UNIT 3
CLASSIFYING MATTER
1. Classifying matter
2. Separation techniques
Techniques to separate homogeneous mixtures:
 Crystallisation
 Distillation
 Chromatography
Techniques to separate heterogeneous mixtures:
 Filtration
 Magnetic separation
 Liquid decanting
3. Solutions
Concentration
Classifying solutions
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A pure substance is a material that can be represented by one formula. Eg :
H2O, CO2, Au
The atoms that make the substance are bonded. (enlazados, we will study
this concept in the next unit)
There are two types of pure substances:
Elements
Compounds
An element is a pure substance made of only one kind of atom.
Can be isolated atoms . He, Au, Ag.
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Can go in pairs Cl2 or threes O3 or more, but generally they go in pairs.
A compound is a pure substance made of more than one kind of atom.
H2O, CO2, CO, HCl.
A mixture is a material made up of two or more substances that can be easily
separated by physical means.
The substances are not bonded among them.
A heterogeneous mixture is a material in which you can distinguish the
components by a macroscopic approach.
“Hetero” means different, it consists of visibly different substances.
Examples: Pizza, fruit salad.
A homogeneous mixture is a material in which you can´t distinguish the
components by a macroscopic approach.
Language: The stress in the word components is like this components
“Homo” means the same, it has the same uniform appearance and
composition throughout.
Commonly we call the homogeneous mixtures solutions.
Homogeneous mixtures = solutions
Examples: Coca-cola, tea.
SEPARATION TECHNIQUES
There are different techniques to separate mixtures.
Techniques to separate homogeneous mixtures:
 Crystallisation
 Distillation
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 Chromatography
Techniques to separate heterogeneous mixtures:
 Filtration or filtering
 Magnetic separation
 Liquid decanting or liquid decantation or liquid-liquid extraction
You have to complete the next activity to learn the different techniques:
Instructions:
1-Read the texts and underline the words you don´t understand (don´t ask the
meaning of those words yet)
It is used to separate two liquids that are not mutually soluble.( they
don´t mix together)
Eg.: Water and oil
The mixture is poured into a separatory funnel; after a few minutes, the
different components separate. This happens because these liquids don´t
mix and have different densities. The denser liquid goes to the bottom
and the less dense goes to the top.
The stopcock is opened to let the bottom liquid flow into a beaker and
then is closed. The remaining liquid, the less dense, is collected in a
different beaker.
It is used to separate a solid and a liquid which are not mutually soluble.
Eg.: sand and water
The mixture is passed through a filter paper in a filter funnel. The solid
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can´t pass through the filter paper because its particles are bigger than
the holes of the paper, but the liquid particles can pass through the
paper.
It is used to separate magnetic substances from non magnetic
substances.
Eg.: Iron and sand
A magnet is passed through the mixture and attracts the magnetic
substance.
It is used to separate a solid from a liquid. The solid and the liquid are
mutually soluble.
Eg.: salt and water
The solution is heated and left to evaporate. As the liquid evaporates the
solid falls to the bottom of the beaker and forms crystals.
It is used to separate two liquids which are mutually soluble.
Eg.: Alcohol and water.
The solution is heated. The liquid with the lower boiling point evaporates
first. The vapour passes through a condenser where it cools down and
condenses into a liquid, this liquid is collected in the beaker.
The liquids separate because they have different boiling points.
It is used to separate the colours of the ink or the pigments of plants.
We put a sample of the solution on a filter chromatography paper, we put
it in a solvent (water and alcohol for example),this solvent is called the
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eluent. The eluent rises and solves the sample. Due to the different
solubility of the different components of the ink, they go up at different
rates so we can separate them.
2-You are going to watch to a video explaining a technique. While you are
listening write down the name of the technique and all the new words that you
hear and then identify and label the text above that explains that technique.
Repeat the same stages with all the techniques
Technique
Key words
Video
nº1
Video
nº2
Video
nº3
Video
nº4
Video
nº5
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Video
nº6
Language:
NOUN
INFINITIVE
GERUND
Decantation/Decanting
To decant
Decanting
Filtration/ Filtering
To filter
Filtering
Both crystallisation and crystallization are posible.
Another example of this type of word is: colour or color.
Language:
Apparatus is uncountable, if you want to refer to an item you have to say “ a
piece of apparatus”. (Instrumental)
Other synonyms are: lab instruments or devices. But both are countable.
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APPARATUS and ACTIONS
to
to
to
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APPARATUS and ACTIONS
WATCH GLASS
VIDRIO DE RELOJ
CONDENSER
REFRIGERANTE
ROUNDBOTTOMED
FLASK
MATRAZ DE
FONDO
REDONDO
SEPARATORY FUNNEL
/SEPARATING FUNNEL
EMBUDO DE
DECANTACIÓN
FILTER FUNNEL
EMBUDO DE
VIDRIO
FILTER PAPER
PAPEL DE FILTRO
TO HEAT
CALENTAR
TO POUR
VERTER
SPATULA
ESPÁTULA
TO STIR
AGITAR
STIR ROD
VARILLA
AGITADORA
MAGNET
IMÁN
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SOLUTIONS
A solution is a homogeneous mixture that can be easily separated by physical
means.
It is composed of solute and solvent.
Concentration of a solution
Concentration of a solution is the amount of solute dissolved in a given amount
of solution at a given temperature.
Language:
In Chemistry the structure “in a given amount of ..” is so common. (en una
cantidad dada de…)
Other similar expressions are:
Given that…
Ex: Given that all the reactants are gases, we can measure the
volume with one formula. (Dado que…)
At a given…
Ex: We measure the solubility at a given temperature (A una
dada….)
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We can classify solutions in two types:
• Dilute solutions, contain a low amount of solute.
• Concentrated solutions, contain a high amount of solute.
When we add the highest amount of solute that the solvent is able to dissolve,
we have a saturated solution.
Saturated solution is a solution that contains as much solute dissolved as
possible.
Language:
ADJETIVE
VERB
VERB
Infitnitive
Past
Dilute solution
To dilute
Diluted
Saturated solution
To saturate
Saturated
Concentrated solution
To concentrate
Concentrated
We can also classify solutions in :
Solute Solvent Example
solid
solid
alloys
(aleaciones)
solid
liquid
Salt in water
liquid
solid
amalgam
(amalgama)
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liquid
liquid
milk
gas
liquid
Oxygen in water
gas
gas
air
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Ways to express the concentration of a solution:
Concentration =
Concentration
in C m/v =
mass/volume
g/l ; Kg/l ;
g/ml...
ACTIVITIES
A1- Classifying matter.
Draw using the kinetic theory and different colours:
a)A mixture of water and salt.
b)An element .
c)A compound .
d)A solution of three elements.
e) An element (each particle has three atoms).
f) A compound (each particle has three atoms).
g)A solution of two compounds.
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A2-Classifyng matter
Complete the table as in the example:
Picture
Description
This is a homogeneous mixture of two elements. One of
them has two atoms and the other has one atom
This is a heterogeneous mixture of an element of two
atoms and a solution of one compound of two atoms and an
element of one atom
This is a heterogeneous mixture of two compounds. One of
them has two types of atoms and the other has three
types of atoms.
A3-Parroting.
A4- Separation techniques
Name the separation technique shown in each picture:
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A5- Separation techniques
Work in pairs:
1.Write the description of two techniques using examples, for example
ink...
You can use the following chart:
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What material I am Which apparatus I am Which actions I will do
going to separate
going to use
NAME
NAMES
Ink
Filter paper
To introduce
Eluent
To place, to put
VERBS
Beaker
DESCRIPTION
To separate the ink I am going to put a sample of the ink in the bottom
part of a filter chromatography paper then I am going to put the filter
paper in the eluent. The eluent will dissolve the different components of
the ink and they will rise at different rates through the filter paper, so
that they are separated.
What material I am Which apparatus I am Which actions I will do
going to separate
going to use
NAME
NAMES
VERBS
DESCRIPTION
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What material I am Which apparatus I am Which actions I will do
going to separate
going to use
NAME
NAMES
VERBS
DESCRIPTION
2. Take it in turns to read your description to your partner
3. Your partner has to guess which technique you are describing.
A6-Solutions.
Calculate the concentration of a solution made by mixing 2g of salt and 10 ml of
water
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A7-Solutions.
You dissolve enough sugar in 2 litres of water to obtain a 10 g/l solution. How
much sugar have you dissolved?
A8- Review (Writing and speaking activity)
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A9-Review: Bingo activity
Write 16 of the following words in the table below
PURE SUBSTANCE
ELEMENTS
COMPOUNDS
MIXTURE
HETEROGENEOUS
MIXTURES
SOLUTIONS
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DECANTING
WATCH GLASS
FILTERING
FILTER PAPER
MAGNETIC SEPARATION
THERMOMETRE
CRYSTALLISATION
DISTILLATION
CHROMATOGRAPHY
TO HEAT
TO POUR
SPATULA
CONDENSER
SEPARATING FUNNEL
TO STIR
FILTER FUNNEL
MAGNET
STIR ROD
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EXERCISES
1
2
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3
4
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5
6
We prepare a solution of water and sugar. We add 2,5 grams of
sugar to 50 mL of water. The solution has a volume of 51,5 mL.
Calculate the solution concentration in g/L
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7
How many grams of Br2 are needed to make 250 mL of a 4.5 g/L
solution?
8
The concentration of a solution of ClK is 24,5 g/L. Calculate the
solute mass, in grams, that you will find in 750 ml of this solution.
9
10
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11
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LABORATORY ACTIVITY
Making solutions
You are going to prepare 100 ml of a solution of sugar and water. We want a
concentration of 50 g/l.
1. Write the formula for the concentration of mass/volume
2. Substitute the data in the formula
3. Work out the mass of sugar
Before adding the sugar you have to weigh the sugar. To weigh the sugar you
have to reset the watch glass.
Now you have all the data that you need to prepare the solution.
To prepare 100 ml you have to use a volumetric flask of that volume.
First you have to introduce the solid. You can do it dissolving the sugar in a
volume of water smaller than 100 ml, (for example 50 ml). Then you introduce
the solution in the flask.
After that, you fill the flask with water up to the line.
The lower part of the water has to touch the line of the volume that you are
measuring.
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You can do the final part with a dropper. Draw three pictures that explain, how
you do it:
Working with this solution.
Let´s calculate the density of the solution
Write the formula for the density:
Choose a volume between 0 and 100 ml and write it:
Measure this volume with the cylinder.
Put a beaker on the scale and reset the scale. Then measure the mass of the
solution that you have taken.
M=
Calculate the density using the formula:
Questions:
If we take 50 ml of this solution, how much sugar is contained in it?
If we take 50 ml of the solution, how much mass will it have?
What volume of solution will contain 3 g of sugar?
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GLOSSARY:
alloy [ˈælɔɪ]
amalgam [əˈmælgəm]
bond [bɒnd]
chromatography [ˌkrəʊməˈtɒgrəfɪ]
crystal [ˈkrɪstl]
decant [dɪˈkænt]
dilute [daɪˈluːt]
distillation [ˌdɪstɪˈleɪʃən]
element [ˈelɪmənt]
formula [ˈfɔːmjʊlə]
funnel [ˈfʌnl]
heterogeneous [ˈhetərəʊ'd[zh]i:nI&s]
homogeneous [ˌhɒməˈdʒiːnɪəs]
mixture [ˈmɪkstʃər]
pour [pɔːr]
pure [pjʊər]
soluble [ˈsɒljʊbl]
spatula [ˈspætjʊlə]
stir [st3ːr]
substance [ˈsʌbstəns]
technique [tekˈniːk]
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