Chemical Equations Guided Lesson

© The Science Duo

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A representation of a chemical reaction using
symbols of the elements

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Quick and easy way to show a chemical
reaction using symbols instead of words

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There are 2 sides to a chemical equation –
Reactants and Products

Chemical Equation for Photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2

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The elements or compounds on the left side of a
chemical equation

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Present before a reaction takes place

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“Ingredients” of a chemical reaction

Chemical Equation for Photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2

Reactants

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The elements or compounds on the right side of
a chemical equation

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Present after a reaction takes place

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New substances formed by a chemical reaction

Chemical Equation for Photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2

Products

Reactants Products

Arrow

2Fe2O3 + 3C

4Fe + 3CO2

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Matter cannot be created or destroyed

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The mass on the reactant side must equal the
mass on the product side

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If you begin a reaction with 100 g of substances,
you must end with the same amount

CaO + CO2 → CaCO3

40 g + 60 g = 100 g

Chemical equations must be balanced in order to follow

the Law of Conservation of Mass!

• Find the number of atoms of each element on the

reactant side

• Find the number of atoms of each element on the

product side

• If the number of atoms of each element are the same on

the reactant and product side then the equation is
balanced

• If the number of atoms of each element are NOT the

same then the equation is unbalanced

Identify one similarity
and one difference
of the reactants and

products in a

chemical equation.

Circle and label the reactants and
products in the chemical equation

shown below.

4FeS + 7O2 → 2Fe2O3 + 4SO2

According to the Law of

Conservation of Mass, how many
grams of water (H2O) should be

present on the product side?

4NH3 + 5O2 → 4NO + 6H2O

15 g + 65 g = 35 g + ____ g

Balanced or Unbalanced?

C2H6O + 3O2 → 2CO2 + 3H2O

Balanced or Unbalanced?

Ti2Cl4 + 2H2O → 2TiO2 + 4HCl

Multiple Choice

Is this balanced?
Al + O₂ → 2Al₂O₃

• Yes

• No

Multiple Choice

The substances listed on the right side of a chemical equation are the

• Yields

• Reactants

• Products

• Precipitates

Multiple Choice

The substances listed on the left side of a chemical equation are the

• Products

• Coefficients

• Precipitates

• Reactants

Multiple Choice

What coefficient should be used to make the following equation balanced?
N₂+O₂--> _NO 

• 1

• 2

• 3

• 4

Multiple Choice

What is the left part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical equation

Multiple Choice

What is the right part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical Equation

Multiple Choice

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO

Multiple Choice

What is the number before a chemical formula called?

Example: 2H₂ + O₂ ---> 2H₂O

• Coefficient

• Atom

• Subscript

• Equation

Multiple Select

__CH₄ + __O₂ --> __CO₂ + __H₂O

What are the reactants in this equation?

• CH₄

• O₂

• CO₂

• H₂O

Multiple Choice

In a chemical equation...

• a new substance is formed

• new atoms are formed

• old atoms disappear

• a equal sign is always used

Multiple Choice

Products are

• old substances

• new substances

• atoms that disappear

• atoms that do not exist

Multiple Choice

Reactants are

• new substances

• old substances

• likely to disappear

• likely to appear

Multiple Choice

Determined whether the following equation is balanced or unbalanced. Ag + O_{2 --->} 2Ag₂O

• Balanced

• Unbalanced

Multiple Choice

Determine whether the following equations is balanced or unbalanced. H₄ + O₂ ---> 2H₂O

• Balanced

• Unbalanced

Multiple Choice

Determine whether the following equation is balanced or unbalanced. H₂ + Br₂ ---> 2HBr

• Balanced

• Unbalanced

Multiple Choice

During an investigation, a student combined two substances as shown below. The student observed a decrease in temperature when the substances were combined. A milky substance formed and sank to the bottom of the flask. What is the most likely reason for these results?

• The decrease in temperature produced ice crystals.

• A solid appeared after the liquid evaporated.

• The combined substances chemically reacted.

• A portion of the substances dissolved.

Multiple Choice

Students in a science lab conducted an investigation. Students recorded the following observations. Which of the substances produced a chemical change?

• Substances 1 and 2

• Substances 1 and 3

• Substances 1 and 4

• Substances 2 and 3

Multiple Choice

How many Hydrogen (H) atoms are in 4NH₃?

• 4

• 1

• 3

• 12