Chemistry Lesson Notes
FIRST TERM E-LEARNING NOTE
SUBJECT: CHEMISTRY CLASS: SS1
SCHEME OF WORK
WEEK TOPIC
INTRODUCTION TO CHEMISTRY
LABORATORY FAMILIARIZATION
NATURE OF MATTER
ELEMENTS & SYMBOLS, VALENCY
COMPOUNDS AND MIXTURES
STANDARD SEPARATION TECHNIQUES FOR MIXTURES
PARTICULATE NATURE OF MATTER
IUPAC NOMENCLATURE OF CHEMICAL COMPOUNDS
ATOMIC NUMBER, MASS NUMBER, ISOTOPES AND CALCULATIONS
STRUCTURE OF THE ATOM: ORBITALS AND ELECTRONIC
STRUCTURE OF THE ATOM
REVISION
EXAMINATION
REFERENCE MATERIALS
New School Chemistry for Senior Secondary School by Osei Yaw A.
Practical Chemistry for Schools and Colleges by G. O. Ojokuku
Calculation in Chemistry by E.U. Akusoba and G.O Ewelukwa
WASSCE Past Questions and Answers on Chemistry
UTME Past Questions and Answers on Chemistry
WEEK ONE
TOPIC: INTRODUCTION TO CHEMISTRY
CONTENT
CHEMISTRY AS A SCIENCE SUBJECT
BRANCHES OF CHEMISTRY
SOME LABORATORY APPARATUSES AND THEIR USES
CHEMISTRY AS A SCIENCE SUBJECT
Science is an organized body of knowledge gathered through systematic experimentations and philosophical observations. Chemistry can be defined as a branch of science which deals with the study of the nature, structure, composition, properties and uses of all forms of matter and the changes in structure and composition which matter undergoes.
BRANCHES OF CHEMISTRY
Chemistry is divided into three main branches, namely
Physical chemistry
Organic chemistry
Inorganic chemistry
Physical chemistry deals with the physical aspect of chemistry like quantum theory, heat and electricity.
Organic chemistry deals with the study of carbon and its compounds.
Inorganic chemistry deals with the study of elements, their properties and uses
SCIENTIFIC METHODS OF DISCOVERIES
Scientific method of discovery includes the following steps and stages:
Observation
Pattern
Problem
Hypothesis,
Experiments
Theory
Law
Hypothesis refers to a prediction or guesses which explains an observed problem. When the hypothesis has been tested and found to be true within the limits of available evidence, it becomes a theory. A theory which has been extensively tested and proven correct without any exception becomes a scientific law.
EVALUATION
Define chemistry
State the stages or steps involved in scientific discoveries
When does a theory become a scientific law?
APPLICATIONS OF CHEMISTRY
Chemistry is applied in our everyday life as different activities take place in the environment. The effect of chemistry is felt in different aspects of life such as cooking, washing with soaps or detergent, digestion of food, drugs etc. Other applications of chemistry include health care, transportation, food, houses and clothes.
CAREER PROSPECTS IN CHEMISTRY
Chemistry is involved in our everyday lives and there is a vast range of careers open to those who have studied chemistry at any level. Great career opportunities exist both inside and outside the laboratory. You can choose a career from different fields such as:
Pharmaceutical/drug development
Science education
Chemical engineering
Mining and Metallurgy
Pure and applied chemistry
Petroleum and Petrochemical Engineering
Quality control
Medicine and surgery
Chemical analysis/forensic science
Environmental Chemistry
Science Laboratory Technology
Biochemistry etc
EVALUATION
State five applications of chemistry in our daily life.
Mention five adverse effects of chemicals and how they can be controlled.
GENERAL EVALUATION
Mention ten (10) career opportunities in chemistry.
List the branches of chemistry.
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio. Pg 2 to 7
Practical Chemistry for School and Collegs by G. O. Ojokuku pg 2-15
WEEKEND ASSIGNMENT
The aspect of chemistry that deals with the study of carbon and its compound is called (a) physical chemistry (b) Organic chemistry (c) Inorganic chemistry (d) Analytical chemistry
Which of the following is not an adverse effect of chemistry? (a) pollution (b) poisoning (c) emulsion (d) corrosion
A stage in scientific method of discoveries is (a) Evaporating (b) Hypothesis (c) Dehydrating (d) dissolving
A theory which has been extensively tested and proven correct without any exception becomes (a) scientific law (b) hypothesis (c) experiment (d) pattern
Career prospects in chemistry includes all the following EXCEPT (a) Biochemistry (b) Quality control (c) Accounting (d) Metallurgy
THEORY
State five applications of chemistry in our daily life
Mention five laboratory apparatus and their uses
WEEK TWO
TOPIC: LABORATORY FAMILIARIZATION
CONTENT
DEFINTION OF LABORATORY
LABORATORY APPARATUS; MEANING, USES AND IDENTIFICATION
LABORATORY SAFETY RULES
DEFINITION OF LABORATORY
A laboratory is a room or building equipped for scientific experimentation or research. It is a special facility where experiments are done and typically contains scientific equipment and apparatus.
LABORATORY APPARATUS
Laboratory apparatus refers to the various tools or equipment used by scientists working in the laboratory.
Some common laboratory apparatuses include: test tube, beaker, conical flask, flat bottomed flask, round-bottomed flask, funnel (plastic or glass) thistle funnel, brush, Woulff’s bottle tripod stand, retort stand, spatula, Bunsen burner, separating funnel, wire gauze, clamp, beehive shelf, gas jar, desiccated, reflux-condenser, Liebig condenser, pipette, burette, delivery tube, deflagrating spoon, u-tube, thermometer, aspirator bottle, wash bottle, chemical balance, reagent bottle, fume cupboard etc.
SOME LABORATORY APPARATUS AND THEIR USES
EVAPORATING DISH:
It is made of porcelain. It may be round or flat bottomed. It is used in the evaporation of solution to dryness
BEAKER: It is available in different sizes. It is flat bottom cylindrical, graduated and usually with a lip for easy pouring of solution. It is used to hold solution or measure solution during an experiment.
ASPIRATOR BOTTLE: It is a Jerry can made of plastic or glass with a screw tap. It is used for storing distilled water during an experiment.
CRUCIBLE: It is usually made of porcelain with a lid to match. It can withstand high temperature hence, it is used for ignition of substances until they are decomposed.
WOULFF’S BOTTLE: It is a glass bottle used during the preparation of dry gases to hold liquid or solutions that are employed as drying agents or in absorbing unwanted gases.
CONICAL FLASK: It is commonly used during titration experiments. It is usually graduated and used to estimate the volume of a solution.
FLAT AND ROUND BOTTOM FLASKS: They are made of glass and are mainly used for boiling especially during distillation experiments.
STANDARD VOLUMETRIC FLASK: It has a flat-bottom, pear-shaped and with a narrow neck. It is used in preparing standard solutions to a specific or definite volume.
FUME CUPBOARD: It is usually a wooden cupboard with its front made of glass which can easily move up and down. It is used to prepare poisonous gases
DISTILLATION FLASK: It has a flat or round bottom with a slanting long side arm. It is used during distillation.
BELL JAR: It is made of thick glass, cylindrical, tall and usually with a knob at the top. It is used in combustion experiments.
GAS JAR: It is made of thick glass, cylindrical, tall and sealed at the bottom. It is used for the collection of gas over water or dry gas
DROPPING BOTTLE OR DROPPING PIPETTE: It is used in keeping or transferring solutions or reagents that are required in drops during experiments.
SPATULA: It is made of iron which looks like a spoon. It is used in transferring little quantity of solids into test tubes
BURETTE: It is used during titration experiments and also in transferring small volume of solution.
RETORT STAND WITH CLAMP: It is used as support during experiments
DESSICATOR: It is used in keeping and drying solids in an atmosphere that is dry and free of dust.
MEASURING CYLINDER: It is used to measure the volume of solutions.
KIPPS APPARATUS: It is used in the intermittent supply of gases.
WIRE GUAZE: It is used as a support for flasks during heating.
FILTER FUNNEL: It is used in filling the burette or in supporting the filter paper during filtration.
CONDENSER (LIEBIG): It is used in cooling or condensing vapour into liquid during distillation or when refluxing.
CENTRIFUGE: It is used in separating fine solid particles in a liquid.
TEST-TUBE: It is used in qualitative analyses to hold reactants’
SEPARATING FUNNEL: It is used in the separation of immiscible liquids.
EVALUATION
Mention ten (10) laboratory pieces of apparatus you know and their uses
Define (a) Laboratory (b) Laboratory apparatus
IDENTIFICATION OF SOME LABORATORY APPARATUS
Identify the laboratory apparatuses and laboratory set-up labeled A-I below:
Dress well for the laboratory: Wear lab coat, safety goggles, footwear and tie long hair back to avoid catching fire
Keep pathways clear by placing items such as books and bags on the shelves or under the work table.
Do not taste or smell chemicals
Unauthorized experiments or procedures must not be attempted
Pay close attention to any cautions described in the laboratory exercise
Do not leave your assigned laboratory station without the permission of the teacher
Do not lean, hang over or sit on the laboratory tables
Fooling around or “horse play” in the laboratory is absolutely forbidden
Learn location of the fire extinguisher, eye wash station, first aid kit and safety shower.
Reports all accidents, injuries, and breakage of glass or equipment to instructor only.
Always follow the instructions given by your teachers
No eating or drinking in the laboratory at any time!
Leave your work station clean and in good order before leaving the laboratory
GENERAL EVALUATION
List ten safety measures in the laboratory
State the uses of: (a) Evaporating dish (b) Pipette (c) Retort stand (d) Measuring cylinder (e) Conical flask
READING ASSIGNMENT
Practical Chemistry for School and Collegs by G. O. Ojokuku pg 2-15
WEEKEND ASSIGNMENT
An apparatus in the laboratory in which the preparation of poisonous gases is done is called (a) distillation tank (b) Aspirator bottle (c) fume cupboard (d) bell jar
In the laboratory _______ is used for the collection of a gas over water (a) gas jar (b) Woulff’s bottle (c) reagent bottle (d)burette
Two liquids which are immiscible with each other can be separated using (a) bell jar (b) gas jar (c) wash bottle (d) separating funnel
An apparatus used to hold drying agents during the preparation of dry gases is (a) conical flask (b) gas jar (c) Woulff’s bottle (d) flat bottom flask
Coloured reagent bottles are used to store reagents which are capable of _____ easily by sunlight (a) evaporating (b) decomposing (c) dehydrating (d) dissolving
THEORY
a. Define Laboratory
b. List five safety measures that must be taken when in the laboratory
State the use of the following apparatuses
Separating funnel
Condenser
WEEK THREE
TOPIC: NATURE OF MATTER
CONTENT
NATURE OF MATTER
COMPARISON BETWEEN SOLID, LIQUID AND GAS
TYPES OF CHANGE
NATURE OF MATTER
Matter is anything that has weight and occupies space. It exists in three states namely: solid, liquid and gas.
The fundamental difference between the three states of matter depends on the degree of movement of the particles they are made of.
SOLID STATE
The particles of a solid are tightly packed and held together by a strong electrostatic force.
The particles only vibrate to and fro about an equilibrium or a fixed position. They have a definite shape and volume and very difficult to compress.
LIQUID STATE
The forces of attraction between molecules of liquids are weak compared to that of solids. Hence they have slight movements. This is why liquids can flow. They have definite volume but not definite shape.
GASEOUS STATE
As a result of the distance between the molecules of gases, the cohesive forces between them are very negligible and so they move randomly. Gases have no definite shape and volume. They assume the shape of the containing vessel.
EVALUATION
What is matter?
List and explain the three states of matter.
COMPARISON BETWEEN SOLID, LIQUID AND GAS
SOLID LIQUID GAS
1. Fixed mass Fixed mass Fixed mass
2. Very dense Less dense Least dense
3. Definite shape Shapeless Shapeless
4. Definite volume Definite volume No volume
5. Incompressible Incompressible Compressible
6. Particles vibrate Particles vibrate, Particles move
and move about rotate and move about constantly
a fixed position about a restricted space at a fixed speed.
EVALUATION
Define matter
Compare the three states of matter in terms of (a) density (b) compressibility
TYPES OF CHANGES
Whenever a given substance is heated, its state changes. There are two types of changes: physical and chemical.
PHYSICAL CHANGE:
A physical change is a change which is easily reversible and in which no new substances are formed. Examples are:
Dissolution of common salt
Changes in states of matter such as melting of solids, freezing of liquids, evaporation of liquids, liquefaction of gases to solids, sublimation of solids.
Magnetization and demagnetization of iron nails.
Separation of mixture by evaporation, distillation, fractional distillation etc.
EVALUATION
What is a physical change?
Give two examples of a physical change.
CHEMICAL CHANGE:
A chemical change is a change which is not easily reversible and in which new substances are formed.
Examples of chemical change
Rusting of iron/metals.
Dissolution of metals and limestone in acids.
Fermentation and decay of substances.
Changes in electrochemical cells.
The addition of water to quick lime.
Burning of materials.
COMPARISON BETWEEN PHYSICAL AND CHEMICAL CHANGES
Physical Change Chemical Change
1. Easy to reverse Difficult to reverse
2. No new substances are New substances are always
formed formed
3. Very little energy changes There are often large heat
take place change.
4. No change in mass The new substances formed have
different masses but the total mass is unchanged.
GENERAL EVALUATION/REVISION
What is a chemical change?
Give two examples of a chemical change.
State three differences between physical and chemical changes.
State the function of the following laboratory apparatuses: a) Fume cupboard b) Burette (c) Bunsen burner
READING ASSIGNMENT
New School Chemistry for SSS by O.Y. Ababio.Pg 8 -9
WEEKEND ASSIGNMENT
Which of the following changes is a chemical change? (a) melting of ice (b) liquefaction of air (c) slaking of lime (d) evaporation of a liquid
Which of the following substances will occupy a wider space? (a)carbon (iv) oxide (b) liquid milk (c) pieces of chalk (d) water
When a solid changes to gas directly, this process is called (a) freezing (b) sublimation
(c) vaporization (d) evaporation
Which of the following changes produces a new substance ?(a) reaction of water with sodium chloride (b) addition of acid to base (c) turning of margarine to oil (d) evaporation of water
Which one of the following has a fixed shape and volume?
(a) a cube of sugar (b) liquid wax (c) smoke (d) kerosene
THEORY
Give two differences between physical and chemical changes.
Give three processes, which involve a physical change
WEEK FOUR
TOPIC: ELEMENTS, SYMBOLS & VALENCY
CONTENT
ELEMENTS AND SYMBOLS
CLASSIFICATION OF ELEMENTS
VALENCY
ELEMENTS AND SYMBOLS
An element is a substance which cannot be split into simpler units by ordinary chemical process. There are over one hundred known elements.
SYMBOLS OF ELEMENTS
There are three ways in which symbols of elements are derived.
From the first letter of the name of the element
Element Symbols
Hydrogen H
Oxygen O
Iodine I
Fluorine F
Nitrogen N
Sulphur S
Carbon C
Phosphorus P
The first letter written in capital letter and one other letter from its name written in small letter.
Element Symbol
Chlorine Cl
Bramine Br
Calcium Ca
Aluminium Al
Magnesium Mg
Berylium Be
Helium He
Neon Ne
Lithium L
The symbols of some elements were derived from their Latin names.
Elements Latin name Symbols
Mercury Hydragyrium Hg
Sodium Natrium Na
Iron Ferrum Fe
Copper Cuprum Cu
Silver Argentum Ag
Tin Stannum Sn
Gold Aurum Au
Potassium Kalium K
Lead Plumbum Pb
EVALUATION
How many elements are discovered now?
Write the symbols for the following elements: silicon, iodine, fluorine, sulphur, silver, Iron, copper, potassium and sodium.
CLASSIFICATION OF ELEMENTS
Elements can be classified into metals and non-metals.
Examples of metals include iron, zinc, tin, aluminium, copper etc.
Examples of non-metals are: Chlorine, oxygen, sulphur, fluorine, hydrogen etc.
Some elements however possess the properties of metals as well as non-metals. They are called metalloids, examples are silicon and germanium.
THE DIFFERENCES BETWEEN METALS AND NON-METALS
Metal Non – metals
1. They are solids (except mercury) They are solids, liquids and gases
2. Good conductors of heat Poor conductors of heat and electricity
and electricity (except graphite which conduct electricity)
3. Malleable Brittle
4. Ductile Not ductile
5. Shiny Not shiny
Often very dense Usually less dense(low density)
(high density)
EVALUATION
What are metalloids?
State two differences between metals and non-metals.
VALENCY
Valency is the combining power of an element. It can also be defined as the number of hydrogen atoms that can combine with or replace one atom of that element.
Valency of an element depends on the structure of that element. At times it corresponds to the number of electrons in the outermost shells called valence electrons.
Below are the valencies of some elements:
Element Symbol Valency
Aluminium Al +3
Argon Ar Nil
Calcium Ca +2
Chlorine Cl -1
Sulphur S -2, -4 or -6
Sodium Na +1
Magnesium Mg +2
Copper Cu +1 or +2
Carbon C -2 or -4
Barium Ba +2
Silver Ag +1
Iron Fe +2 or +3
Valencies have either positive or negative values showing whether electrons are gained or lost. If an element gains electrons, its value is negative but positive when it loses electrons.
Generally, metals exhibit positive valencies while non – metal tend to have negative valencies. Some element exhibit more than one valency. Valency can also be called oxidation number or state.
RADICALS
A radical is a group of atoms having an electric charge either positive or negative which keeps its identity and react as a single unit. Any small group of atoms carrying a negative charge is called an acid radical. Examples of acid radicals include S042-, C032-, N03-
The valency of a radical corresponds to the charge it carries.
Radical Formula Valency
Ammonium NH4+ +1
Hydroxide 0H- -1
Trioxonitrate(V) N03- -1
Dioxonitrate(III) N02- -1
Trioxocarbonate(IV) C032- -2
Tetraoxosulphate(VI) S042- -2
Hydrogen trioxocarbonate HC03- -1
GENERAL EVALUATION/REVISION
Define (i) valency (ii) Radical
Write the valency of: a) Oxygen (b) Potassium c) Sulphur d) S042- e) NH4+
Classify the following into physical or chemical changes: a) Rusting of iron b) Fermentation of palm wine c) Evaporation of a salt solution d) Melting of ice
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio. Pg 26, 32-33
WEEKEND ASSIGNMENT
The combining power of oxygen is (a)+2 (b)-2 (c)-1 (d)+1
Which of the following is a metalloid? (a) sulphur (b) iron (c) silicon (d) carbon
The symbol Au represents (a) silver (b) lead (c) copper (d) gold
Which of the following elements is used as a standard in defining valency?
(a) oxygen (b) copper (c) carbon (d) hydrogen
Which of the following metals is a liquid at room temperature?
iron (b) gold (c) tin (d) mercury
THEORY
1. a. Define an element.
Write the symbols of the following elements
(i) Manganese (ii) Caesium (iii) Cobalt
2. a. What are metalloids?
Give two differences between metals and non-metal
WEEK FIVE
TOPIC: COMPOUNDS AND MIXTURES
CONTENT
COMPOUND
FORMULAE OF COMPOUNDS
MIXTURES
DIFFERENCES BETWEEN COMPOUNDS AND MIXTURES
COMPOUND
A Compound is a substance which contains two or more elements chemically combined together. A compound is formed as a result of chemical change.
Examples of compounds are
Compound Constituent Elements
Water Hydrogen, oxygen
Sand silicon, oxygen
Limestone calcium, carbon, oxygen
Common salt sodium, chlorine
Ethanol carbon, hydrogen, oxygen
PROPERTIES OF A COMPOUND
It has properties different from those of its component elements.
Its formation often requires large amount of heat.
It cannot be separated by physical means.
The components of a compound have a fixed ratio by mass.
Compounds are homogenous.
EVALUATION
Define a compound.
Give three examples of a compound.
FORMULAE OF COMPOUNDS
When an element exists as a molecule, a number is written as a subscript after the symbol of that element. For example, hydrogen is written as H2 and oxygen as 02.
A compound contains whole numbers of atoms of the component elements. Its molecular formula is written as follows.
The symbols of all the component elements are written close together as a group.
The number of atoms of each component element is written as a subscript after the symbol of that element.
Examples
Compound Formula
Hydrochloric acid HCl
Water H20
Ammonia NH3
Carbon(IV)oxide C02
Lead II chloride PbCl2
Calcium trioxonitrate(V) Ca(NO3)2
WRITING FORMULA FROM VALENCIES
Formulae of compounds can be deduced from the valencies of the component elements or radicals, following the rules below.
Write the symbols of the element or radicals in a compound
Write their valencies below the symbols of elements/radicals
Exchange their valencies.
Now write the formula of the compound bringing the symbols of the element or radicals together
Examples
Write the formula of sodium tetraoxosulphate(VI)
Rule 1 Na S04
Rule 2 & 3 1 2
Rule 4 Na2S04
Write the formula of calcium chloride
Rule 1 Ca Cl
Rule 2 & 3 2 1
Rule 4 CaCl2
EVALUATION
Write the formulae of; (i) tetraoxosulphate(vi) acid (ii) Magnesium Chloride
State three properties of a compound
MIXTURES
A mixture contains two or more constituents which can easily be separated by physical methods.
Examples of mixtures with their constituents are outlined below:
Mixture Constituents
Air Oxygen, Carbon (iv)oxide, nitrogen, rare gases, dust, moisture
Soil Sand, clay, humus, water, air, mineral salts
Urine urea, water, mineral salt
Palm wine water, sugar, alkanol, mineral salts, vitamins, yeast, protein, fat
Coca-cola water, sugar, cola, CO2
Milk water, sugar, fat, protein, mineral salts, vitamin
Sea water water, mineral salts, bacteria, remains of organic matter
Brass copper and zinc
DIFFERENCES BETWEEN MIXTURES AND COMPOUNDS
Mixture Compound
1. It may be homogenous It is always homogenous.
or heterogeneous.
2. It can be separated into It cannot be separated into its
its constituents by physical components by physical means.
means
3. The constituents can be The components are present in a
added in any ratio by mass fixed ratio by mass. Hence a
Hence a mixture cannot be compound can always be repre-
represented by a chemical sented by a chemical formula.
Formula.
4. The properties of a mixture The properties of a compound
are the sum of those of its are entirely different from those
individual constituents. of its components.
EVALUATION
List five (5) compounds and their formulae
What is a mixture?
State four differences between compound and mixture
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio. Pg 11, 36 to 37
GENERAL EVALUATION/REVISION
State the valency of the following elements and radicals: Na, K, S, O, SO42-, NO3-, CO32-
Write the formula of: a) Lead (ii) tetraoxosulphate (vi) b) Hydrochloric acid c) Sodium trioxocarbonate (iv) d) Calcium hydroxide
WEEKEND ASSIGNMENT
Which of the following is a mixture? (a) water(b) sugar(c) milk (d) starch
Which of the following is a compound? (a) water (b) soil (c) diamond (d) graphite
Which of these formulae represents ammonia? (a) NH3 (b) NH4+ (c) NH2 (d) CH4
The formula for sand is (a) C02 (b) SO2 (c) NO2 (d) SiO2
Compounds are always (a) heterogeneous (b) homogeneous (c) homogeneous or heterogeneous (d) chemogeneous
THEORY
1. a. Define (i) Compound (ii) Mixture
b. Give two examples each of compound and Mixtures
2. a. State four differences between compound and mixture
b. What is the formula of
i) tetraoxosulphate (vi) acid
ii) Ammonium sulphide
iii) Sodium tetraoxophosphate
WEEK SIX
TOPIC: STANDARD SEPARATION TECHNIQUES
CONTENT
STANDARD SEPARATION TECHNIQUES
STANDARD SEPARATION TECHNIQUES
The importance of separating a mixture into its constituents cannot be over emphasized since most substances are needed in their pure form. There are many standard separation techniques. Some of these separating techniques are filtration, centrifugation and decantation. Others include sieving, magnetic separation and sublimation, evaporation, crystallization, fractional precipitation, distillation, fractional distillation, using separating funnel and chromatography.
FILTRATION
Filtration is a separation technique that involves separating an insoluble solid from liquid using a filter. For example, a mixture of chalk particles in water can be separated using filtration technique. Filtration is used in industries such as water purification plants and breweries.
CENTRIFUGATION
A CENTRIFUGE MACHINE
Centrifugation is a standard separation technique used to separate a mixture of insoluble solid from liquid by using a centrifuge. A centrifuge is a machine which can spin test tubes containing suspensions at high speed. Centrifugation is often used when there is only a small amount of material. In hospitals, blood samples are centrifuged to separate the blood cells from the plasma.
DECANTATION
Decantation is a separation technique used to separate a mixture containing insoluble solid from a liquid. This is done when the mixture is allowed to settle down with the upper clear liquid carefully poured or decanted into a clean container thereby leaving the lower solid in the container originally containing the mixture. This is a quick but inaccurate method of separating the components of a mixture.
EVAPORATION
Evaporation is a separation technique used to recover soluble solute from its solvent. For example salt can be separated from salt solution by evaporation.
A Salt Evaporation Pond
Evaporation is used in salt –making industries.
CRYSTALLIZATION
Crystallization is used to obtain pure crystals of salts which decompose easily on heating from its solution. The solution is concentrated by heating. It is allowed to cool down and crystals start to form. To induce crystal formation:
add crystals of the salt (seedling)
scratch the inside of the container with a glass rod
Crystallization is used in industries where purity of the product is important, such as in drug industries and sugar industries.
FRACTIONAL CRYSTALLIZATION
It is used to separate two or more solutes (solids) which are present in the same solution. The solutes to be separated must have different solubilities at different temperatures. Starting from a particular temperature, as cooling of the solution of those solutes takes place, the crystals of the relevant solutes appear leaving the other solutes in the solution.
EVALUATION
Explain briefly the following methods of separation of mixtures: (a) Filtration (b) Decantation (c) Centrifugation
Explain how a pure sample of copper (II) tetraoxosulphate (VI) crystals can be obtained from its solution in the laboratory.
How would you separate a mixture of PbCl2 and NaCl
PRECIPITATION
In precipitation, a difference in the solubility of a solid in two different miscible liquids is used. For example, FeS04 is soluble in water but not on ethanol. If ethanol is added to a solution of FeS04 in water, the FeS04 will be precipitated out of the solution and filtered out.
SUBLIMATION
Sublimation is the change of state from solid to gas directly on application of heat. Examples of substances that sublime are iodine and ammonium chloride. Sublimation can be used to separate these substances. The pure crystal recovered is the sublimate.
DISTILLATION
This is used to recover a solvent from a solution. It involves vapourising a liquid and then condensing the vapour into a liquid called distillate. The solute and other impurities remain in the distillation flask. It is used in gin and water distilleries to manufacture gin and distilled water.
FRACTIONAL DISTILLATION
This is used to separate a mixture of two or more miscible liquids based on their boiling points. When two liquids have boiling points that are very close (less than 100oC the use of simple distillation becomes difficult. A fractionating column is inserted into the distillation flask. It is used to separate crude oil into fractions, separation of liquid air into oxygen and nitrogen, manufacture of spirits and to separate benzene and methyl benzene mixture.
EVALUATION
1. State the major difference between distillation and fractional distillation in terms of (a) Features of the apparatus (b) Mixtures to be separated
2. Explain the following separation techniques
Precipitation
Sublimation
SEPARATING FUNNEL
This is used to separate immiscible liquids. It depends on the densities of the two liquids. The less dense will be on top and the denser below. It is used to separate water and kerosene
SIEVING
This is used to separate solid particles of different sizes. Particles smaller than the size of the sieve (mesh) pass through leaving behind particles of larger sizes. It is used in gold and diamond mines and in garri industries.
MAGNETIC SEPARATION
This is used to separate magnetic substances from non-magnetic particles. It is used in mining and steel industries. It can be used to remove magnetic impurities from tin ores. It can be used to separate iron filings from sulphur powder.
CHROMATOGRAPHY
This method uses a solvent moving over an adsorbent medium (paper) which is porous to separate mixtures of solutes.
Types
Paper chromatography
Thin layer chromatography
Gas chromatography
Column chromatography
In paper chromatography, a solution, such as ink, is spotted into the paper near one end. The paper is dipped into an appropriate solvent such as water or ethanol in a closed air-tight jar. The solvent moves up the paper. The paper is removed and dried. The different spots on the paper show the different substances the solution (ink or dye) contains.
It is used in medicine to analyze blood. In industry, it is used to identify petroleum fractions. It is also used in scientific research.
CRITERIA FOR PURITY
The melting point and boiling point of a pure substance are fixed but change in the presence of impurities. Impurities lower the melting point of a substance and increase its boiling point
A pure substance gives one spot on a paper chromatogram.
GENERAL EVALUATION
Explain the following separation techniques. Magnetic separation, paper chromatography and sieving
Describe how you would separate a mixture of NaCl, PbCl2 and NH4Cl
What method can be applied to separate a mixture of iron filings and sulphur
Mention two criteria for purity of a substance.
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio.Pg 16 to 20
WEEKEND ASSIGNMENT
A mixture of oil and water can be separated by (a) sublimation (b) evaporation to dryness
(c) using a separating funnel (d) fractional distillation
Fractional distillation is used to separate (a) an insoluble substance from a soluble volatile substance (b) liquids with differing boiling points (c) gas, liquid or solid impurities from a mixture (d) liquid with close boiling points
Which of the following separating techniques can be used to separate a mixture of iodine and sodium chloride? (a) distillation (b) evaporation (c) sublimation (d) decantation
Which of the following is not a type of chromatography ?(a) thin layer (b) gas (c) paper
(d) glass
Which of the following is a quick but inaccurate way of separating mixture? (a) decantation (b) evaporation (c) filtration (d) distillation
THEORY
Explain briefly the following separation techniques (a) evaporation (b) filtration (c) fractional distillation
Mention two criteria for purity of a substance.
WEEK SEVEN
TOPIC: PARTICULATE NATURE OF MATTER
CONTENT
ATOMS AND MOLECULES
IONS
DALTON’S ATOMIC THEORY
MODIFICATIONS OF DALTONS ATOMIC THEORY
ATOMS AND MOLECULES
Matter is made up of discrete particles. The main ones are atoms, molecules, and ions.
An atom is the smallest part of an element which can take part in a chemical reaction.
A molecule is the smallest particle of a substance that can exist alone and still retains the chemical properties of that substance. Molecules are made up of atoms.
Atomicity of an element is the number of atoms in one molecule of the element.
We have monatomic, diatomic and triatomic for those elements that contain one atom, two atoms and three atoms respectively in their molecules.
Examples:
Element Atomicity
Hydrogen Diatomic
Oxygen Diatomic
Nitrogen Diatomic
Neon Monoatomic
Helium Monoatomic
Argon Monoatomic
EVALUATION
Define an atom.
Give two examples of diatomic molecules.
IONS
An ion is an atom or group of atoms which carries an electric charge. Such groups of atoms that carry either a positive or negative charge are called RADICALS.
An acid radical is thus a small group of atoms carrying a negative charge that keeps its identity. Examples include S042-, N03- e.t.c.
Generally ions are grouped as cations and anions. Cations are positively charged ions e.g Ca2+, Na+, NH4+ e.t.c.
Anions are negatively charged ions e.g.. C032-, S042-, Cl-, OH-, etc.
EVALUATION
What are ions?
State the cation and anion present in (I) H2S04 (ii) NaCl (iii) FeS04
DALTON’S ATOMIC THEORY
John Dalton, British Physicist and Chemist (1808) proposed the atomic theory thus:
All elements are made up of small indivisible particles called atoms.
Atoms can neither be created nor destroyed in any chemical reaction.
Atoms of the same elements are exactly alike in aspect and are different from atoms of all other elements.
Atoms of different elements can combine in simple whole number ratios to form compounds.
All chemical changes result from the combination or separation of atoms
MODIFICATIONS OF DALTON’S ATOMIC THEORY
Due to new discoveries in the twentieth century, Dalton’s atomic theory cannot hold in its entirety. There is need for its modification.
The first statement has been proved wrong by Rutherford’s discovery of protons, electron and neutrons as constituents of the atom. An atom is not an indivisible solid piece.
The second statement still holds good for ordinary chemical reactions. During nuclear reactions, however, the nucleus can be broken into simpler atoms giving out large amount of heat (nuclear fission). This destroys the atoms involved.
The discovery of isotopes makes the third statement unacceptable. Chlorine for example has two atoms with different nucleus content and hence different relative atomic masses although the same proton numbers.
The fourth statement is true only for inorganic compounds which contain a few atoms per molecule. Carbon forms very large organic molecules such as proteins, starch and fats which
contain thousands of atoms.
GENERAL EVALUATION/REVISION
State the modifications of the Dalton’s atomic theory.
A mixture contains propanone, ethanol and water with boiling point of 560C, 780C and 1000C respectively.
What method will be used to separate the liquids
Name the first liquid that will distil over. Explain your answer
Name an industrial process that uses fractional distillation
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio. Pg 25-26
WEEKEND ASSIGNMENT
Which of the following is not a constituent of the atom (a) proton (b) electron (c) neutron
(d) isotope
Which of the following statement about an atom is not correct? (a) it is indivisible (b) it is destructible in some cases (c) it is the smallest part of a substance that takes part in a reaction (d) it is made up of protons, neutrons and electrons
Which of the following is a liquid at room temperature? (a) copper (b) gold (c) mercury
(d) silver
How can you separate a mixture of iron filings and sulphur powder? (a) distillation
(b) chromatography (c) magnetization (d) evaporation
What is the atomicity of neon? (a) monoatomic (b) diatomic (c) triatomic (d) polyatomic
THEORY
Give any two postulates of the Dalton’s atomic theory.
(a) Differentiate an atom from a molecule.
(b) How will an atom become an ion?
WEEK EIGHT
IUPAC NOMENCLATURE OF CHEMICAL COMPOUNDS
CONTENT
Naming of:
---- binary compounds
---- radials and compounds having elements with variable oxidation numbers.
---- tertiary and quartenary compounds.
---- compounds with cations replaced with hydrogen.
NAMING OF BINARY COMPOUNDS
Nomenclature: This is the system of naming chemical compounds. The system is called IUPAC (International union of pure and applied chemistry). The naming is determined by the constituent elements in the compound and the oxidation number if necessary.
In naming binary compounds (compounds with only two elements), electropositive elements (cations) are usually named first while the electronegative elements (anions) come last with a modification of the name end with – ide.
Examples:
Formula IUPAC name
MgO Magnesium oxide
H2S Hydrogen sulphide
NH4Cl Ammonium chloride
NaH Sodium hydride
But in cases where the two elements involved are non-metals, the above rule is not followed. For example, H2O (water) NH3 (ammonia) and PH3 (phosphine)
EVALUATION
Name the following compounds: (a) NaCl (b) CaO (c) H2O2.
NAMING OF RADICALS AND COMPOUNDS HAVING ELEMENTS WITH VARIABLE OXIDATION NUMERS
Radicals (group of atoms of element carrying electrical charge) are treated as a single element when naming their compounds.
Examples of radicals with their names are as follows:
Radical IUPAC NAME
NH4+ Ammonium ion
OH Hydroxyl ion
But in naming acid radicals, the oxidation number of elements is indicated by Roman numbers in bracket.
Example:
Formula IUPAC
NO2 Dioxonitratei(iii) ion
NO3- Trioxonitrate(v) ion
CO32- Trioxocarbonate(iv) ion.
Also the compounds having elements with Roman numbers in bracket indicating their oxidation numbers in that compound
Examples
Formula IUPAC
FeO Iron (ii) oxide
Cu2O Copper (i) oxide
MgCO3 Magnesium trioxocarbonate (iv)
EVALUATION
Name the following compounds (a) Fe2O3 (b) CuO
What are the oxidation numbers of Fe and Cu in (1) above?
NAMING TERTIARY COMPOUNDS AND QUARTENARY COMPOUNDS.
These are compounds containing more than two elements.
Examples are oxo-acids, normal salts, and acid salts.
Acid IUPAC
HNO3 Trioxonitrate(v) acid
H2SO4 Tetraoxosulphate (vi) acid
H3PO4 Tetraoxophospate (v) acid
Examples of Normal Salts.
Normal salts IUPAC
KNO3 Potassium trioxonitrate (iv)
NaSO4 Sodiumtetraoxosulphate (vi)
CuCO3 Copper (ii) trioxocarbonate (iv)
EVALUATION
Determine the oxidation number of: a) C in H2CO3 b) Mn in KMnO4 c) Cu in CuSO4
Name the compounds in 1 above
NAMING OF COMPOUNDS WHOSE CATIONS HAS BEEN PARTIALLY REPLACED WITH HYDROGEN IONS.
In naming compounds whose cations have been partially replaced with hydrogen ion, the cations is named first followed by hydrogen, then the radicals present indicating the roman number standing for the oxidation number of the element that is combined with oxygen to form the radical.
E.g Formula IUPAC
NaHSO4 Sodium hydrogen tetraoxosulphate (vi)
KHSO3 Potassium hydrogen trioxosulphate (iv)
GENERAL EVALUATION/REVISION:
Determine the following oxidation number of a) C in LiHCO3 b) S in KHSO4 and name the compounds
Write the chemical formula of the following compounds a) Oxochlorate (I) acid b) Iron (ii) tetraoxosulphate (VI) pentahydrate
State the uses of the following laboratory apparatuses a) Condenser b) Kipp’s apparatus c)Tripod stand
READING ASSIGNMENT
Practical Chemistry for Senior Secondary Schools By Godwin O. Ojokuku pg 20-28.
WEEKEND ASSIGNMENT
The compound Na2S is called ____ (a) Sodium (ii) sulphate (b) Sodium sulphur (c) Sodium sulphide (d) Sodium sulphite.
The formula of sulphur (iv) oxide is (a) SO4 (b) SO2 (c) S2O4 (d) S4O2
Ammonium chloride can be written as (a) NH4Cl (b) NH3Cl2 (c) NH4HCl
(d) NH4OH
The IUPAC name of NaHSO4 is (a) Sodium bicarbonate (b) Sodium tetraoxosulphate (vi) acid (c) Sodium sulphate (c) Sodium hydrogen tetraoxosulphate (vi)
Which of the following compounds have cation with variable oxidation state.
(a) FeO3 (b) ZnCO3 (c) CuO (d) KU
THEORY
Name the following compounds (a) Fe2O3 (b) KMnO4 (c) KClO3
Calculate the oxidation number of (a) Sulphur in H2SO4 (b) Carbon in CuCO3
WEEK NINE
ATOMIC NUMBER, RELATIVE ATOMIC MASSES, ISOTOPES AND CALCULATIONS
CONTENT
ATOMIC NUMBER AND MASS NUMBER
ISOTOPES
CALCULATIONS OF RELATIVE ATOMIC MASS
CONSTITUENTS OF AN ATOM
Atoms are made up of sub-particles. Protons, electrons and neutrons. Proton has a positive charge, electron has a negative charge and neutron has no charge.
Atomic number and mass number
The atomic number of an element is the number of protons in the nucleus of its atom.
Mass number or atomic mass of an element is the sum of the number of protons and neutrons in the nucleus of its atom.
Mass Number = Number of proton + Number of neutron
An element X can be represented as
ZXA
where A= Atomic mass or mass number
Z= Atomic number
e.g. 40 mass no = 40
Ca
atomic no = 20
EVALUATION
State the constituents of an atom.
What is the number of proton in the following elements?
(a) 11B (b) 12C
6
ISOTOPES
Isotopy is the occurrence of atoms of elements having the same atomic number but different mass numbers. This is due to the difference in the number of neutrons present in the atoms. The atoms that exhibit isotopy are called ISOTOPES.
Examples of atoms that exhibit isotopy are chlorine 35Cl and 37 Cl
Carbon- 12 C, 13 C and 14 C
Potassium – 39K19 and 41K19
Oxygen - 16O16 and 18O16
EVALUATION
Define isotopy.
Write the isotopes of chlorine.
CALCULATION OF RELATIVE ATOMIC MASS
The following is an example of calculation of relative atomic mass of an element from percentage abundance of its isotopes.
1. X is an element which exists as an isotopic mixture containing 90% of 39X19 and 10% of 41X19
How many neutrons are present in the isotope 41X
Calculate the mean relative atomic mass of X
Solution
Neutrons in 41X19
= 41-19 = 22
b. R.A.M = 90 x 39 + 10 x 41
100
= 90 x 39 + 41 x 10
100
= 3920 = 39.20
100
EVALUATION
How many neutrons are present in the isotope 37Cl17 ?
A given quantity of chlorine contains 75% 35Cl17, and 25% 37Cl17, determine the relative atomic mass of chlorine.
CALCULATIONS
The following are more examples of calculations of relative atomic masses of elements.
An element Y exist in two isotopic forms 39Y18 and 40Y18 in the ratio 3:2 respectively. What is the relative atomic mass of the element?
SOLUTION
R.A.M of Y = 3 x 39 + 2 x 40
5 1 5 1
= 0.6 x 39 + 0.4 x 40
= 23.4 + 16
= 39.4
An element with relative atomic mass 16.2 contains two isotopes 16P8 with relative abundance 90% and mP8 with relative abundance 10%. What is the value of m?
SOLUTION
16.2 = 90 x 16 + 10 x m
100
16.2 = 9 x 16 + m
10 10
16.2 = 144 + m
10 10
16.2 = 144 + m
10
16.2 x 10 = 144 + m
162 = 144 + m
162 – 144 = m
18 = m
The value of m is 18
GENERAL EVALUATION/REVISION
Consider the atoms represented below:
qX rX
p p
State the relationship between the two atoms.
What is the difference between them?
Give two examples of other elements which exhibit the phenomenon illustrated.
State the number of electrons, protons and neutrons present in the following atoms/ions
Ca b) S2- c) Al3+ d) P
If an element R has isotopes 60% 12R6 and 40% xR6 and the relative atomic mass of R is 12.4, find x.
READING ASSIGNMENT
New School Chemistry for SSS by O.Y Ababio. Pg 48-49
WEEKEND ASSIGNMENT
The atomic number of an element is precisely
(a) the number of protons in the atom (b) the number of electrons in the atom (c) the number of neutrons in the atom
An atom can be defined more accurately as (a) the smallest indivisible parts of an element that can take part in a chemical reaction (b) the smallest part of an element that can take part in a chemical reaction (c) a combination of protons, neutrons
The mass number is (a) proton number + neutron number (b) electron number + proton number (c) neutron number + electron number
Calculate the relative atomic mass of an element having two isotopes 107 Ag and 109Ag in the ratio 1:1 (a)106 (b)107 (c)108
An element X has two isotopes 18.8X and 15.8X in the proportion of 1:9 respectively. Find the relative atomic mass of X (a)16.1 (b)13.6 (c)16.8
THEORY
1. (a) Define the term isotopy.
(b) Determine the number of electrons, protons and neutrons in each of the following: 39K19, 63.5Cu29
2. If an element R has isotopes 60% of 12R6 and 40% xR6 and the relative atomic mass is 12.4, find x.
WEEK TEN
TOPIC: STRUCTURE OF THE ATOM
CONTENT
Orbitals of The Atom
Electronic Structure Of the Atom
Filling Of Electrons in to Orbitals
Quantum Numbers
ORBITALS OF THE ATOM
The region in space within which there is maximum possibility of finding an electron in an atom is called an ATOMIC ORBITAL. We have s, p, d, and f orbitals.
Shapes of s and p orbitals are as follows:
s-orbital
px orbital
py orbital pz orbital
EVALUATION
Define atomic orbital
State the shape of (i) S-orbital (ii) P-orbital.
ELECTRONIC STRUCTURE OF THE ATOM
With the knowledge of atomic orbital the spectra of more complex atoms than hydrogen atom can be explained as follows:
a) that within a given principal quantum number or energy level, there are sub energy levels, i.e. energy levels otherwise called K,L,M,N,O,P AND Q shells have sub-energy levels otherwise called s,p,d and f orbitals
(b) The total number of sub-shells within a shell is given by n2
while the total maximum number of electrons is given by 2n2 where n is the number of enregy level.
Energy Level Number of orbitals Maximum No of electrons
n = 1(K- shell) 12 =1 2×12 =2
n =2 (L- shell) 22 = 4 2×22 = 8
n = 3 (M- shell) 32 = 9 2×32 = 18
n = 4 (N- shell) 42 =16 2× 42 = 32
n = 5 (O- shell) 52 = 25 2× 52 =50
n = 6 (P-shell) 62 = 36 2×62 =72
n = 7 (Q - shell) 72 = 49 2×72 = 98
(c) In a given orbital there could be a maximum of only two electrons and electron in all orbitals of the same type within a principal quantum number possess equal energies.
(d) The electrons in the different sub- shells or orbitals within a principal quantum number do not all have equal energies.
The gradation of energies of orbitals is as follows:
1s< 2s<2p<3s<3p<3d<4s<4p<4d---
EVALUATION
State the first five energy levels.
Calculate the total no of electrons when n is equal to (i) 2 (ii) 4.
FILLING OF ELECTRONS IN ORBITALS
In filling electrons into the atoms of elements, considerations are given to the conditions laid down by Aufbau Principle, Pauli exclusion principle and Hund’s rule of maximum multiplicity.
AUFBAU PRINCIPLE states that electrons go in to fill orbitals of lower energy first before filling orbitals of higher energy and each orbital may hold up to two electrons.
PAULI EXCLUSION PRINCIPLE states that no two electrons have identical sets of the four quantum numbers {n, l, m and s in an atom}.
HUND’S RULE OF MAXIMUM MULTIPLICITY state that in filling degenerate orbitals with electrons, electrons go in singly first before pairing up occurs.
EVALUATION
State the following principle
{a} Aufbau Principle {b} Hund’s rule.
QUANTUM NUMBERS
Studies show that the energy of an electron may be characterized by four quantum numbers. These are
{1}The principal quantum number represented by n with integral values of 1,2,3,4 e.t.c.
{2}The subsidiary or Azimuthal quantum number represented by l with integral values
ranging from O to (n-1).
(3) The magnetic quantum number represented by m with integral values ranging
from –l to +l.
4. The spin quantum number represented by s with integral values – 1/2 and = 1/2.
Element Atomic Number Electronic configuration.
H 1 1S1
He 2 1S2
Li 3 1S2 2S1
Be 4 1S2 2S2
B 5 1S2 2S2 2P1
C 6 1S2 2S2 2P2
N 7 1S2 2S2 2P3
O 8 1S2 2S2 2P4
F 9 1S2 2S2 2P5
Ne 10 1S2 2S2 2P6
Na 11 1S2 2S2 2P6 3S1
Mg 12 1S2 2S2 2P6 3S2
Al 13 1S2 2S2 2P6 3S2 3P1
Si 14 1S2 2S2 2P6 3S2 3P2
P 15 1S2 2S2 2P63S233P3
S 16 1S2 2S2 2P63S2 3P4
Cl 17 1S2 2S2 2P6 3S2 3P5
Ar 18 1S2 2S2 2P6 3S23P6
K 19 1S2 2S2 2P6 3S23P6 4S1
Ca 20 1S2 2S2 2P6 3S23P6 4S2
GENERAL EVALUATION
State the four quantum numbers.
Write the electronic configuration of the following a) Mg b) S2- c) Ca2+ d) Si
READING ASSIGNMENT
New School Chemistry By O.Y. Ababio pg 49-54.
WEEKEND ASSIGNMENT
1. Which of the following orbitals is spherical in shape?
s (b) p (c) d (d) f
2. Which of the following shells have a maximum of eight electrons ?
k (b) l (c) m (d) n
3. 1s2 2s2 2p6 3p1 is the electronic configuration of
potassium (b) calcium (c) sodium (d) aluminum.
4. “No two electrons have identical sets of four quantum numbers”. This statement is
Aufbau principle (b) Pauli exclusion (c) Hund’s rule (d) Rutherford’s model.
5. Which of the quantum number is represented by L?
principal quantum no (b) subsidiary quantum no (c) magnetic quantum
(d) spin quantum.
THEORY
State the following principle (a) Pauli exclusion principle. (b) Aufbau principle.
Write the electronic configuration of
(a) Oxygen
(b) Calcium (c) Chloride ion (Cl-) (d) Aluminum ion (Al3+)
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