10thgrad

e
Chemical
Reaction
MELC: Describe the motion of an object by
tracing and measuring its change in position
(distance travelled) over a period of time.
Matter undergoes two types of
changes. These are physical change
and chemical change. Physical
change involves only a change in
the appearance but not in
composition of the material.
Chemical change involves not only
A chemical reaction is usually
accompanied by one or combination
of the following: the production of
heat and light, the formation of a
precipitate, the evolution of gas, a
change in color of the material or
there is a change in temperature.
We can see that these events that
are happening when a chemical
Chemical reaction is a process in which
one or more substances are converted to
one or more different substances. In
other words, chemical reaction is the
process where a material is
transformed into a new one, possessing
a new composition.
Chemical changes are always represented by a
chemical equation. A chemical equation is a
symbolic representation of a chemical reaction.
There are two parts of a chemical equation, the
reactants and the products. Reactants are the
substances before reaction and written on the left
side of the chemical equation. Products are the
substances resulting from the reaction and
presented at the right side of the chemical
equation. The reactants and products are separated
by an arrow.
Take note that in writing chemical equations, certain
symbols are used. Below is the list of symbols used
in writing chemical equations.
 TYPES of CHEMICAL REACTION
1. Combination or Synthesis - a
reaction when two or more elements
combine to form a single product.
General equation: A + B → AB
Example: Sodium + Chlorine gas → Sodium
chloride
2. Decomposition - a single reactant
breaks down into simpler ones. It is the
opposite of combination reaction.
General equation: AB → A + B
Example: Sodium chloride → Sodium + Chlorine gas
3. Single Displacement
(Replacement) – A substance; it can be
an element or a compound; capable of
replacing one of the atoms of a given
compound.
General equation: AB + C → AC + B
Example: Potassium bromide + chlorine gas →
Potassium chloride + bromine gas
KBr + Cl2 → KCl + Br2
4. Double Displacement
(Replacement) – a reaction in which
ions get exchanged between two
reactants, resulting to the formation of a
new compound.
General equation: AB + CD → AD + C
Example: Silver nitrate + Magnesium chloride →
Silver chloride + Magnesium nitrate
AgNO3(aq) + MgCl2(s)) → AgCl(s) + MgNO3(aq)
5. Combustion (Burning) Reaction – a
reaction wherein oxygen gas combines
with a hydrocarbon; a compound
containing carbon and hydrogen atoms;
forming carbon dioxide and water as the
products.
General equation: CnHn + O2 → CO2 +
H2O
General equation: CnHn + O2 → CO2 + H2O
6. Acid-Base Reaction or Neutralization
Reaction - special kind of double
displacement reaction that takes place
when an acid and a base react. In
general, the products of this reaction are
salt and water.
General equation: Acid + Base → Salt +
Water
General equation: Acid + Base → Salt + Water
 Activity. Recognizing the Type of Chemical
Reaction
Directions: Classify the following
unbalanced chemical equations
according to the different types of
reactions. Use the given code below to
classify each reaction.
Code:
CR = Combination DRR = Double Replacement
DR = Decomposition CoR = Combustion
SRR = Single Replacement ABR = Acid-Base
 Activity. Recognizing the Type of Chemical
Reaction
1. O2 + N2 → NO2
2. HBr + NaOH→ NaBr + H2O
3. MgI2 + Mn(SO3)2 → MgSO3 + MnI4
4. AgNO3 + Cu → CuNO3 + Ag
5. CaSO4 + Mg(OH)2 → Ca(OH)2 + MgSO4
6. FeBr3 + Na → NaBr + Fe
7. Li + F2→ LiF
8. KClO3 → KCl + O2
9. H2 O →H2 + O2
10. CaCO3 → CaO + CO2
Balancing Chemical
Reactions
 The law of conservation of mass
is a scientific law popularized and
systematized by the 18th-century French
chemist Antoine Lavoisier..
 According to this law, matter cannot be
created nor destroyed— it can only be
changed. This means that for substances
undergoing chemical reaction, its total mass
before a chemical reaction takes place and after
a chemical reaction had occurred are the same.
In balancing chemical reactions, the
number of atoms involved before and
after the chemical reaction is
conserved. Simply, the number of
atoms are conserved.
As an example, when the element
sodium, Na(s), combines with chlorine
gas (Cl )(g), it forms sodium chloride,
2

NaCl(s).
 The balanced chemical equation for this
reaction is:
2 Na(s) +Cl2(g) → 2NaCl(s)

The balanced equation shows that the total

number of atoms in the reactants is equal to
the total number of atoms in the products.
Steps in Balancing Equation
 1. Identify the products and reactants
Remember, reactants are written on
the left side of your equation while the
products are on the right.
For this equation, reactants are the
metal iron, Fe, and oxygen gas, O , and 2

the product is Iron (III) oxide, Fe O .

2 3
 2. Write the number of atoms.
Next, you need to determine how
many atoms of each element are present
on each side of the equation. You can do
this by looking at the subscripts or the
coefficients.
4Fe + 3O → 2Fe O 2 2 3
Reactant - product
Fe – 4 -4
O–6 -6
 3. Add coefficients.
A coefficient is a whole number
multiplier and they are used to balance
chemical equations. They show how many
atoms or molecules of a substance are
involved in a reaction. To balance a
chemical equation, write appropriate
coefficients to make sure that the number
of atoms on both sides of the arrow are the
same. Use the simplest whole number ratio.
 3. Add coefficients.
In the equation below, a
coefficient 2 is placed before Fe2O3 that
makes 4 atoms of Fe atom and 6 atoms
of O. In the reactant side, a coefficient
4 is placed before Fe atom and
coefficient 3 is placed before O atoms
that makes 4 atoms of Fe and 6 atoms
of O.
3. Add coefficients.
 4.
Apply the Law of Conservation of
Mass to get the same number of atoms
of every element on each side of the
equation. The equation is now
balanced. They have the same number
of atoms on both sides.
Direction:
Identify the reactants and
products of the reaction. Check the
Equation if the number of atoms on
both sides are the same. Use a
separate sheet of paper for your
answers.
 1. When aqueous sodium bromide
reacts with chlorine gas, it produces
sodium chloride and bromine gas.

Cl 2 (g) + NaBr (aq) NaCl (aq) + Br 2 (g)

a. What are the reactants in the
equation above?
b. What are the products?
c. Check the equation if it conforms
with the Law of Conservation of
Mass.
d. Is the reaction balanced? Explain.
e. What is conservation of mass? How
does it relate to this exercise?
ACTIVITY:Balance the following chemical
equations.
2H2 (g) + O2 (g) 2 H2O(l)
R P
H: 2-4 2-4
O: 2-2 1-2
Thank
You!