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SUBJECT
NATURAL SCIENCES
TITLE OF LEARNING OBJECT
CURRICULAR AXIS
STANDARD COMPETENCIES
LEARNING OBJECTIVES
SKILLS/ KNOWLEDGE
LEARNING FLOW
GRADE
SCIENCE 9th GRADE
LEARNING UNIT
HOW DO THE COMPONENTS OF THE
WORLD CHANGE?
What happens at atomic and molecular levels when we dissolve salt in
water
Science, Technology and Society
Verify the differences between chemical changes and mixtures.
ü To represent the dissociation of strong electrolytes in water.
ü To identify the relationships among the masses of the periodic
table elements.
ü To describe the importance of ions in the process of transmission
of nerve impulses.
ü To recognize that using heavy metals in industrial processes and
when manufacturing products generates a high environmental
impact and has negative effects on the health of living beings.
ü Establish proportional relationships between the masses of the
elements using atomic weights from the periodic table.
ü Prepare aqueous solutions of ionic and nonionic solutes.
ü Establish differences between the behavior of an ion pair on crystal
and in aqueous solutions.
ü Represent the role of ions in the process of transmission of nerve
impulses.
ü Inquire about industrial processes that generate accumulation of
heavy metals in the environment and analyze their impact on the
health of living beings.
1. Introduction
2. Objectives
ASSESSMENT
GUIDELINE
3. Activities
4. Activity 1
ü Skill
ü The Mass of the Elements
ü Very Important
ü The Ions Soup
ü Learning Activity 1
5. Activity 2
ü Skill
ü Ions and the Nerve Impulse
ü Did you know that…?
ü Learning Activity 2
6. Activity 3
ü Skill
ü Heavy Metals
ü Learning Activity 3
7. Abstract
8. Homework
9. Evaluation
10. Glossary
11. Vocabulary Box
12. English review topic
13. Bibliography
This learning object looks to help the student recognize the relationships
between the masses of the elements in the periodic table, identify the
dissociation process of ionic and non-ionic substances in aqueous
solutions, describe the importance of ions in the nerve impulses
transmission, and recognize that the use of heavy metals in industrial
processes and in the making of products causes a high environmental
impact and negative effects on the health of living beings.
Stage
Introduction
Learning flow
Introduction
Teaching/Learning Activities
Recommended
Resources
Start by mentioning the contents that will be seen in each Animation
activity, so that the student gets a context and a logical about what
framework for the development of said activities.
happens when
we disolve salt
Do you like soup? Can you imagine a soup without salt? It in water.
is possible that you have had to add some salt to a soup
sometimes before; however, it is very likely that you have
not thought about what happens with those little crystals
when they make contact with the soup.
Throughout this learning unit, we invite you to recognize
some properties of the chemical elements that give flavor
to a soup, sweeten a juice, and transmit information
between neurons.
Additionally, we will inquire about the negative effects
produced by using a group of chemical elements known as
heavy metals, which are part of different products, from
cell phone batteries, to the toothpaste that you use daily.
Content
Activity 1
This activity covers the following three skills:
Image
resource
Skill 1: Establish proportional relationships between the about the
masses of the elements using atomic weights from the mass of the
elements.
periodic table.
Skill 2: Prepare aqueous solutions of ionic and nonionic
Ludic Very
solutes.
important..
Skill 3: Establish differences between the behavior of an
ion pair on crystal and in aqueous solutions.
Video resource
about the
On this first part, present the concept of atomic mass and difference
the proportional relationships between the masses of the between mass
elements.
and weight.
The Mass of the Elements
Each chemical element is a type of atom that is different
from other atoms based on the number of protons that it
has (atomic number). When a scientist discovers a new
atom, he gives it a name and places it in the periodic table
according to its atomic number. Oxygen, hydrogen, and
carbon are names given to some atoms.
An important characteristic of each atom is its mass,
meaning the amount of matter that forms it. The atomic
mass is determined by the masses of protons and
neutrons together. As the electrons are so tiny, they are
not taken into account to determine the mass of an atom.
Figure 1. Representation of the atomic number and
atomic
mass
of
Sodium.
Retrieved
from:
http://es.123rf.com/imagenes-dearchivo/lanthanoids.html?mediapopup=24509724
Very important…
Mass expresses the amount of matter in a body, and
although mass and weight seem to be the same thing,
they are different terms. While weight changes with
respect to gravity, mass stays invariable.
For farther research on the topic, go to the following
video:
[Tegon Storm]. (2013, September 18). Diferencia entre
Masa
y
Peso [Video
file].
Retrieved
from:
https://www.youtube.com/watch?v=XZB924RFXJ8https://
www.youtube.com/watch?v=XZB924RFXJ8
https://www.youtube.com/watch?v=XZB924RFXJ8
The unit used to measure the atomic mass is the atomic
mass unit (u). The mass of each proton and each neutron
equals 1u. For example, an oxygen atom has 8 protons
and 8 neutrons, therefore its mass is constituted by 16
units of atomic mass (8 protons + 8 neutrons = 16u).
Therefore, the larger the atomic number of an element,
the larger its mass will be.
Next, present some of the interactions that occur in the
solutions of ionic and non-ionic solutes in an aqueous
medium.
To do so, there are
contextualize the student.
some
examples
that
allow
Image
resource
Additionally, you will find resources such as images and about the ions
web links to videos. Use them as support to enrich the soup.
contents.
Animation
The Ions Soup
resource
about the
Each time someone puts some salt into a Sancocho, or a solute and
spoonful of sugar into a mango juice, without thinking solvent.
about it, they are causing a chemical reaction between the
Video resource
salt and sugar molecules and the water molecules.
about salt
Substances such as salt and sugar have the ability to dissolve.
disintegrate in a liquid, in a process called solubility.
Thanks to this ability, people can flavor soups or sweeten
a juice.
In order to understand how solubility works, first we need
to study the electric characteristics of solutes and
solvents, as they allow the interaction of the molecules.
In a Sancocho the salt is the solute (dissolving substance)
and the water is the solvent (substance in which the solute
dissolves). The combination of solute and solvent is called
solution.
Both the salt and the water in a Sancocho are substances
made by atoms, this is why their electric characteristics
are determined by their atoms.
Atoms are formed by protons with a positive charge,
neutrons without any charge, and electrons with a
negative charge. When an atom has the same number of
protons and electrons, its electric charges cancel each
other, and the atom presents a neutral charge.
If an atom loses an electron when joining another atom,
then its charge becomes positive (+), but if the atom wins
an electron, its charge becomes negative (-). When the
atom gains any charge, it becomes an ion, therefore ions
are atoms with a negative or positive charge.
An atom with positive charge is called a cation, and an
atom with negative charge is called an anion.
When we mix sodium (Na) and chlorine (Cl), the sodium
atom gives an electron to the chlorine atom; therefore,
the sodium atom becomes an ion with positive charge
(Na+) and the chlorine atom becomes an ion with
negative charge (Cl-). The difference in the charges
between both ions will keep this molecule together (+ and
– attract each other).
Figure 2. Representation of the formation of a sodium
chloride molecule through the union of sodium and
chloride atoms. Designed by the author.
The type of tie that is formed between two ions is called
an ionic tie. An ionic tie between two atoms is similar to
the union of two magnets, in both cases the positive and
negative poles are attracted to each other.
Sodium and chlorine form sodium chloride (NaCl)
molecules, known as table salt. When many of these
molecules adhere to each other, they form small crystals
that can be seen with the naked eye when we take a little
bit of salt with our hands.
Sugar (sucrose) also forms crystals. It is formed by 12
carbon atoms, 22 from hydrogen and 11 from oxygen.
When these atoms bond, they do not give their electrons
to each other, they share them. This type of tie is known
as a covalent bond.
Figure 3. Representation of the sugar molecule. Retrieved
from: http://www.um.es/molecula/gluci04.htm
Sucrose molecules are not ionic, but they present partial
electric charges that are much weaker than the ones from
ionic substances. This is how t sucrose has atoms with
partially negative charges, such as hydrogen (H), and
partially positive such as in oxygen (O).
In ionic bonds electrons are lost and won, whereas in
covalent bonds electrons are shared.
Another substance, very different from salt and sugar, is
water. A water molecule is formed by two atoms of
hydrogen (H2) and one oxygen atom (O). The atoms of
this molecule present partial charges, just as the sugar
molecule.
In water molecules, two hydrogen atoms are partially
positive while the oxygen atom is partially negative; thus,
the water molecule is polar, as it has a side with positive
charge and the other side with negative charge.
Figure 4. Water molecule representation, in which its
partial positive and negative charges are shown. Retrieved
from: https://catquimica.cat/2011/04/04/les-aigues/
Water, in its in liquid state, is an excellent solvent given
its polar character, and due to the fact that its molecules
usually tie very easily to other molecules.
When we add salt (NaCl) to water (H2O), the chlorine ions
(Cl-) are attracted by the partially positive charges of
hydrogen, while the sodium ions (Na+) are attracted by
the partially negative charges of oxygen. That is how the
molecules that form the salt crystals disintegrate in Na+
and Cl- ions, surrounded by H2O.
Refer to the following video:
[shmibarra]. (2007, May 7). Disolución de sal de mesa.
Retrieved from: https://www.youtube.com/watch?v=HCRm5HX1hchttps://www.youtube.com/watch?v=HCRm5HX1hc
In a salt and water solution, most of the sodium and
chlorine ions remain separate, but some of them bond for
a short time, even when they are tied to water molecules.
This association of ions and water molecules is known as
ionic pair.
Figure 5. Representation of the formation of ionic pairs
due to the attraction of sodium and chlorine ions in an
aqueous
solution.
Retrieved
from:
http://catalog.flatworldknowledge.com/bookhub/4309?e=
averill_1.0-ch17_s02
When we add sugar to water, the sugar crystals do not
disintegrate in atoms. In this case, the sugar molecules
structure remains, only they separate from each other,
given that the water interrupts the bonds that keep them
together.
In the soup, the salt will dissolve until it separates from its
atoms, due to the strong attraction that the ions generate
for the water molecules. In the case of juice, the sugar
molecules will not disintegrate in atoms, as its main partial
charges do not produce as much attraction for the water
molecules to break all the bonds and ties.
Learning Activity 1
Work on the following activity that will help to strengthen
the knowledge on the relationships between the masses of
the elements in the periodic table.
“The amount of matter that forms
determined by the mass of its atoms.”
a
molecule
is
Bearing in mind the previous statement, and with help
from the periodic table, determine the mass (units of
atomic mass) of a water molecule in a mango juice glass,
and choose the correct answer.
A.
B.
C.
D.
16
18
17
20
u
u
u
u
Answer key: A water molecule is formed by two hydrogen
atoms and one oxygen atom. Each hydrogen atom has a
mass of 1u and the oxygen atom has a mass of 16u.
Therefore, when we add the masses of the atoms,
1+1+16, we get 18u.
2. This activity will help you to remember some of the
main characteristics of the relationships between chemical
elements and review the use of the passive voice in
present simple.
Chose a verb from the word bank to complete the
following
statements.
Remember
to
include
the
appropriate form of the verb to be.
to take
to know
to share
to attract
to determine
to form
to call
A. The atomic mass ____________ by the masses of
protons and neutrons together.
B. Electrons are so tiny that they ____________ into
account in the mass of an atom.
C. The combination of solute and solvent ___________ as
solution.
D. Atoms __________ by protons with a positive charge,
neutrons without any charge, and electrons with a
negative charge.
E. An atom with positive charge __________ cation, and
one with negative charge, anion.
F. In the atoms, the positive and negative poles
__________ to each other.
G. In the covalent bonds electrons__________.
Answer key:
A. is determined
B. are not taken
C. is known
D. are formed
E. is called
F. are attracted
G. are shared
Activity 2
This activity covers the following skill:
The teacher
presents the
topic
Skill 4: Represent the role of ions in the process of
transmission of nerve impulses.
Present the role of ions in the production of nerve
impulses. Use the resource “Did you know that…?” and the
image to support the content.
Image
resource
about ions and
Ions also have an important role in transmitting the the nerve
information that a person gets through the senses and, in impulse.
general, in the communication processes between the
Ludic Did you
neurons that make the nervous system.
know that…?
When a person is stimulated by light, temperature,
pressure, or a chemical substance, it generates an
electrical current called nerve impulse, which travels
through the neurons that form a network in the entire
body.
Ions and the Nerve Impulse
For example, when we take a family trip to a river, it is
normal to get mosquito bites, especially from jejenes.
When these tiny insects bite someone’s skin, specialized
cells, called sensory receptors, receive this sensation and
turn it into nerve impulses that travel through the neuron.
The nerve impulses occur thanks to changes in the
concentration of ions located both outside and inside the
neuron’s membrane.
Outside a neuron membrane there are sodium ions (Na+),
with positive charge, and inside the membrane, there are
potassium ions (K-), with negative charge.
Did you know that…?
The moderate intake of salt gives the required sodium
(Na) for an adequate function of the neurons. However,
the excessive consumption of salt can cause health
problems, such as arterial hypertension. This is why you
should never put too much salt on your food.
The membrane of a neuron has channels that allow the
flow of ions between inside and outside the cell. That is
how a stimuli such as a bite from jején is received. These
channels activate and, as a result, there is a change in the
concentration of positive and negative charges (change in
polarity) on the membrane.
Figure 6. Representation of the generation of a nerve
impulse by moving ions through the cell membrane of a
neuron. Designed by the author.
Changes in polarity at the membrane of a neuron turn into
electric current that goes through the cell in one single
direction, this way, it allows information to be transmitted
within the neuron network that forms the nervous system.
Learning Activity 2
Do this activity to help reinforce the knowledge about the
importance of ions in the transmission process of nerve
impulses.
To be able to do it, carefully read the statement and the
possible answers. Then choose the correct answer:
“When a jején bites a person, sensory receptors perceive
this sensation and turn it into nerve impulses.”
Based on the previous statement, which one of the
following sentences is true?
a.
The nerve impulse occurs thanks to the fact that the
jejenes produce an electrical current when they bite.
b.
The nerve impulse caused by the bite of a jején is a
current that goes through the neuron in all directions.
c.
The nerve impulse occurs thanks to the changes in
the concentration of sodium and potassium ions located
outside and inside the membrane of the neurons.
Answer:
Activity 3
a. False. The jejenes do not produce electric a current, the
current that is produced is due to the change in the
polarity of the neuron’s membrane.
b. False, as the same nerve impulse travels in a single
direction.
C. True.
This activity covers the following skill:
Image
resource
Skill 5: Inquire about industrial processes that generate about heavy
accumulation of heavy metals in the environment and metals.
analyze their impact on the health of living beings.
Animation
Dear teacher, next the relationship between heavy metals resource
and their negative effects on the health of living beings is about the
presented. You will find some contextualization examples consequences
and an image that you can use to enrich your class.
of heavy
metals use.
Heavy Metals
There are some chemical elements that are key to the
biological processes of living beings. However, there is
also a group of elements known as heavy metals that can
be harmful to living beings, including plants and animals.
The term “heavy metals” is used to talk about a group of
chemical elements that are toxic that includes arsenic,
chrome, cobalt, nickel, copper, zinc, silver, cadmium,
mercury, titanium, selenium, and lead.
Heavy metals can be found in nature as minerals and are
used as raw materials to make products such as: paint,
car batteries, electric batteries for cell phones and
computers, fertilizers for crops, soda cans, toothpaste,
makeup, etc.
If heavy metals are normally found in nature, why are
they toxic for living beings?
The concentrations of heavy metals in nature are normally
very low, so living beings can be in contact with them
without being harmed. In fact, it is normal to find heavy
metals in very low concentrations in the water of lakes,
rivers and seas.
When a man extracts heavy metals to use them as raw
materials, he needs to raise the concentration of such
materials. When the concentrations of heavy metals rise,
these become toxic for the living organisms.
How is it that heavy metals can pollute the environment?
Heavy metals are transformed different products that the
consumers use all around the world. According to the type
of product, we use it for a certain amount of time. A can of
food will be thrown away minutes after it was opened,
while a battery can be used for months.
The main pollution problems caused by heavy metals
occur after the products made with these materials are
thrown away without taking the necessary precautions for
their disposal.
An example of this is electric batteries. When an electric
battery cannot produce energy anymore it is discarded,
and although in Colombia there are collection campaigns
for an adequate disposal of these items, many batteries
end up in dumpsters, rivers, lakes, and oceans.
Electric batteries are made of heavy metals such as
manganese dioxide, zinc, silver oxide, and mercury oxide,
among other elements. When the battery oxidizes, the
components inside it are released into the environment.
Figure 7. Representation of a battery components,
including heavy metals such as zinc. Retrieved from:
http://www.ecured.cu/Pila_el%C3%A9ctrica
If a battery is disposed of on the ground, the rainwater will
spread its toxic content polluting the soil, eliminating
microorganisms and making the plants in the area ill. If
the battery is disposed of in water, the contamination level
will be higher, as the pollutants will go straight into the
fish and animals that are there.
Gold mining is one of the other main polluting agents by
heavy metals in Colombia, as a consequence of the
mercury used to separate the gold from the rocks in which
it is found, without any control whatsoever of the channels
and rivers that are close to the mines.
One of the places with the highest heavy metals pollution
rates in the country is a place called Segovia, located in
the northeast of Antioquia, in which gold mining is the
main economic activity of its inhabitants.
The impacts of heavy metals pollution in living beings’
health are very diverse. One of the effects on plants is the
reduction of photosynthesis and, as a consequence, the
delay of their growth. In animals, including human beings,
the most frequent effect is the destruction of neurons and
damage to the nervous system.
Learning Activity 3
The following learning activity should be done activity
based on the information presented on Activity 3.
Carefully read the following statements and fill in the gaps
with the missing words.
a.
The _______________ are chemical elements that
are toxic for living beings.
b.
In the gold mining done in Antioquia there is a high
level of pollution due to the bad use of ____________,
this element is classified as a heavy metal.
c.
Damage to the __________ system of the animals is
one of the most frequent effects of pollution by heavy
metals.
Abstract
Abstract
Answer key:
a. heavy metals
b. mercury
c. nervous
Here you will find a summary of the content from the
previous activities:
The mass of an atom is determined by the masses of the
protons and neutrons found in its nucleus, therefore the
mass of an element is proportional to the atomic number
of said atom.
The unit used to measure the mass of atoms is known as
atomic mass unit.
The ability of substances such as salt and sugar to
disintegrate in a liquid is called solubility. This ability is
related to the electric characteristics of each substance.
Atoms have the ability to win or lose electrons, becoming
atoms with an electric charge that can be negative or
positive. These atoms are known as ions. The chemical
ties in which electrons are won or lost are called ionic
bonds.
The association of two ions joined to water molecules in a
solution is known as an ionic pair.
The ions perform an important function transmitting
information between the neurons, as they allow the
generation of nerve impulses, thanks to the changes in the
concentrations of positive and negative charges inside and
outside the cell.
Assignment/
homework
The teacher
present the
homework
Some chemical elements are key to the biological
processes of living beings; however, the elements known
as heavy metals, which are used to make industrial and
daily use elements, are toxic.
The following activity deals with Skill 5 and allows
students to strengthen their knowledge about the impacts
of heavy metals on the environment and the health of the
living beings. To do so, it is necessary that the students
have examined and understood the contents from Activity
3.
1.
On your notebook, write a list of five object that
contain heavy metals and that you have contact with,
either at home, on the street, or at school. You can use
the following chart as a guide:
Name of the
object
Use of the
object
Where is
it?
Heavy
metals
2.
Once you have the list, join two classmates.
Between the three, choose one of the objects. It can be a
common object that you all have on the lists, or just one
that calls your attention.
3.
Inquire about the proper disposal of the chosen
object after it has been used. Bear in mind the following
questions: Where should it be disposed of? Which
precautions should be taken into account for its
manipulation? Who or what company picks it up to prevent
it from polluting the environment?
Evaluation/
Assessment
Evaluation
4.
To finish, choose a spokesperson from the group to
share your answers with the rest of the class.
The following evaluation aims to allow the student to
review the concepts, and chemical and biological
processes exposed throughout the learning object. In
order to be successful, it is necessary that the student has
previously revised each activity of the unit, understood
each visual resource, and done the proposed learning
activities.
On points 1 to 5 you will find some definitions. Read them
closely and write the corresponding concept that relates to
each one of them.
1. Unit used to measure the mass of atoms.
2. Atom with a charge that can be negative or positive.
3. Substance dissolved in a solution.
4. Substance dissolved in another substance.
5. Association of two solute ions bonded to solvent
molecules in a solution.
Answer:
1. Atomic mass unit
2. Ion
3. Solute
4. Solvent
5. Ionic pair
Classify the statements 6 to 9 as true (T) or false (F).
6. The mass of an atom is proportional to the number
of protons and electrons in its nucleus. (
)
7. Salt is a non-ionic substance because its atoms have
covalent bonds. (
)
8. Gold mining in Antioquia does not include processes
that negatively affect the environment. (
)
9. Neurons can transmit information through the
nervous system thanks to the fact that their
membranes do not have any kind of polarity. ( )
Answer key:
6. False. The mass of an atom is proportional to the
number of protons and neutrons in its nucleus.
7. False. Salt is a ionic substance.
8. False. During the process of gold mining they use
mercury, which is a heavy metal that negatively affects
the environment.
9. False. Neurons can transmit information through the
nervous system, thanks to the fact that its membrane
presents polarity.
Glossary
Glossary
Ion: Atom or group of atoms that lose or win one or more
electrons, which makes them acquire electric charge.
Glossary tool
Mass: Physical magnitude that expresses the amount of
matter in a body, measured by its inertia, which
determines the acceleration produced by a forces that acts
upon it and whose unit in the international system is the
kilogram (kg).
Atomic Mass: Relation between the mass of an atom and
1/12 of the mass of a carbon atom.
Ionic Pair: When an anion and a cation stay bonded in a
solution, even if they are electrostatically associated with
the solvent.
Solubility: Ability that a substance has to be dissolved in
another one.
Solute: A body that is dissolved.
Solvent: Substance that can
another homogenous mixture.
Vocabulary
box
Vocabulary
box
dissolve
and
produce
Toxic: Substance that can cause illness or t death, as a
consequence of the lesions produced by a chemical effect.
Atomic Bond: Refers to the electric forces holding atoms
together to form molecules and solids. The attraction
between electrons of one atom to the nucleus of another
atom contributes to what is known as chemical bonds.
Glossary tool
Nerve Impulse: The electrical signal or discharge that
travels along a nerve fiber.
To dispose of: To get rid of something, such as toxic
waste or an object that we are not using anymore.
To sweeten: to make something sweet or sweeter in
taste by adding sugar, honey, or other sweet ingredient.
English
review topic
English
review topic
Taken and adapted from:
- Atomic
bond.
Retrieved
from:
http://www.science.uwaterloo.ca/~cchieh/cact/c120
/chembond.htmlhttp://www.science.uwaterloo.ca/~c
chieh/cact/c120/chembond.html
- Nerve
impulse.
Retrieved
from:
http://dictionary.kids.net.au/word/nerve_impulsehtt
p://dictionary.kids.net.au/word/nerve_impulse
- To dispose. Retrieved from: http://www.merriamwebster.com/dictionary/disposehttp://www.merriam
-webster.com/dictionary/dispose
- To
sweeten:
Retrieved
from:
http://www.merriamwebster.com/dictionary/sweeten
Passive voice with simple present
Bibliography
Bibliography
Alberts, B., Jonson, A., Lewis, J., Raff, M, Roberts, K.,
Walte, P., (2010). Biología molecular de la célula.
Barcelona, España. Ediciones Omega.
Curtis, H., Barnes, N., Schnek, A., Massarini, A., (2008).
Biología. Buenos Aires, Argentina. Médica Panamericana.
Ecured.cu. (2016). Pila eléctrica. Retrieved
http://www.ecured.cu/Pila_el%C3%A9ctrica
from:
Flat World Knowledge. (2016). General Chemistry:
Principles, Patterns, and Applications 1.0. Retrieved from:
http://catalog.flatworldknowledge.com/bookhub/4309?e=
averill_1.0-ch17_s02.
Mathews, C., Van Holde, K. E., Ahern k. G., (2002).
Bioquímica. Madrid, España. Pearson Educación.
Soluciones-quimicas.wikispaces.com. (2016). Solucionesquímicas - home.
Retrieved from: https://solucionesquimicas.wikispaces.com/home
Um.es. (2016). Aula Virtual de Biología. Retrieved from:
http://www.um.es/molecula/gluci04.htm
Vieta, P. (2011). Les aigües; bevem diferents molècules
d’aigua.
Retrieved
from:
https://catquimica.cat/2011/04/04/les-aigues/
YouTube. (2016). Diferencia entre masa y peso. Retrieved
from: https://www.youtube.com/watch?v=XZB924RFXJ8
YouTube. (2016). Disolucion de sal de mesa. Retrieved
from: https://www.youtube.com/watch?v=-HCRm5HX1hc
Yurcanis, P., (2006), Fundamentos de química orgánica.
México. Pearson Educación.
123RF Stock Photos. (2016). Lantanidos. Retrieved from:
http://es.123rf.com/imagenes-dearchivo/lanthanoids.html?mediapopup=24509724
123RF Stock Photos. (2016). Mineral carbón. Retrieved
from:
http://es.123rf.com/clipartvectorizado/mineral_carbon.html