Chemistry Form One Notes – Matter

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Concept of matter

Concept of Matter

Explain concept of matter

Matter is anything that has mass and occupies space. Therefore, anything around us provided it

has mass and can occupy the space, is termed as matter. Thee are many kinds of mater. Can

‘you mention some? The word matters used to cover all the substances and materials from which

the earth and nivers is composed of. These include all materials around us such as water, sil

plants, animals, ir, clothes, ete.

Any particular kind of matters called substance, Substances include elements and compounds.

‘An element is a substance which isthe limit of chemical analysis. When two or more elements

‘You will earn more about this later

States of matter

‘The Three States of Matter

Describe the thre states of matter

Any chemical substance we study exists in any ofthe three forms (or physical states) The three

ferent states of matter are

2. liquid state and

‘Look around you and name substances that ae solids, liquids and gases. The state in which any

rater exists depends on temperature and sometimes pressure conditions. One substance may

Investigation of the compressibility of solids, liquids and gases

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Findings

The three states of matter differ in their physical properties. These differences in properties are

summarized in table bellow

Differences in properties ofthe three states of matter

Property Physical state

Solid Liquid Gas

no definite shape, takes no definite shape, occupy while

Shape thas definite shape shape ofthe continer ——_contner

variable (depending

Volume has a fixed volume has a ied volume temperature and pressure)

Fluidity doesnot low generally owscasly flows easily

Expansion on heating low motion high

Compresibiiy incompressible almost incompressible highly compressible

Motion of particles slow heh very high

Density igh moderate high ow

Tangibiliy tangible tangible intangible

Visi visible visible invisible

(One State of Matter to Another

‘Change one state of matter to another

We have scen that matter exists in three diferent states – solids, liquids and gases. We can use

the kinetic theory of matter to explain how a substance changes from one state to another.

Basically, changes from one state to another are caused by alterations in temperature and

pressure, Normally molecules, ions or atoms ofa substance move faster when the temperature is

increased

Melting and freezing

Meling is a change from sold to liquid state. When solids are heated, their constituent particles

(atoms, molecules or ions) get energy and vibrate more violently. Vibrations of these particles

overcome (exceed) their binding forces. The particles become mobile. The crystalline structure

of solid is destroyed. A liquid state is reached andthe particles are ice to move. The temperature

at which this happens is called melting pint of the solid.

‘The melting pont ofa solid tells us something about he strength of forces holding its constituent

particles together. Substances with high melting points have strong forces between thet

Tartcles. Those with low meting points have weak forces between thei particles

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Freezing isa change from liquid to solid state. Freezing sth opposite of melting. The proces is

reversed atthe same temperature if liquid is cooled, The temperature at which a substance turns

to a sold is called reecng point The meling point and feezing point of any given substance

are both the same, For example, the melting and freezing of pure water takes place at OFC

Meling is not affected by any changes in atmospheric pressure

Evaporation and boiling

2°

Boiling is a change from liquid to vapour state at particular temperature. Evaporation is the

change from liquid to vapour state at any given temperature. I liquid is exposed to open air, it

evaporates. Splashes of water evaporate at room temperature, After rain, small pools of water dry

up. When a liquid changes into a gas at any temperature, the process is

called evaporation. Evaporation takes places from the surface of the liquid. The larger the

surface area, the faster the liquid evaporates. The warmer the liquid is the faster it evaporates.

Thus, surface area and temperature affects the rate of evaporation ofa liquid

‘When a liquid is heated, its molecules get more energy and move faster. They knack into each

other violently and bounce further apart. As the heating goes on, its molecules vibrate even

faster. Bubbles of gas (due to air dissolved in water) appear inside the liquid. The whole process

is called boiling. The temperature at which a liquid boils i called boiling point

‘The molecules atthe surface of the liquid gain enough energy to avercome the forces holding

them together. They break away from the liquid and from a gas (vapout). As more of the liquid

molecules escape to form a gas, a liquid is said to evaporate. This occurs atthe boiling point of @

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Te temperature at which a liguid boils explains how strong the forces holding its particles

(molecules) together are, Liguids with high boiling points have strong forces of attraction

between their molecules than those liguids with low boiling points

The boiling point of aliquid can change ifthe surrounding pressure changes. Ifthe surounding

pressure falls the boiling point also falls. The boing point of water at standard pressure (760

mmHg) is 100°C. On a high mountain, where pressure is low, it is lower than 100°C. Ifthe

gas when the pressute is either increased or decrease.

‘The melting and boiling points of some common chemical substances at standard

{temperature and pressure (sp)

Physical state at room temperature

Substance evo) Meting point °C) Boing poimt?O)

Oxygen Bs 219 +188

Nitogen ms 210 +196

Ethanol alebol) iguid 7 7

Water Viuid ° 100

Sulphur solid is aa

Common salt (som

chlocide) solid sor ass

Copper sold toss 2600

Carton ide Bs sublimation point (1): -78

From the above explanation, obvious differences between evaporation and boiling can be

detected. See table bellow

Evaporation Boiling

1.Occurs at al temperatures (Occurs atone particular temperature (boiling pst)

2.Occurs on the surface of the iguid ‘Occurs both nse and onthe surface of the guid

3.Takes place slowly Takes pace faster

4 bbls are not necessary formed Bubbles are formed

substance from liquid to gas (vapour) state at any temperature

Boiling is a change in state of a substance from liquid to gas at a particular temperature and

pressure

Condensation and solidification

‘The reverse of evaporation is condensation, Ths is brought about by cooling. When a gas is

cooled down, its particles lose energy. They move more and moe slow. When they knock into

cach other, they do not have enough nergy to bounce away again. They stay close together and

8 liquid forms, This process is called condensation, When the liquid is cooled further, the

movement of the particles slows down even more. Eventually, they stop moving and a solid

forms Tiss called sliication

Condensation can be defined as a change in state of a substance from gx8 (vapour) to

liquid. Solidjcation isa change fom liquid to sold state ofa substance. Solidification isthe

same as freezing

Sublimation

‘A few solids do not melt when they are heated. Instead, they change dretly from the slid to

xscous sate without passing through the liquid. state, This change in stale is

called sublimation, When a solid changes directly into gas, iti sid to sublime. lodine, solid

carbon dioxide (dry ice”) and ammonium chloride are examples of solids that sublime, Like

‘melting, sublimation also occurs at one paricular temperature foreach pure solid

The Importance of Changing One State of Matter to Another

Explain the importance of changing one state of matter to another

The following points summarize the importance of change in stat:

1, Separation of mixtures

Dierent-mixtures can be separated though such processes as distilation, sublimation,

evaporation and condensation. Let us have a look at an example of disillaion, This process

involves boiling, evaporation and condensation. Distillation as a process can be applied in

separation of mixture (solution) of two or more subsances. A mixture of two oF more

substances with different boiling poins e.g. water and alcohol canbe separated by this mean. In

sucha case, a container with the mixed-up liquids is heated. The liquid with alow boiling point

evaporates and condenses first, leaving the one with a high boiling point in the container. The

distillate (liquid with low boiling point) i collected, cooled down and transfered into another

2. Industrial manufacture of products

Industrially, the process of distillation is applied in the production of pure substances such as

beer and other alcoholic drinks such as wine, vodka, Konya, ete, The manufacturing process

3. Refining of petroleum (crude oil)

‘Crude oil contains organic liquid components, each with a different boiling point. In the refinery,

the components with lower boiling points evaporate first and get separated out, leaving those

‘ith higher boing poins behind. In this way, we get various types of ol components actions)

suchas petrol, diesel, kerosene, lubricating ol, te

4, Drying of crops and clothes

When you suspend your clothing on a cloth line to dry, the moisture init is lost trough

evaporation. Likewise, farmers inthe village often spread crops on the ground to dry. They do

this in order to reduce moisture content and hence prevent decaying, The moisture contained in

important in everyday lives.

5. Cooling of our bodies in hot weather

You al ike to drink cold water or beverages especially during hot weather, You can use a

reftigestor to cool down drinking water or beverages direcly. Allematively, you can feeze

‘ater into ice and then use the resulting ce for cooling the beverage. ce blocks are also saleable.

Moreover, one can car some money if she freezes water into ice blocks and then sells them to

beverage vendors Perishable products such s fish, meat, milk, te are often packed in ce blocks

to prevent them fiom gong bad. ce 38 we studied early, is formed when water feezs (a change

in state om liquid wo solid).

6. Ice formation in refrigerators

‘You all like to drink cold water or beverages especially during hot weather. You can use a

refrigerator to cool down drinking water or beverages directly. Alemaively, you can Feeze

water into ice and then use the resulting ice for cooling the beverage ce blocks are also saleable.

“Morcover, one can earn some money if she freezes water into ice blocks and then sll thems to

beverage vendors. Perishable products such as fish, mea, milk, tear often packed in ice blacks

to prevent them fom gong bad ee 38 we studied early, i formed when water feezes (a change

in state from liquid to slid)

7. Melting metals to make alloys

In metallurgical industries, need may aise to mix two oF mote metals (alloys) together. This is

only possible, where two or more metals are first melted a high temperature into liquids. Then

the resulting liquid metals are mixed in appropriate proportions. This is followed by cooling

down th mixture to a sli alloy. Normally alloys have beter qualities than individual metals

8. Testing the purity of substances

The presence of impurity may ows or raise the boiling point of the substance. A pure substance

relts and boils at definite temperatures (See table $4). The values forthe melting point and

boiling point are precise and predictable. This means that we can use them to test the purity of a

sample. They can also be sed to check the identity of unknown substance.

Atypical example

Sea waters impure. It ieezes at temperature well below the freezing point of pure water (0)

and boils ata temperature above the boiling point of pure water (100°C). Other substances

bchave in a similar manner. So boiling a a change in state can be used to test forthe purity ofa

substance.

In addition, the impurity also reduces the exactness ofthe melting or boiling point. An impure

substance melts or boils over range of temperature, not at a patcular point

Meling and boing poins of some pure substances

Substance Meling point °O) Boiling point (0)

Water ° 100

thao! 117 *

Oxygen 20 183

Sodium os 0

Sulphur 19 4s

ron 1540 2900

Diamond 3550 4832

Cobalt re 2900

Nitrogen 210 196

Propane Iss 2

Ethane acid 16 nis

9. Formation of rain

Perhaps the most important ofall, as far as change in state is concerned, is the formation of rain

Rained is mainly formed through the process of evaporation and condensation, Water vapour,

evaporating mostly from water bodies (oceans, seas, lakes, rivers, ponds, ete), land and plants

rises upto the sky. Asi rises, it cools down and condenses into tiny droplets

(On further cooling as they ise up, these droplets form bigger water drops. Owing to gravitational

force, these drops fall down as rainfall. Every one of you knows how important ran is to our life

Therefore, you have noticed how evaporation and condensation, as changes in state, contribute to

rain formation.

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Kinetic nature of matter

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patcles of substance can etemine the properties of tha substane, nd parca the sate

3. Heavier particles move more slowly than lighter particles at the same temperature

4. Each substance has unique particles that are different from the patticles of other

substances

5. ‘The particles of matter are held together by strong electrostatic forces,

6. There are empty spaces between the particles of matter that are very large compared to

the particles themselves

‘The solid state

In the solid state, the particles are so closely packed (see figure bellow. The particles are held

together by strong forces of attraction that act like a chemical glue. Free movement of particles

cannot take place. They cannot move around freely inthis arrangement. Instead, they vibrate

about a fixed position. They are arranged in a fixed pattern which form a cluster of vibrating

‘masses. This makes a solid to have a fixed shape, which cannot be changed except by applying

strong extemal frees.

‘The liquid state

“The particles of aliquid are also closely packed but the forces of attraction between them are

‘weaker than ofa solid. These forces of attraction tend to bind them together. The particles have

‘more kinetic energy and they can move around each other. The binding forces are strong when

particles come close to one another. It is thought thatthe particles ofa liquid are fairly randomly

arranged but consist of “clusters” closely packed together. Ths property makes a liquid to have a

<efinite volume. However, since the particles are fairly free to move a liquid does not have any

characteristic shape (see figure §.5(b). Thus, liquid will always take the shape of ts container

‘The gaseous state

The gaseous state is one in which the particles are moving independently of each other in all

directions and at great speeds. The particles ofa gas are relatively far apart, They exert no force

of attraction on each other. They have more energy than the particles of solids and liquids. They

‘move rapidly and randomly, colliding with each other and with the walls of the container. A

found to be approximately 500 ms

It hasbeen estimated thaw nitvogen molecule makes collisions each second, Ths, a gat will

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(a) sold state) liquid state (6) gasstate

Physical and chemical changes

Depending onthe nature of change, ll changes that mater undergoes canbe classified as either

phytic o cena

‘The Characteristics of a Physical Change

Physical change

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Physical Changes of Matter Experimentally

Demonsrae physical changes of mate experimentally

Experiment

solid form

‘You will have seen that all the above changes involve only changes in physical forms ofthe

substances. The chemical nature of substances remained unchanged, Therefor, we ean define a

Physical change asa change that doesnot involve formation of new substance but involves a

change in state o physical form ofthe substance and that such a form canbe reversed

The Characteristics of a Chemical Change

Chemical change

Some changes that materials undergo are permanent. Such changes usually involve changes in

chemical properties ofa substance. For example, when you bum a piece of wood in fie, you get

ash The properties of wood and ash are very different. There is no way you can change ash back

to wood. tis practically imposible. A permanent change in chemical properties ofa substance

is called a chemical change. In a chemical change, a substance losses all its physical and

chemical properties

Characteristics

Includes

ditferen chemical and physical properties as compared othe orginal substance

3. There isa change in weight or mass ofthe substance undergoing the change. When you

of heat must be supplied

Chemical Changes of Matter Experimentally

Demonsirate chemical changes of matter experimentally

Experiment

witha blue lame. If you continue heating it gradually decreases in amount and Finally the spoon

ivitatng smel. The gas can also be detected by buring the sulphur ina gas jar to which some

be litmus solution has been added. The gas formed, sulphur dioxide, will tum the blu litmus

Table

Differences between physical and chemical changes

Physical change Chemical change

1. Produces 0 new kind of mater ‘Always produces a new kind of mater

2. There is substantial change in the weight

2. There is no change is mass or weight ofthe substance subtance

3. The change canbe revered 3. The change canna be revered

4. Lite heats absorbed o evolved 4 Heatchanges may be large

substan 5. oth pysieal and hema properties ae chaff

Elements and symbols

‘The Concept of an Element

(ur world and universe are made up of millions of different substances. We have already seen

how these substances can be clasifed into solids, liquids and gases However, on close

«examination, we find that these substances are made up of @ number of small elements,

‘An element can be defined as a substance that cannot, by any known chemical process, be split

into two or more simpler substances. This means that elements cannot, by any chemical process,

bbe made to yield substances simpler than themsclves, An clement isa substance because it has

the same composition throughout

In 1803, a scientist called Jobn Dalton suggested that each element was made up ofits own kind

of particles. He called these particles the ‘atoms’. Therefore, an element is a substance that is

‘made up of only one kind of atoms

Names and Symbols of Elements

A chemical symbol is the way of representing an element using initial letter(s). There are many

different elements as you have seen above. Every element has a name and a symbol to represent

it, Some symbols are just a single capital letter, such as H. Others have two letters, the first of

‘Which is always a capital, such as Mg,

Rules for assigning chemical symbols to elements

Includes

1. Bach element is given a different symbol to represent it

2. Some elements are represented by two letters e.g. Ca (for calcium), Cl (for chlorine), ete

3. Iftwo letters represent the element, the frst letter is always a capital and the second letter

is always a small letter e argon (Ar) and helium (He)

4, Im order to avoid confusion, some elements have their chemical symbols derived from

Latin names

Al symbols are recognized and are used by all scientists all over the world, Some examples of

clements and thei symbols are given inthe table below

Names and Symbols of some Elements

Element Symbol Element Spmbot

Aluminio Al rmine Br

Copper cu Carbon ce

Iron Fe Chlorine a

Lead Pb Hydrogen 4″

Magnesium Me Nitogen N

Mercury Hg Oxygen °

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Potasiom k Phosphorus P

Silver As Sulphur s

Sodium Ne Sitcon si

Cate co Iodine 1

Manganese Mo Flue F

Tia Se oid Au

trou ce

Zine %

Nickel Ni

{is easy to remember thatthe symbol for aluminium is Al, and for carbon is C. But some

symbols are harder to remember because they are taken from Latin names. For example,

Latin name Natrium. See the complet list in te following table.

Elements with Latin names

English name Latin mime Chemica symbot

Gold Arum Av

Potassium Kalam K

Mercury Hydragyrum He

Siner Argent Ae

Ansiony subiam sb

Lead Plums

Ta ‘Stannum Se

Iron Ferm Fe

Copper Copeum co

Tungsten Wolfam w

‘The reason for assigning some elements with Latin names was to avoid confusion among

scientists when representing different elements. For example, the symbol for silicon is Si. It

could be impossible to represent silicon by the symbol S and at the same time represent the

clement sulphur by the very symbol, S. Similarly, potassium could not be represented by the

symbol P that was assigned to phosphorus. So in order to avoid such confusion, scientists

decided to use Latin names to represent some elements. In so doing, the anticipated and

“unnecessary contradiction among scientists from different parts ofthe world was avoided.

‘Symbols are particularly useful when more than one atom is present in substance. For example,

hydrogen gas consists of pais of hydrogen atoms joined together. So hydrogen gas is shown as

1H, When more than one atom is joined together like this, we call the substance formed a

molecule. Atoms making up gases such as hydrogen, oxygen, nitrogen, ete, always exist as

‘molecules. Sulphur exists as a hexagonal ring of eight atoms. Phosphorus exists as a tetrahedron

of four atoms, Table bellow shows some elements that exist as molecules,

Elements that exist as molecules

Element Atomic symbol Molecular symbol

Oxygen °

Nawogen N

Hydrogen 4″

Sulphur s

Phosphorus P

Chlorine cl

rine F

Bromine Br

Iodine 1

Classification of Elements

Elements can be classified as either metas or non-metals. Metals and non-metals have different

physical and chemical properties. Ths isthe criterion used for classification of these elements

into metals on one hand and non-metals on the other hand. Table bellow summarizes the physical

and chemical properties of some common elements.

Properties of some common elements

Date of Metal or non- Solid, guid Melting Boiling Dersiy( fe

Element discovery metal? orgas? oim (°C) poi?C)—— m3)

Oxygen 1774 Non-metal Gas 209 “19 0.00132

Nivogen 1772 Non-metal Gas 210 196 00117

CCasbon Ancient Non-metal Solid 3500 4927 2

ron ims Met Solid 140 3000 9

Copper Ancient Meal Solit 1080 2500 90

Lead Ancient Meal Solid a7 im 13

Gold Ancient Meu Solid 1060 2700 193

Siler Ancient Meal Solid 961 20 os

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Hykogen 1766 Nowell | Gas 29 as «00008

Aluminium 1925 Mel soit «a 2450 n

Tie 16 Mel sid a9 so u

Mercury Ancient Meta Lagu 2» 397 ne

fotine 1 Novel | Gas us 9 4

Chine 1774 Nowmel | Gas so as ooo

Sodium 1807 Mel st * 0 os

ous 1807 Mel sold o “0 086

Sulphur Ancient Nowa Sal us au a

Phospons 1669 Nonetal Slit “ 280 18

Metals and non-metals

There are 94 naturally occurring elements. Some of them are very rare. Francum, for instance,

fas never been seen, The radioactive metals neptunium and plutonium, which we make

antici in quite large amounts, only occur in very smal (trace) quantities naturally. Most of

the elements can be classified as metals. The rest are non-metals. To understand these elements

teiter, refer tothe Periodic Table of Element atthe back ofthis book. Classification of elements

ito metals and non-metals is based on differences between thei physical and chemical

properties, Differences between metals and non-metal re shown in table below

The differences between Metals and Non-metals

A. Physical properties

Mistures Compounds

7”

1. The components ofa mistre canbe separated

by physical means, © fering, magnetic The componcas of «compound can he separated by chemical meds

separation, decantation, ete only

2. The composition of a mixture can vary Compounds are fixed in their compositions by mass of clemelfs

widely, eg. a mixture of 203 of sand with Ip of present eg. there are always? atoms of hydrogen oI atom of oxy

saltor vce vera, ina molecule of water

3. Mixing is not usually accompanied by

extemal effects such as explosion, evolution of Chemical combination i usually accompanied by one or more of th

heat, volume change (or gases) foes

4. Properties of a mixture are the sum of the The properties of compound are quite different fiom those of

properties of the individual constituents of the constituent elements For example, water is a guid whereas fl

muta ‘constituent elements, hydrogen and oxygen, are both gases.

5. No mew substance is produced asthe mixture

forms ‘Anew substance i always produced when a compound forms

B. Chemical Properties

1. Give basic oxides, hai, oxides which react with cis Give acc ides, that i, oxides which react with base

2 Replace hydrogen in acids wo form sats ‘Do ot react with acids in this manner

3. Form postive (+ ions Form negative (ons

4 Form lectrovalent chlorides which ate stable in water Frm covalent chlorides which eact with water

5. Do not react with hydrogen Form stable compound with hydrogen

Elements from Other Substances

Differentiate elements from other substances

There are over 10S different elements known. OF these, 90 have been obtained from the Earth’s

crust and the atmosphere, and 15 have been artificially made by scientists. From this small band

of elements, all other substances on earth are made. Table 5.6 shows the approximate percentage

composition by mass of the elements in the earth’s erust, the oceans, and the atmosphere. Can

you notice the abundance of oxygen? Analysis of the earth’s crust, the oceans, and the

atmosphere reveals that oxygen is the most abundant element on earth, accounting for half the

total mass

Percentage by mass of elements inthe earth’s crust, oceans and atmosphere

Percentage by mass of clement in the Percentage by mass of clements in Percentage by mass af clement in

carth’s crust ‘the oceans atmosphere

Oxygen ” oxygen %6 Nitrogen 1s

Silicon 2s Nitrogen 109 Oxygen ey

Aluminium 78 Chlorine is Argon rr

on 45 Sodium 10 Hydrogen od

Cate 35 Magnesium on Caton oa}

Sodium 25 Cakium 005 Other oa) od

Potassium 25 Sulphur 005

Magnesinn 20 Psasium 008

Tian 0S Niogen 002

Hyogen 02 Bromine 001

Carton 02 Catton oo

Orbe) 13 Otiers xa) oo

Compounds and mixtures

‘Compounds and Mixtures

‘A compound isa substance that contains two or more elements chemically combined together. A

mixture is something that contains two or more elements not combined chemically. Its always

<ificult to identify a mixture from a compound, Before going any further into this topic, let us

start by looking at the differences between compounds and mixtures. These differences are

summarized inthe table below

Differences between mixtures and compounds

Miatures Compounds

1. The components of mixture can be separated

by physical means, eg. firing, magnetic

separation, decantation, te The components of compound can be separate by chemical meso

2. The composition of «mixture can vary widely, Compounds are fixed i their compositions by mass of elements

2 aminture of 20g ofsand with Ig ofsltor vee eg. there are always 2 atoms of hydrogen 1 1 atom of oxy in

ver molecule of water

5. Mixing isnot wlly accompanied by extemal

effects such as explosion, evolution of eat, of Chemical combination i usually accompanied by one or more fF th

‘volume change (or gases) effets

4. Properties of & mixture are the sum of the The properties of a compound are quite different from ths of

roperics of the individual constituents of the constituent clements. For example, water is» hguid wheflas

mixture constituent clemens, hydrogen and oxygen ae both gases.

5. No new substance is produced as the mixture

foams ‘Anew substance is always praduced when a compound forms

‘A Binary Compound

Prepare a binary compound

‘A compound is substance that contains two or more elements chemically combined together.

‘This is a very important difference from mixtures, Mixtures can contain more than one element

but the elements are not chemically combined. The number of chemical substances known is

approximately four millions. All compounds on earth are made from about one hundred simple

‘materials. Such compounds range from simplest substances, like water, which contains only two

elements, to those complex materials of which our own bodily issues are composed. The

following sa short ist of common compounds and the elements they are made of

The Properties of a Compound with those ofits Constituent Elements

‘Compare the properties ofa compound with those of its constituent elements

Elemental composition of some compounds

Compound Content ements

‘tar catbon,byrogen and oxygen

Sou clr common st) sodium and clrine

Mable acum aonate) cali catbon and oxygen

Spi aid ‘ydrogen, sulphur and onsen

ty slums, oxygen and hydrogen

Compounds have different properties fom the elements that make them up. For example:

The Concept of a Mixture

‘A mixture is something that contains two or more substances not combined chemically. The

substances may mix up completely or they may remain separate,

(Our environment is a mixture ofall forms of matter. For example the earth’s crust isa mixture of

soils, rocks, minerals, and water. Sea river, and lake waters contain dissolved gases, living

organisms and, sometimes, salt Air consists of gases, water vapout, and dust particles. The

components of each ofthese mixtures could be elements such as oxygen, nitrogen, sulphur or

gold, Altematively, the mixture might consist of elements and compounds such as hydrocarbons

(eg. petroleum), water, metallic oxides or salts

Other substances that can form mixtures when placed or mixed together include sand and sugar,

‘maize and bean seeds, soil and table salt, water and mud, ete

Mixtures into Solutions, Suspensions and Emulsions

Classification of mixtures

“Mixtures canbe classified as solution, suspensions or emulsions. This classification is based on

whether the mixed substances dissolve completely or not. It also depends on the nature of the

‘mixtures that result upon mixing, Let us look a each category in detail

Solutions

{A solution is a uniform mixture of two or more substances. Such mixtures may be a solid in a

liquid, aliquid in Viquid, aliquid in a gas and, very rarely, a gas in a gas (See table bellow),

We most often think ofa solution as being made of a solid dissolved in aliquid. For example,

solutions of sugar or salt in water are quite common. A solid that dissolves ina liquid is called

solute while the liquid in which that solid dissolves is called a solvent. For example, sugar and

However, other substances that are not normally solids ean be found dissolved ina liquid. For

example, the gases, carbon dioxide and oxygen, dissolved in water are important for lie 10

continue in oceans, seas, lakes, rivers, et.

(dissolves) completly with water. Bet, wine and whisky do not separate int layers of aleobl

sisi, tha, i they make a soiion,

Examples of types of solutions.

Sats

send Lig Gas

ephhlne slowly sublines Orpen an oe

Sasee (ups) in wae nt | Ethno lst in waren vrios | Caton dein walle

tigi sin water Iydocurons in cach ther (petoleun) (carbonated water)

Dry geo coe a pin

Solvents Sold Steslandather met alloys wax Hydogen in wale

Suspensions

it the mixture is left undisturbed, the sold particles wil slowly settle to the batom of the

Muddy water isa typical suspension. The mud woul ste after time i left undisturbed

woud pas hough

IF you mix flour or chalk dust in water, it forms a suspension. Their particles are simply

dispersed (spread) throughout the water and would eventually settle down to the bottom of the

vessel if left undisturbed for sometime,

Differences between solutions and suspensions

Solutions Sispensions

Homogeneous Heterogeneous

Transparetclear Opagueinat cleat

Panicles completely dissolved Panicles separate on standing

Components separated by evaporation Components separated by flan

Emulsions

‘An emulsion is a cloudy mixture of tiny droplets of one liquid suspended in another liquid.

Sometimes two immiscible liquids will not separate out into two layers when mixed together.

One of the liquid may form droplets and spread throughout the other to form

an emulsion, Cooking oil and water do not mix but they will form an emulsion when they are

mixed and shaken. Droplets of oil will spread throughout the water. Unlike pure liquids,

emulsions are cloudy (opaque). So you cannot see through them. The emulsion will not setle

like a suspension. Which other liquids you know can form suspensions?

Formation of mixtures

“Mixtures can be formed from different substances in two major ways,

“The first type constitutes homogenous mixtures, where the substances are totally mixed together

uniformly. Examples include solutions of salts and sugars in water.

‘The second type constitutes heterogeneous mixtures, where the substances remain separate and

fone substance is spread throughout the other as small particles, droplets, or bubbles. All

emulsions and suspensions fll under this category. Examples include suspensions of insoluble

solids or oil droplets in water.

Separation of mixtures

To make use ofthe material around us, we need methods for physically separating the many and

substances is that it is usually posible to separate the constituents by physical means. There are

‘many different physical methods used to separate @ wide varity of mixtures. The particular

method employed to separate any given mixture depends upon the nature of ts constituents. The

following are some ofthe methods in wide we

‘The Different Methods of Separating Mixtures

Describe the diferent methods of separating mixtures

1. Filtration

This metho is bes applicable in separation of components of mixtures called suspensions

[A mixture of chalk dust or lour with water an be separated by filtering the suspension. The

suspended particles gt trapped inthe filter paper. The trapped particles ae called the residue.

The waters called he flate

(SREEFESE EG) sssrension

fins final (Gereitee

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2. Decantation

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3. Evaporation

A mint of st or ugarin wate can be separated by aplying this method

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4. Simple distillation

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5. Fractional distillation

coun nfs back in the flask bees the temperate of te eum belo is baling

peta 10°C

The tenpertue onthe thmomeer says at 78°C ull he ethanol fas sil ovr

Evenly te themometeeding rises above 78. Ths i sg tat alte tana hasbeen

sept, being canbe stopped. By washing he temperate careful, the wo is

fiat so wich scan apr cn conden. Cs beds inthe ca vie a

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6. Sublimation

naphthalene. A mitre of anya thes ols with nother oid canbe sparatedby sublimation

wal ofthe iter famnl. The Sodium chloride islet in he beaker

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7. Chromatography

example ofthis isthe separation of yes that make up back ink. Chromatography wovks beter

ctromatography, namely column chromatography and paper chromatography. The two types of

veto

Observation

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Findings

The diferent colours of the ink make a pattern of colours formed during the process of

chromatography. This pattern of colours i called a chromatogram

Figure aboveshows a chromatogram of black ink. The blue ink has the fastest speed. This means

itis the most soluble in water and least absorbed by the paper. The geen ink has travelled lest

This means isthe leat soluble in water and most absorbed by the paper.

Paper chromatography showing the separated components of lack ink

Uses of Chromatography

Chromatography is used in many different ways. The following ae some of the application of

chromatography.

samples

8. Layer separation

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10. Centrifugation

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11. Magnetic separation

12. Crystallization

13. Winnowing or threshing

This is a method used to separate grains from husks or bran. The process makes use ofthe

differences in density ofthe constituents inthe mixture. When the winnower i shaken around

rain, being denser than husks or bra, snk othe bottom ofthe winnower

“The lest dene sh or bran moves othe top. They ee the Blown off the winsower by wind or

teeth, of sometime picked by hand and separated fom the grin.

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‘The Significance of Separating Different Mixtures

Explain the significance of separating diferent mires

‘We separate mites in ode wo obtein the mintre contents and pu hem ito appropeiie

use, The world around us is made up of mintres of diferent substances. These substances ae

often of lite use when they are inthe form of a mixture. Fr this reson, seperation of the

1. (9 Fractional distiation

erosene, diesel, Ibricating oils, wates, asphalt and bitumen. All thse factions have a

significant we in man’s industri, domestic and commercial actives. The factions or we of

all these factions is well koown to everyone of us. Can you mention the fiction of each

faction? You wil lam ore shou these prodect inorganic chemi section,

(ii) Fractional distillation of liquid air

Separates the air into its component gases. This is important because these components have

‘many uses in our everyday life. Some of these fractions and their functions are summarized

below

Component Use

Nitogen Manufacture ofetlizer

Oxygen Used in hospital, sel making, diving and space rave

Argon Filing light bulbs

Carbon dioxide Fre extinguishing, wed in carbonate drinks, te

etiam Filling ships and water balloons

Keypton and Xenon Used in photographic fash amps

2 Filtration and purification of drinking water make use of processes such as decantation,

filtration and sometimes distillation. The bottled water we drink is prepared by some or

‘combination ofthese processes.

3. In mining, an electromagnet is used to separate magnetic iron ore from other materials in the

crushed ore

4, In the manufacture of ethanol by fermentation in breweries, distillation is used in the final

stage to purify ethanol to its purest form (surgical spirit) in which the ethanol is usually sold

Likewise, distillation of fermented starch (8-12% ethanol), yields aleoholic drinks called spits

(whisky, gin, brandy, rum) which contain about 35-40% ethanol

5. (i) Paper chromatography is very useful in analysis of substances present in a solution. For

example, it can tell whether a substance has become contaminated or otherwise. This can be very

important, because contamination of food or drinking water, for instance, may be dangerous to

cour health,

Gi) Chromatography bas proved very useful inthe analysis of biologically important molecules

such as sugars, amino acids, and nucleotide bases. Molecules such as amino acids can be seen if

the paper is viewed under ultra-violet light

(Gi) Paper chromatography isthe test that can be used to check forthe purity of a substance, If

the sample is pure, it should only give one spot when run in several different solvents.

6, Other separation methods are also used to check whether purification has been successful

‘Samples obtained by distillation can be re-istilled. The purity of crystals can be improved by re-

crystallisation, A water sample can be tested for amount of dissolved material by evaporating @

certain amount of water to dryness. The solid waste can be weighed. This would give the amount

of dissolved solid in the water

“The process of purification is of crucial importance in many areas of chemical industry. Medical

drugs (pharmaceuticals) must be of highest possible degrees of purity. Any contaminating

substances even in very small amounts may have harmful side effects

7. (i) Separation of cream from whole milk is done by the process of centrifugation. As the milk

is spun, the heavier contents are forced down and the lighter cream rises up, After centrifugation,

the cream is poured off the top by decantation. This is the initial stage of milk constituent

separation, afer which other components such as milk proteins (cheese) are separated.

(i) Centrifugation is applicable in blood analysis, where the sold part of blood is separated from

the liquid part by centrifugation. Blood is a suspension containing microscopic blood cells

(corpuscles) ina liquid called plasma. If blood is centrifuged in a test tube, the blood cells are

‘lung tothe bottom, leaving the liquid plasma on top

8. Knowledge of separation of two immiscible liquids can be applied in the extraction of metals

such as iron from ther ores. For example, a the base of the blast furnace, the molten slug forms

1 separate layer on top of the liquid iron, The two can then be “tapped” off separately. The

‘method is very useful in organic chemistry as part of the process called solvent extraction,

9. Evaporation process is used in the extraction of common salt from seawater whereby the sun

‘evaporates water molecules ftom salty wate, leaving crystals ofthe salt behind,

100

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