Combustion reactions

Draw

Draw the Lewis Dot Structure of Methane

Open Ended

Why is methane considered a hydrocarbon?

Multiple Choice

Essential Question. Which will dissolve faster in hot tea granulated sugar or a sugar cube?

• sugar cube

• granulated sugae

Standard

SC.912.P.8.8

• Characterize types of reactions, for example: redox, acid-

base, synthesis, and single and double replacement
reactions and combustion.

Objectives

Understand that
in a combustion
reaction, the
products are
always the same.

01

Understand that
fire provides the
reactant oxygen
but is not part of
the reactants

02

Understand that
the symbol ,
represents heat.

03

Reaction Energy

• All chemical reactions result in a change in the

chemical energy of the reactants as they form the
products

Reaction Energy

•Chemical changes that give
off energy are called
exothermic reactions. A
combustion reaction is always
exothermic

Chemical changes that
absorb energy are
called endothermic
reactions.

Multiple Choice

The initial energy required to start a combustion reaction is called

• Potential Energy

• Kinetic Energy

• Chemical Potential Energy

• Activation Energy

Multiple Choice

A compound that contains only carbon and hydrogen and that produces carbon dioxide and water when burned is called a(n)

• binary compound

• carbonate

• ionic compound

• hydrocarbon

Multiple Choice

Balance the following combustion reaction. CH₄ + O₂ --> H₂O + CO₂.

• 1,2,2,1

• 2,2,2,2

• 1,1,1,1

• 2,1,1,2

Burning Methane

CH4 + 2O2
2H2O + CO2

These bonds
must be
broken

:These
bonds
must
form

Multiple Choice

The word equation for combustion is:
fuel + oxygen -->
 water + ________ __________

• Carbon dioxide

• Limewater

Combustion Clue:

Oxygen gas is a
reactant, and

carbon dioxide and
water are products.

Combustion

Exothermic Reactions

25oC

45oC

Gets hot

Hydrochloric
acid

magnesium

Magnesium + Hydrochloric acid

Endothermic Reactions

Ammonium
nitrate

Water

Cools

Heat
energy
taken
in as the
mixture
returns
back to
room
temp.

Collision

Theory

• For a chemical reaction to occur, the

particles involved must collide with each
other.

• The collisions must be with sufficient energy

to overcome the activation energy ‘barrier’.

• The rate of reaction (how quickly the

reaction occurs) depends on the number of
energy sufficient collisions per time.

Reaction

Energy

• The bonds between the atoms in

the reactants must first be
broken.

• For this to occur energy

must always be absorbed

• New bonds form as the products

are created

• Energy is always released as

this happens

Activation Energy

• The energy required to break the bonds of reactants

is called the activation energy.

• A diagram showing this is called an energy profile.

Catalyst

• Many reactions occur more rapidly in the presence of

particular elements or compounds.

• These substances, known as catalysts, are not consumed

during the reactions, they just help it along

• They often work by lowering the activation energy.
• Enzymes are biological catalysts.

Catalyst

Catalytic converters are used to convert the
polluting exhaust gases of burned lead-free gasoline
into harmless gases. Platinum (Pt) is the catalysts
used. Only a small amount is needed.

Combustion

2O2 + CH4 → CO2 + 2H2O

H

O

→

C

+

O

C

+

H

H

H

O

O
H

O

H

O O

O

H
H

• The charcoal used in a grill is basically carbon. The

carbon reacts with oxygen to yield carbon dioxide.
The chemical equation for this reaction is C + O2 →
CO2

A combustion reaction is when

oxygen combines with a hydro-
carbon and releases energy in the
form of heat and light. An example
of this kind of reaction involves
methane gas and oxygen.

Combustion

See a combustion reaction
with methane bubbles