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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.

They can be isolated atoms: He, Au, Ag.

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Or they can be in pairs, Cl2, or threes, O3, or more, but generally they are

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.

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APPARATUS and ACTIONS

to

to

to

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APPARATUS and ACTIONS

WATCH GLASS

VIDRIO DE RELOJ

CONDENSER

REFRIGERANTE

ROUND-

BOTTOMED

FLASK

MATRAZ DE

FONDO

REDONDO

SEPARATORY FUNNEL

/SEPARATION FUNNEL

EMBUDO DE

DECANTACIÓN

FILTRATION

FUNNEL

EMBUDO DE

VIDRIO

FILTER PAPER

PAPEL DE FILTRO

TO HEAT

CALENTAR

TO POUR

VERTER

SPATULA

ESPÁTULA

TO STIR

AGITAR

STIRRING ROD

VARILLA

AGITADORA

MAGNET

IMÁN

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SEPARATION TECHNIQUES

There are different techniques to separate mixtures.

Techniques to separate homogeneous mixtures:

Crystallisation

Distillation

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 separation 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.

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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

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.

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It is used to separate the colours of ink or 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

eluent. The eluent rises and dissolves 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 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

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Video

nº5

Video

nº6

Language:

NOUN INFINITIVE GERUND

Decantation/Decanting To decant Decanting

Filtration/ Filtering To filter Filtering

Both crystallisation and crystallization are possible.

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.

SOLUTIONS

A solution is a homogeneous mixture that can be easily separated by physical

means.

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It is composed of solute and solvent.

Concentration of a solution

The 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 quite 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….)

We can classify solutions in two types:

• Dilute solutions, contain a low amount of solute.

• Concentrated solutions, contain a high amount of solute.

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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

Infitnitive

VERB

Past

Dilute solution To dilute Diluted

Saturated solution To saturate Saturated

Concentrated solution To concentrate Concentrated

We can also classify solutions as:

Solute Solvent Example

solid solid alloys

(aleaciones)

solid liquid Salt in water

liquid solid amalgam

(amalgama)

liquid liquid milk

gas liquid Oxygen in water

gas gas air

Ways to express the concentration of a solution:

Concentration =

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Concentration in

mass/volume

C m/v =

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 seen 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-Solutions.

Calculate the concentration of a solution made by mixing 2g of salt and 10 ml of

water

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A6-Solutions.

You dissolve enough sugar in 2 litres of water to obtain a 10 g/l solution. How

much sugar have you dissolved?

A7- Review (Writing and speaking activity)

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A8-Review: Bingo activity

Write 16 of the following words in the table below PURE SUBSTANCE

ELEMENTS

COMPOUNDS

MIXTURE

HETEROGENEOUS

MIXTURES

SOLUTIONS

DECANTING

FILTERING

MAGNETIC SEPARATION

CRYSTALLISATION

DISTILLATION

CHROMATOGRAPHY

CONDENSER

SEPARATION FUNNEL

FILTRATION FUNNEL

WATCH GLASS

FILTER PAPER

THERMOMETRE

TO HEAT

TO POUR

SPATULA

TO STIR

STIRRING ROD

MAGNET

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EXERCISES

1

2

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3

4

80

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 by dissolving the sugar in a

volume of water smaller than 100 ml, (for example 50 ml). Then you introduce

the solution to the flask.

After that, you fill the flask up with water, to the line.

The lower part of the water has to touch the line of the volume that you are

measuring.

You can do the final part with a dropper. Draw three pictures that explain how

you did it:

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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 3g of sugar?

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GLOSSARY:

alloy [ˈælɔɪ]

amalgam [əˈmælgəm]

bond [bɒnd]

chromatography [ˌkrəʊməˈtɒgrəfɪ]

crystallisation [krɪstələˈzeɪʃən]

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]