Chemical Reactions

CHEMICAL REACTIONS
CHEMICAL REACTIONS
Subject Physics and Chemistry
Course/Level 4º ESO
Primary Learning Objective Analyze chemical reactions in terms of quantities and product formation.
Subject Content 1. Introduction to chemical reactions.
1.1. Signs of chemical reactions.
1.2. Chemical equations: law of conservation of matter.
1.3. The mole concept.
2. Types of chemical reactions.
3. Gas Laws.
3.1. Boyle’s law.
3.2. Charles law.
3.3. Gay-Lussac’s law.
3.4. Avogadro’s law.
4. Stoichiometry.
4.1. Stoichiometry island diagram.
4.2. Real life problem solving.
Language Content /
Communication
Vocabulary Arrow, exothermic, chemical equation, ionic equation, chemical reaction, precipitate, coefficient, product, decomposition
reactant, single replacement, double replacement ,electrolysis, synthesis, endothermic …
Structures Routines: How can we express the quantity of substances?
Why chemists do choose to work in moles?
What are the uses of symbols and formulas in determining moles of substances ?
What is the difference between mass of an atom and atomic mass?
Contents: Conditionals, present, future, comparatives.
Classroom management: Take out your notebook/recorder/pen, write down the following sentence, right! / you're right,
well done! / very well! / good job , etc.
Discourse type Exposition, description, argument.
Language skills Writing, reading, speaking and listening
Activities The presentation includes different activities with an explanation in order to the students answer a question or solve a problem, make
observations and collect data, and draw a conclusion as to the answer to the question or problem.
LESSON PLAN
Pp Jaramillo Romero
Dpto. Física y Química
IES Rodríguez Moñino

CHEMICAL REACTIONS
METHODOLOGY
Organization and class distribution / timing The number of sessions considered to develop the contents on this unit are at least 8 sessions of 50 minutes each one (+ 2 week final Project)
It’s very important to point out that the methodology will be active and participatory in order to facilitate both individual and group learning. For that, teacher
observation is very important during student's work.
Key Competences Language proficiency Know, acquire and apply the vocabulary of the subject.
Exercising a comprehensive reading of texts related to the topic.
Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or
performing technical tasks.
Digital competence and treatment of
information
I use PDI to explain content and implementation of web quest by students.
Make the online activities.
Social and civic competences Fostering respect between and other values like cooperation, coeducation when they work in groups.
Autonomy and personal initiative To be autonomous for individual activities.
Analyse the specific results based on explanations in the text.
Mathematical competence Solve a variety of stoichiometry problems (ex. mass-mass, mol-mol, mass-mol, etc.)
Evaluation Acquired content knowledge (*) Analyse the stoichiometric relationships inherent in a chemical reaction.
Analyse the Law of Conservation of Matter and how it applies to various types of chemical equations (synthesis,
decomposition...)
Interpret coefficients of a balanced equation as mole ratios.
Use mole ratios from the balanced equation to calculate the quantity of one substance in a reaction given the
quantity of another substance in the reaction.
Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or
performing technical tasks.
How to balance a chemical reaction equation using the conservation of matter law.
Write both word and formula equations, what the subscripts after a letter mean and what the numbers in front
of compounds mean.
Learn what a mole ratio is and how to determine and write the mole ratio relating two substances in a chemical
equation.
To make mole-to-mole calculations and solve problems involving moles of substances.
Instruments The unit will be evaluated daily with:
Individual participation in classroom activities and homework.
Works in groups.
Notebook.
Behavior.
Tests.
Glossary.
Conceptual maps.
Lab experiments.
Final Project.
(*) Depends on the student’s level.
Pp Jaramillo Romero

CHEMICAL REACTIONS
1. Introduction to chemical reactions.
1.1. Signs of chemical reactions.
1.2. Chemical equations: law of conservation of matter.
1.3. The mole concept.
2. Types of chemical reactions.
3. Gas Laws.
3.1. Boyle’s law.
3.2. Charles law.
3.3. Gay-Lussac’s law.
3.4. Avogadro’s law.
4. Stoichiometry.
4.1. Stoichiometry island diagram.
4.2. Real life problem solving.
OUTLINE
Pp Jaramillo Romero

CHEMICAL REACTIONS
 How can we express the quantity of
substances?
 Why chemists do choose to work in moles?
 What are the uses of symbols and formulas
in determining moles of substances ?
 What is the difference between mass of an
atom and atomic mass ?
CHEMICAL REACTIONS
Pp Jaramillo Romero

CHEMICAL REACTIONS
1. INTRODUCTION TO CHEMICAL REACTIONS
Pp Jaramillo Romero
Physical changes
Are concerned with energy and states
of matter. A physical change does not
produce a new substance, although the
starting and ending materials may look
very different from each other.
Chemical and
physical
changes are
related to
chemical and
physical
properties
Changes in state or phase
(melting, freezing, vaporization,
condensation, sublimation)
Breaking a bottle
Crushing a can
Chemical changes
Take place on the molecular
level. A chemical change
produces a new substance.
Another way to think of it is
that a chemical change
accompanies a chemical
reaction.
Rusting of an iron pan
Burning
Cooking an egg
Activity 1.1: Physical and chemical changes

CHEMICAL REACTIONS
1.1. SIGNS OF CHEMICAL REACTIONS
Pp Jaramillo Romero
A chemical change makes a substance that wasn't there before. There may be clues
that a chemical reaction took place, such as light, heat, colour change, gas production,
odour, or sound.
There are a number of observations that
indicate a chemical reaction has occurred. One
is the formation of a precipitate. A precipitate
is a solid formed in a chemical reaction that is
different from either of the reactants.
A colour change may also indicate that a
chemical reaction has occurred. A reaction has
occurred if two solutions are mixed and there
is a colour change that is not simply the result
of a dilution of one of the reactant solutions.

CHEMICAL REACTIONS
1.1. SIGNS OF CHEMICAL REACTIONS
Pp Jaramillo Romero
The formation of a gas is the third sign that a
reaction may have occurred. The formation of
bubbles when two liquids are mixed usually
indicates that a gas has formed.
An increase or decrease in temperature both
indicate that a chemical reaction is occurring.
Here the temperature increased when two
liquid samples were mixed.
Activity 1.1.1: Video: Definition of chemical reaction

CHEMICAL REACTIONS
1.2. CHEMICAL EQUATIONS: LAW OF CONSERVATION OF MATTER
Pp Jaramillo Romero
A chemical equation is the symbolic representation of a chemical reaction.
Depict the kind of reactants and products and their relative
amounts in a reaction.
4 Al(s) + 3 O2(g) 2 Al2O3(s)
The letters (s), (g), and (l) are the physical states of compounds.
The numbers in the front are called stoichiometric coefficients.
This equation means:
4 Al atoms + 3 O2 molecules yield 2 molecules of Al2O3
4 Al moles + 3 O2 moles yield 2 moles of Al2O3
or

CHEMICAL REACTIONS
Pp Jaramillo Romero
Because the same atoms are present in a reaction at the beginning
(reactants) and at the end (products), the amount of matter in a
system does not change.
Law of Conservation of Matter
Lavoisier
is that, in a closed system, matter cannot be created or
destroyed. It can change forms, but is conserved. The law of
conservation of mass is a relation stating that in a chemical
reaction, the mass of the products equals the mass of
the reactants. Antoine Lavoisier stated, "atoms of an object
cannot be created or destroyed, but can be moved around and
be changed into different particles".
Activity 1.2.1: Law of conservation of mass

CHEMICAL REACTIONS
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Because of the principle of the conservation of matter,
An equation must be balanced.
It must have the same number of atoms of the same kind on
both sides.
Unbalanced and balanced equations

CHEMICAL REACTIONS
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Balanced equation
One in which the number of atoms of each element as a reactant
is equal to the number of atoms of that element as a product
Balancing Chemical Equations
• Write a word equation for the reaction.
• Write the correct formulas for all reactants and products.
• Determine the coefficients that make the equation balance.
Activity 1.2.2: Video: Introduction to Balancing Chemical Equations
Activity 1.2.3: Video: Balancing Chemical Equations/Types of Reactions

CHEMICAL REACTIONS
Pp Jaramillo Romero
Determine whether the following equation is balanced.
2 Na + H2O  2 NaOH + H2
2 Na + 2 H2O  2 NaOH + H2
Activities
Is this balanced?
NO(g) + O(g)  NO2(g)

CHEMICAL REACTIONS
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Symbols used in chemical equations

CHEMICAL REACTIONS
1.3. THE MOLE CONCEPT
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A burrowing mammal with
fossorial forefeet
A small congenital
pigmented spot
on the skin
An undercover agent,
a counterspy,
a double agent
A breakwater
A mole is…
A unit of measure for an amount of a chemical substance.
Activity 1.3.2: Video: Singing a song
Activity 1.3.1: Video: Introduction to moles
Activity 1.3.3: Video: Happy mole day to you

CHEMICAL REACTIONS
Pp Jaramillo Romero
This number is called AVOGADRO’s number
NA = 602213673600000000000000
or 6.022 x 1023 particles/mol
In Chemistry a mole is the amount of substance that contains as
many particles (atoms or molecules) as there are in 12.0 g of the
isotope of carbon-12.
1 mole ~ 602.2 sextillions
Amadeo Avogadro (1766-1856)
never knew his own number;
it was named in his honor by a
French scientist in 1909.
Its value was first estimated
by Josef Loschmidt, an Austrian
chemistry teacher, in 1895.

CHEMICAL REACTIONS
Pp Jaramillo Romero
• 1 dozen cookies = 12 cookies
• 1 mole of cookies = 6.022 X 1023 cookies
• 1 dozen cars = 12 cars
• 1 mole of cars = 6.022 X 1023 cars
• 1 dozen Al atoms = 12 Al atoms
• 1 mole of Al atoms = 6.022 X 1023 atoms
Note that the NUMBER is
always the same, but the
MASS is very different!
Mole is abbreviated mol.

CHEMICAL REACTIONS
Pp Jaramillo Romero
Activity 1.3.5: Video: Converting between grams and
moles
Activity 1.3.6: Video: Converting between moles, atoms, and
molecules
Activity 1.3.4: Video: How big is a mole?
Activity 1.3.7: Moles and mass relations exercises
Activity 1.3.8: Mole calculations
Activity 1.3.9: Practice problems
Activities

CHEMICAL REACTIONS
2. TYPES OF CHEMICAL REACTIONS
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Five Types of Chemical Reactions:
1. Combustion
3. Decomposition
4. Single Displacement
5. Double Displacement
2. Synthesis

CHEMICAL REACTIONS
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1. Combustion
When a substance combines with oxygen releasing a large
amount of energy in the form of light and heat, it is a
combustion reaction.
•In general:
CxHy + O2  CO2 + H2O
•Products in combustion are ALWAYS carbon dioxide and water.
(although incomplete burning does cause some by-products like
carbon monoxide)
•Combustion is used to heat homes and run automobiles (octane,
as in gasoline, is C8H18)

CHEMICAL REACTIONS
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2. Synthesis
When two substances (generally elements) combine and form a
compound. (Sometimes these are called combination or addition
reactions).
Basically: A + B  AB
Example: 2H2 + O2  2H2O
Example: C+ O2  CO2

CHEMICAL REACTIONS
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3. Decomposition
When a compound breaks up into the elements or in a few to
simpler compounds
In general: AB  A + B
Example: 2 H2O  2H2 + O2
Example: 2 HgO  2Hg + O2

CHEMICAL REACTIONS
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4. Single Displacement
When one element replaces another in a compound.
A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-).
A + BC  AC + B (if A is a metal) OR
A + BC  BA + C (if A is a nonmetal)
(remember the cation always goes first!)

CHEMICAL REACTIONS
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5. Double Displacement
• When a metal replaces a metal in a compound and a
nonmetal replaces a nonmetal in a compound.
In general: AB + CD  AD + CB
Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)
Another example:
K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s)

CHEMICAL REACTIONS
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Single and double replacement reactions
Double-replacement reaction
CaCO3 + 2 HCl  CaCl2 + H2CO3
General form:
AB + CD  AD + CB
Single-replacement reaction
Mg + CuSO4  MgSO4 + Cu
General form:
A + BC  AC + B

CHEMICAL REACTIONS
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Activity 2.2: Video: Five types of chemical reactions
Activity 2.3: Video: Types of chemical reactions
Activity 2.1: Video: 5 Types of Chemical Reactions Lab
Activities
Activity 2.4: Let’s go to the lab!

CHEMICAL REACTIONS
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3. GAS LAWS
One of the most amazing things about gases is that, despite wide
differences in chemical properties, all the gases more or less obey the
gas laws. Gas laws deal with how gases behave with respect to pressure,
volume, temperature, and amount.
Gas properties can be modeled using math.
Model depends on:
V = volume of the gas (liters, L)
T = temperature (Kelvin, K)
P = pressure (atmospheres, atm)
n = amount (moles, mol)

CHEMICAL REACTIONS
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3. GAS LAWS
Pressure - Temperature - Volume Relationship
Gay-Lussac’s P Ta
Charles V Ta
Boyle’s P
1
Va
___

CHEMICAL REACTIONS
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3.1. BOYLE’S LAW Pressure - Volume Relationship
Boyle's law or the pressure-volume law states that the volume of a given amount of gas
held at constant temperature varies inversely with the applied pressure when the
temperature and mass are constant.
(V is proportional to the inverse of P)
Another way to describing it is saying that their products are constant.
PV = Cte
When pressure goes up, volume goes down. When volume goes up, pressure goes down.
From the equation above, this can be derived:
P1V1 = P2V2 = P3V3 etc.
P
1
Va
___
Activity 3.1.1: Boyle's Law

CHEMICAL REACTIONS
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3.2. CHARLES LAW
Activity 3.2.1: Charles Law
Temperature - Volume Relationship
This law states that the volume of a given amount of gas held at constant pressure
is directly proportional to the Kelvin temperature.
(V is proportional to T)
Same as before, a constant can be put in:
V / T = Cte
As the volume goes up, the temperature also goes up, and vice-versa.
Also same as before, initial and final volumes and temperatures under constant
pressure can be calculated.
V1 /T1 = V2 /T2 = V3 /T3 etc.
V Ta

CHEMICAL REACTIONS
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3.3. GAY-LUSSAC’S LAW
Activity 3.3.1: Gay-Lussac's Law
Pressure - Temperature Relationship
This law states that the pressure of a given amount of gas held at constant volume
is directly proportional to the Kelvin temperature.
(P is proportional to T)
Same as before, a constant can be put in:
P / T = Cte
As the pressure goes up, the temperature also goes up, and vice-versa.
Also same as before, initial and final volumes and temperatures under constant
pressure can be calculated.
P1 /T1 = P2 /T2 = P3 /T3 etc.
V Ta

CHEMICAL REACTIONS
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3.4. AVOGRADO’S LAW
Activity 3.4.1: Avogadro's Law
Volume - Amount Relationship
Gives the relationship between volume and amount when pressure and temperature are
held constant. Amount is measured in moles. Also, since volume is one of the variables,
that means the container holding the gas is flexible in some way and can expand or contract.
If the amount of gas in a container is increased, the volume increases. If the amount of gas
in a container is decreased, the volume decreases.
(V is proportional to n)
As before, a constant can be put in:
V / n = Cte
This means that the volume-amount fraction will always be the same value if the pressure
and temperature remain constant.
V1 /n1 = V2 /n2 = V3 /n3 etc.
V na

CHEMICAL REACTIONS
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3. GAS LAWS
The previous laws all assume that the gas being measured is an ideal gas,
a gas that obeys them all exactly. But over a wide range of temperature,
pressure, and volume, real gases deviate slightly from ideal. The ideal gas
law is:
R is a constant called the universal gas constant and is equal to approximately
0.0821 L-atm / mole-K.
Activity 3.1: Gas laws exercises

CHEMICAL REACTIONS
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3. GAS LAWS
1 mol of a gas=22.4 L
at STP
Molar Volume at STP
Standard Temperature & Pressure
0°C and 1 atm

CHEMICAL REACTIONS
4. STOICHIOMETRY
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The mass of one element
combines with a fixed mass of
another element in a ratio of
whole numbers.
All samples of a given
chemical compound have the
same elemental composition
Mass of the products equals the mass of the
reactants
One of the most important parts of chemistry is stoichiometry. Stoichiometry is the
study of the quantities of reactants and products in a chemical reaction. The word
comes from the Greek words: stoicheion ("element") and metron ("measure").
Sometimes you'll see stoichiometry covered by another name: Mass Relations. It's a
more easily pronounced way of saying the same thing.

CHEMICAL REACTIONS
4. STOICHIOMETRY
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Almost all stoichiometric problems can be solved in just four
simple steps:
1.Balance the equation.
2.Convert units of a given substance to moles.
3.Using the mole ratio, calculate the moles of substance yielded
by the reaction.
4.Convert moles of wanted substance to desired units.
These "simple" steps probably look complicated at first glance,
but relax, they will all become clear.
STOICHIOMETRY STEPS

CHEMICAL REACTIONS
4.1. STOICHIOMETRY ISLAND DIAGRAM
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Mass
Particles
Volume Mole Mole
Mass
Volume
Particles
Known Unknown
Substance A Substance B
Use coefficients
from balanced
chemical equation1 mole = 22.4 L @ STP 1 mole = 22.4 L @ STP
(gases) (gases)

CHEMICAL REACTIONS
4.2. REAL LIFE PROBLEM SOLVING
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Airbag Design
2 NaN3(s)  2 Na(s) + 3 N2(g)
6 Na(s) + Fe2O3(s)  3 Na2O(s) + 2 Fe(s)
Assume that 65.1 L of N2 gas are needed to inflate an air bag to the
proper size. How many grams of NaN3 must be included in the gas
generant to generate this amount of N2?
(Hint: The density of N2 gas at this temperature is about 0.916 g/L).
How much Fe2O3 must be added to the gas generant for that
amount of NaN3?

CHEMICAL REACTIONS
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Water from a Camel
Camels store the fat tristearin (C57H110O6) in the hump. As well as
being a source of energy, the fat is a source of water, because when
it is used the reaction takes place.
2 C57H110O6(s) + 163 O2(g)  114 CO2(g) + 110 H2O(l)
What mass of water can be made from 1.0 kg of fat?

CHEMICAL REACTIONS
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Rocket Fuel
The compound diborane (B2H6) was at one time
considered for use as a rocket fuel. How many
grams of liquid oxygen would a rocket have to
carry to burn 10 kg of diborane completely?
(The products are B2O3 and H2O).

CHEMICAL REACTIONS
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Water in space
In the space shuttle, the CO2 that the crew exhales is removed
from the air by a reaction within canisters of lithium hydroxide.
On average, each astronaut exhales about 20.0 mol of CO2 daily.
What volume of water will be produced when this amount of CO2
reacts with an excess of LiOH?
(Hint: The density of water is about 1.00 g/mL.)

CHEMICAL REACTIONS
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Activity 4.2.1: Tutorial and problem set
Activity 4.2.2: Reaction worksheets
Activities

CHEMICAL REACTIONS
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- https://www.youtube.com/watch?v=Wwmsy4huZQ0
- https://www.youtube.com/watch?v=X328AWaJXvl
- https://www.youtube.com/watch?v=SEB5r7DW5So
- https://www.youtube.com/watch?v=yA3TZJ2em6g
- https://www.youtube.com/watch?v=wI56mHUDJgQ
- https://www.youtube.com/watch?v=4B8PFqbMNIw
- https://www.youtube.com/watch?v=TEl4jeETVmg
- https://www.youtube.com/watch?v=nsEkKIiOz7Q
- https://www.youtube.com/watch?v=9U6uYRk-2ds
- https://www.youtube.com/watch?v=HMAOrGpkTsQ
- https://www.youtube.com/watch?v=CMnkSb2YsXI
- https://www.youtube.com/watch?v=ReMe348Im2w
- https://www.youtube.com/watch?v=1R7NiIum2TI
VIDEOS
BIBLIOGRAPHY

CHEMICAL REACTIONS
Pp Jaramillo Romero
- https://www.youtube.com/watch?v=eYeRA--Xq0E
- https://www.youtube.com/watch?v=bWhs5L_gBTI
- https://www.youtube.com/watch?v=Cr7xGEI0KDc
- https://www.youtube.com/watch?v=fexEvn0ZOpo
- https://www.youtube.com/watch?v=nsEkKIiOz7Q
VIDEOS
BIBLIOGRAPHY

CHEMICAL REACTIONS
Pp Jaramillo Romero
- https://es.khanacademy.org/science/chemistry/chemical-
reactions-stoichiome
- http://woodridge.k12.oh.us/ourpages/users/dweaver/Chemistr
y/PracticeWorksheets/ReactionWorksheets.html
- http://dl.clackamas.edu/ch104-03/practice.htm
- http://www.famousscientists.org/amedeo-avogadro/
- http://www.chemteam.info/Stoichiometry/Stoichiometry.html
- http://www.halesowen.ac.uk/chemistry/mole_calculations.htm
- http://www2.southeastern.edu/Academics/Faculty/wparkinson
/help/atoms_and_molecules/test.html
- http://www.harpercollege.edu/tm-
ps/chm/100/dgodambe/thedisk/chemrxn/signs4.htm
- http://www.iq.poquoson.org/hssci/chemistry/gaslaws/hsgasla
ws06tlm.htm
BIBLIOGRAPHY
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Chemical Reactions

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