CHEMISTRY FORM 1 Lesson Notes 2013 By Onyango

CHEMISTRY FORM 1 Lesson Notes 2013 By Onyango. Ngoye

Table of contents 1. Unit 1 Introduction to Chemistry 2. Unit 2 Simple classifications of substances 3. Unit 3 Acids, ashes and indicators 4. Unit 4 Air and combustion 5. Unit 5

UNIT ONE Introduction to chemistry Specific objectives. • Explain what the study of chemistry is. • Name and state the uses of common apparatus in the laboratory. • Describe a Bunsen burner and its flames. • State laboratory safety rules.

TOPIC SUMMARY a)Definition of chemistry. • Chemistry is a branch of science that deals with structures and composition of substances and the way they behave under different conditions. • Chemistry is studied by carrying out experiments to make some observations and drawing conclusions from the data collected.

b)Importance of studying chemistry The study of chemistry enables one to: • Discover new materials and new chemicals techniques applied in industrial processes. • Understand manipulate the environmental a factors affecting man. • Have knowledge in extraction of chemicals from plants and purification of substances. • It is a career subject.

c)Some chemistry concepts learnt in primary school level. Matter • Matter is anything that has mass and can occupy space. • The states of matter are: • Solids • Liquids • Gases

Conductors and Non-conductors • A conductor is a solid substance that allows electric current to pass through it. • Conductors are not decomposed by electric current. • All metals are conductors. Graphite is also a conductor. • Non-conductors are solid substances that do not allow electric current to pass through them. All non-metals except graphite are nonconductors

Drugs and drug-abuse • A drug is any natural or man made substance which when taken changes in some way the normal working of a body. • Drug-abuse is the use of drugs for any other purpose other than for which it is intended to. Over-the-counter drugs (OTC drugs) • These are medicinal drugs that can be bought from a chemist or a retail shop without doctors prescription. • Examples are painkillers and anti acids.

Drugs of Dependency Drugs of dependency These are drugs that contain substances that causes addiction and makes the user uncomfortable when they have not used them. How to prevent drug abuse. • Follow prescription and medicine dosage when using a medicinal drug. • Avoid taking any illegal drug. • Avoid the company of those who abuse drugs. • Utilize the leisure time properly.

Common Apparatus In A Laboratory. -A laboratory is a room equipped with chemicals and apparatus in which chemistry is studied. -Apparatus are pieces of equipments used to study chemistry. Apparatus could be made up of glass, plastic or metal. -Most apparatus are made up of glass because glass is transparent and does not react with most chemicals. -Apparatus can be classified according to their uses. Examples are;

§Apparatus for measuring volumes of liquids Graduated beakers Measuring cylinder Conical flask Volumetric flask Burette Apparatus in which substances are heated Test tubes Boiling tubes (are larger and wider than test tubes and gives room for sparting substances) Deflagrating spoon Round bottomed flask Crucible

Apparatus for measuring mass. • Beam balance • Electrical balance. Apparatus for measuring time. • Stop watch • Clock The Bunsen Burner • Diagram

Functions of the difference parts of a Bunsen burner • Chimney -Allows gases to mix. When gases are ignited they burn at the end of the chimney • Collar Regulates the amount of air entering into the chimney • Air hole -Allows air to enter into the chimney • Jet -Allows laboratory gas into the chimney. • Rubber -Connects the gas inlet to an external tubing source of laboratory gases. • Base -Supports the burner.

Types of flames of Bunsen burner - The type of flames produced when a Bunsen burner is lit depends on if the air hole is opened or closed. -They type of the flame produced when the air hole is closed is called a luminous flame. -The type of the flame produced when the air hole is opened completely is called a non-luminous flame.

Differences between luminous and non-luminous flames. LUMINOUS NON-LUMINOUS Formed when the air hole is closed Formed when the air hole is opened Produces a lot of light Produces a lot Large and wavy Small and steady Produce soot Does not produce soot Burns quietly Burns with a roaring sound

POINTS TO NOTE -When hot in use a lit Bunsen burner should be turned into a luminous flame because it is noticeable and does not ‘strike back’. -Non-luminous flame is preferred for heating substances in a laboratory because of its hot and does not produce soot which make apparatus dirty. -The almost colorless region of a non-luminous flame is cold and consists of unborn gases

Laboratory safety rules -When observed, safety rules prevent a chemist from the common laboratory accidents; burns, cuts, explosives, fire outbreak and eye damage. The following are the safety rules; -Enter the laboratory in an orderly manner. -Never run while in a laboratory. -Do not taste or eat anything in a laboratory. -Put off flames not in use. -Always consult your teacher before trying any new experiment. -Label the chemicals you are using to avoid confusion.

-Put away flammable substances away from flames. Always use a clean bench when carrying our experiments. -Always use a clean spatula to scoop chemicals from containers. -Always hold test tubes with a test tube holder when heating substances. -When heating substances, never point the open end of the tube towards yourself or anyone else. -Experiment in which poisonous gases are produced should be carried out in a fume chamber or in the open. -In case a chemical pours on your skin, rinse it with a lot of running water. -

Laboratory Rules Continued. • Never look directly into flasks where reaction is taking place. -Never smell gases produced during experiment directly instead direct the fumes carefully towards you, using your hand. -In case of an accident, a student should report the matter to the person in charge for first aid. Other students should remain cal, for panicking may worsen the situation. -Always dispose chemicals already used safely. -Always clean the bench and apparatus after an experiment. -Returns the apparatus into their correct place after use. -Wash your hands with running water before leaving the laboratory.

Topic Summary a)Mixtures • A mixture consists of two or more substances put together and can be separated by physical means. • The substance in a mixture are not chemically combined. • Substances in a mixture retain their physical and their chemical properties. b)Types of mixtures • There are 3 types of mixtures; • Solid/ solid mixtures e. g. sand iron filings. • Liquid/ liquid mixtures e. g. water and ethanol or water and kerosene. • Solid/ liquid mixtures e. g. salt and water or sand water.

c)Separating Mixtures. To separate an insoluble solid from a liquid e. g. sand from water. • There are two techniques: i)Decantation- the solid particles are allowed to settle and the liquids is poured off carefully. • Limitation – some solid particles may drop off with the liquid that is poured off.

ii)Filtration- the mixture is poured into a filter funnel fitted with a filter paper. Application of the separation techniques • Extraction of salt from seas and salty lakes e. g. L. Magadi. • Extraction of sugar from sugarcane.

• Extraction of medicinal substances from plants. ii)To separate two immiscible liquids e. g. water and kerosene. • Liquids are solids to be immiscible if they form layers when put together • Separating techniques • Use of separating funnel • Use of a teat pipette • Diagram on use of a separating funnel.

iii)To separate miscible liquids e. g. water and ethanol. • Two liquids are said to be miscible if they form a uniform mixture, when put together. • Separating technique • Fractional distillation • Conditions • Liquids must have close but different boiling points.

Application • To separate components of crude oil at Changamwe Oil Refinery. • Large scale isolation of oxygen and nitrogen from air. • Manufacturing of spirits. iv)To obtain a solute from a solution e. g. salt from water • A solute is a solid substance that dissolve in a liquid. • Solvent is a liquid substance in which a solute dissolves. • A mixture of a solute and a solvent is called a solution. • Technique • Evaporation- the mixture is heated to dryness

Application v)To obtain both solute and solvent from a solution e. g. to obtain salt and water from a salt solution. • Technique • Simple distillation

• To obtain pure water from areas where the available water is salty. vi)Separating coloured substances e. g. components of black ink. • Technique • Paper chromatography

Points to Note. • Chromatograms are the rings formed as the coloured substances separate. • A suitable solvent (such as propane) is introduced into the original spot of the dye for the colours to separate. • A solvent front is the farthest distance moved by a solvent on a chromatographic paper. • The ring formed near the solvent front is of the colour that is more soluble. • The ring formed near the original spot as of the colour that is less soluble.

vii)To extract oil from grains e. . g elianto pil from maize seeds. Techniques • Solvent extraction Procedure • Gride the seeds as you add a suitable solvent e. g. propane • Continue griding until an extract is formed • Filter the extract and pt the fitrate under the sun for propane to evaporate. • Confirm the liquid left as oil using a paper oil makes a paper to be translucent.

viii)Other separating techniques • Use of magnet • Hand picking • Sublimation d) Pure substances • A substance is pure if it does not contain other substances (impurities) in it. • The purity of a substance is determined by melting point or boiling point. • Impurities rises the boiling point of a substances and lowers the melting point of a substance.

e) Difference between permanent and non-permanent changes PERMANENT CHANGE NON-PERMANENT CHANGE i) A new substance is formed i) No new substance is formed ii) Mass of the substance changes ii) Mass of the substance iii) Change is not reversible iii) Change is reversible iv) Accomplished by heat changes iv)Not accompanied by heat

• A pure substance has a definite boiling point and a melting point. • Impure substances boil and melt over a range of values. • A boiling point is a specific constant temperature for particular liquid in which a liquid changes into vapour form. • A melting point is a specific constant temperature for particular solid in which a solid changes into a liquid form.

THE ATOMIC THEORY • An element is a substance which cannot be split into any simpler substances by chemical means. • An atom is the smallest particle of an element that possibly take part in a chemical reaction. • A compound is a substances formed when two or more elements react. • A molecule is the smallest unit of a compound.

Names of Some Elements &Symbols ELEMENT SYMBOL Carbon C Nitrogen N Sulphur S Hydrogen H Oxygen O iodine J

Examples of elements whose symbols are derived from English names and consists of two letters. ELEMENT SYMBOL Calcium Ca Chlorine Cl Zinc Zn Aluminium Al Bromine Br Magnesium Mg Manganese Mn helium He Argon Ar

iii)Examples of elements whose symbols are derived from their latin names. Elements Latin name Symbol Sodium Natrium Na lead Publum Pb copper cuprum Cu Silver argentum Ag Potassium kallium K Iron Ferrum Fe

Points to Note • When a symbol is represented using a single letter it should be a capital letter. • When a symbol is represented using two letter the first should be a capital letter while the second is a mall letter. The letters should not be joined.

UNIT THREE ACIDS, BASES AND INDICATORS

Specific Objectives • Prepare and use plant extract as acid-base indicators. • Use indicators to identify acids and bases. • State effects of acids on substances. What is an Acid? • An acid is a compound containing hydrogen ions which can be replaced either directly or indirectly by a metal or an ammonium ion (cationic radical). There are two types of acids

Organic acid and mineral acids. Examples Name of acid Where found - Citric acid -Lemon juice -tartaric acid -Baking powder, grapes and tamarids -carbonic acid -fizzy drinks -ethnoic acid -vinegar -tannic acid -tea

Common Mineral Acids Acid Chemical formula - Hydrochloric acid HCl -sulphuric acid H 2 SO 4 -nitric acid HNO 3 -carbonic acid H 2 CO 3

Properties of Acids Has a sour taste. Turns blue litmus paper to red. Have a p. H less than 7. Reacts with metals to form salt and hydrogen gas. Reacts with bases to form salt and water only. Reacts with metal carbonates to form salt, water and carbon (iv) oxide. • Reacts with metal hydrogen carbonates to form salt water and carbon (iv) oxide. • • •

Bases • Bases are substances which can neutralize an acid to give salt and water. • Soluble bases are called alkalis.

Examples of Bases BASE CHEMICAL FORMULA Sodium hydroxide Na. OH Potassium hydroxide k. OH Magnesium hydroxide Mg(OH)2 Calcium hydroxide Ca(OH)2 Sodium Oxide Na 2 O Potassium Oxide k 2 O

Important points to Note • Metal oxides and metal hydroxides are bases. • Sodium and potassium oxides and hydroxides a soluble bases (alkalis) • Properties of bases • Turn red litmus papers to blue • Neutralizes acids to form salt and water only. • Have p. H value of above 7.

Indicators • An indicator is a substance which changes to a certain colour in base and into a different colour in an acid. • To prepare an acid-base indicator from plant extract e. g. from flower petals.

Procedure of preparing Indicators from flower Extracts • Put flower petals into a mortar • Add a few drops of ethanol (suitable solvent) into flower petals • Crush the petals with a pestle as you add ethanol. • Warm the extract • Decant/filter the extract into a petri dish for ethanol to evaporate • The residue is the acid-base indicators. • Commercial indicators

Commercial indicators Indicators Colour in acid Colour in base - Litmus paper - Red - Blue -Methyl orange -Red(pink) -(yellow -Phenolphthalein -colorless -pink -screen Methyl orange -red/pink -yellow

Important points to Note • A universal indicator gives a Same of colours depending on the strength of an acid or a base • PH 7 - neutral solutions • PH less than 7 - bases • Colour of the universal indicator in a: • Strong acid- red • Strong base- violet • Weak acid- yellow • Weak base- blue

UNIT FOUR AIR AND COMBUSTION

Specific Objectives • State the percentage composition of air by volume • Carry out simple experiments to show that oxygen is the active part of air. • Determine the percentage of oxygen in air using suitable methods. • Describe the combustion of specified elements in air and oxygen and name the • products. • Explain how liquefied air can be separated into its components by fractional • distillation • Carry out experiments to investigate the conditions. Necessary for rusting and • state the composition of rust. State methods of preventing rusting • Prepare oxygen, investigate its properties and state its uses. • Arrange some elements in order of their reactivity with oxygen using • experimental data. State the uses of reactivity series.

Percentage Composition of Air by Volume Gas Percentage composition by volume - Nitrogen 78% -oxygen 215 -carbon(iv)oxide 0. 03% -noble gases 0. 97% -water vapour Variable -dust particles and other impurities Variable

Experimental Results • Mass of crucible + lid =xg • Mass of crucible + lid + Magnesium ribbon and before heating = yg • Mass of magnesium ribbon = X-Y =zg • Mass of crucible + lid + magnesium after the experiment =Ag • Mass of Magnesium Compound after experiment = A-Y +Bg • Percentage composition of oxygen

Important points to Note The mass of crucible contents after experiment is greater than that of its contents at the beginning of the experiment because oxygen is added to magnesium in heating magnesium ribbon • Combustion of specifies elements in air and oxygen • When a substance burns in air, oxygen is added (oxidation) and the mass increases.

Examples of Oxides formed under different Conditions. 2 C(s) + O 2(g) 2 CO(g) (limited) (carbon (II) Oxide) C(s) + O 2 (g) CO(g) (excess) (Carbon (IV) Oxide) 4 Na(s) + O 2(g) 2 Na 2 O(s) (cold) (sodium Oxide) 2 Na(s) +O 2(g) Na 2 O(s) (hot) (Sodium Peroxide) 4 P(s) + 3 O 2(g) 2 P 2 O 3 (limited) (Phosphorus (III) Oxide) 4 P(s) + 5 O 2(g) 2 P 2 Os (excess) (Phosphorous (V) Oxide)

Laboratory Preparation of Oxygen

Equation for the reaction 2 H 2 O 2 (l) manganese (IV) Oxide. O 2 (g) + 2 H 2 O(l) (Catalyst) Sodium peroxide and water could be used in place of hydrogen peroxide and Manganese oxide as in the equation. 2 Na 2 O 2 (s) O 2(g) + 2 Na 2 O (s)

Industrial preparation of oxygen by fractional distillation of liquid air. Air is a mixture of gases: - Carbon (IV) oxide (CO 2), water vapour (H 2 O), Noble Gases. Helium and argon, Oxygen (O 2) and nitrogen (N 2)

The reactivity Series • • • K Most reactive Na Ca Mg Al Zn Fe Pb Cu Hg Ag Au Least reactive

Redox iv)Competition for combined oxygen Oxidation- addition of oxygen to a substance Reduction- removal of oxygen from a compound In a redox reaction, a more reactive metal removes the combined oxygen in a metal lower than it in a reactivity series. Example : Reduction reaction Mg (s) + Cu. O Mg. O + Cu Oxidation reaction The substance that undergoes oxidation reaction is called a reducing agent. The substance that undergoes reduction reaction is called an oxidizing agent.

Chemical &Physical Properties of Oxygen Physical properties. • Colourless • No smell • Slightly soluble in water • Slightly denser than air Chemical properties. • Reaction with metals to form basic metal oxides. • Reacts with non-metals to form acidic non-metal oxides except water and carbon (II) oxide which are neutral

Uses of Oxygen. • Mountaineering • In hospitals to people with breathing problems • In steel making • Purification of metals such as iron from the ore • Rocket fuel • Oxy-hydrogen flame sued in wedding Rusting (hydrated iron (III) oxide) • Rust is reddish brown in colour

Conditions necessary for Rusting • Moisture (water) • Oxygen (air) Methods of preventing rust • Paintings, greasing and oiling • Coating with other metals • Plastic coating • Alloying • Silica gel • Sacrificial protection

Uses of Reactivity Series • Enables one to select suitable metals to be used as electrodes in cells • Used in sacrificial protection to prevent iron from rust.

UNIT FIVE WATER AND HYDROGEN

Specific Objectives -State the sources of water -Describe an experiment to show that water is a product of burning organic matter. -Describe an experiment to show that water contains hydrogen. -State the products of reaction of cold water and steam with different metals. -List the order of reactivity of metals as obtained from metal-water reaction. -Prepare hydrogen, investigate its properties and state its uses. -Define oxidation as oxygen gain and reduction as removal, of oxygen. -Explain metal oxide reactions with hydrogen in terms of reduction and oxidation.

Sources of Water Lakes, rivers, seas, oceans etc. Water as a product of burning organic matter.

Products of burning Candle Wax

• Points to note; • Candle wax is a hydrocarbon (organic compound) consisting of hydrogen and carbon atoms only. • When burned in air, the hydrogen atoms reacts with oxygen to form water which carbon atoms reacts with oxygen to form carbon iv oxide. • The vapour of water are condensed and collected as the colourless liquid in the set-up • Presence of carbon (IV) oxide are confirmed by use of calcium hydroxide solutions in which a white precipitate is formed. • ii) confirmatory test of water • Has no effect on litmus paper • Boils at 100 c at sea level • Change white anhydrous copper (II) sulphate to blue • Changes blue anhydrous cobalt chloride to pink

To Show that water Contains Hydrogen • Hydrogen is burnt in air. A colourless liquid (water) which boils at 100 c at sea level and turns white anhydrous copper (II) sulphate blue is formed. • Equation for the reaction • 2 H (g) + O 2 (g) 2 H 2 O (g)

Reaction of Sodium with Water.

• Equation Mg (s) + 2 H 2 O(l) Mg(OH)2 (aq) +H 2 (g) Zinc, iron and copper. • Do not react with cold water • Reaction of metals with steam

Reduction of Steam

Magnesium Reaction is fast Equation Mg (s) + H 2 O(g) Mg. O(s) +H 2 (g) Zinc and iron React slowly Equation Zn(s) + H 2 O (g) Zn. O(s) + H 2 (g) 3 Fe (s) + 4 H 2 O (g) Fe 2 O 4(s) + H 2 (g)

Reactivity Series Copper Does not react with steam. Order of reactivity series based on metal water reaction. K most reactive Na Ca Mg Al Zn Fe Pb Cu Least reactive

Important point to Note • Aluminum is more reactive than zinc and iron but does not react with steam because when exposed in air a layer of aluminum oxide which is insoluble in water is formed preventing the aluminum underneath from reacting with steam. • Aluminium is therefore used in making saucepans, Electric cables etc.

Laboratory Preparation of Hydrogen

A displacement reaction. Hydrogen is displaced from HCl by Zinc to form Zinc Chloride. Equation of Reaction: Zn(s) + 2 HCl (aq) Zn. Cl 2 (aq) + H 2 (g) Physical properties of hydrogen gas • Colourless • No smell • Insoluble in water • Less dense than air • No effect on litmus paper Test for hydrogen gas • A burning splint burns with pop sound in hydrogen gas.

Uses of Hydrogen • • • Manufacture of margarine Rocket fuel Manufacture of ammonia in the haber process Manufacture of HCl Welding (oxy-hydrogen flame) Weather stations balloons.

Reaction of Metal Oxides with Hydrogen Metal oxide reaction with oxygen

Reducing Properties of Hydrogen • Oxides of metals reduced by hydrogen are those oxides of less reactive metals: copper, zinc and lead. • Equations Cu. O(s) + H 2 (g) Cu(s) + H 2 O(l) Zn. O (s) + H 2(g) Zn(s) + H 2 O (l) Pb. O(s) + H 2 (g) Pb(s) + H 2 O(l)