy Model
Labeled
+
HCl
NaCl
+
H2O
+
CO2
Salt
+
Sodium
carbonate
# of Atoms of Each
Element (balanced)
Products
2 Na atoms
3 O atoms
+
+
water
Hydrochloric
acid
1 C atom
2 Cl atoms
2 Na atoms
3 O atoms
Carbon
dioxide
1 C atom
2 Cl atoms
Balanced Chemical Equation
Na2CO3
+
2 HCl
à 2 NaCl
+
H2 O
+
CO2
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