1 CRACKING BGCSE CHEMISTRY WORD CRACKERS TUTORIALS Freedom Books Publishers ©Word Crackers Tutorials 2 All rights reserved including the right of reproduction in whole or in part in any form. No part of this publication may be reproduced, stored in a retrieval system or transmitted by any means, electronic, mechanical, photocopying or otherwise without prior written permission from the publisher. IT IS ILLEGAL TO PHOTOCOPY ANY PAGE IN THIS BOOK. Freedom Books Publishers PO Box 503441 Rail Park Mall Gaborone, Botswana Cell: (+267)73735611 Tel: (+267) 3104726 Email: freedombooksbw@gmail.com ISBN: 978-99968-437-0-9 © 2014 By Word Crackers Tutorials Freedom Books Publishers www.freedombooks.co.bw __________________________________________________________________________________ Writer: Moemedi Senwelo Cover design by: Olerile Garekwe ©Word Crackers Tutorials 3 Contents SEPARATION TECHNIQUES.............................................................................................................. 4 NATURE OF MATTER ......................................................................................................................... 4 ATOMIC STRUCTURE ........................................................................................................................ 5 PERIODIC TABLE ................................................................................................................................ 7 BONDING .............................................................................................................................................. 9 MOLES ................................................................................................................................................. 15 IONIC EQUATIONS............................................................................................................................ 18 CHEMICAL CALCULATIONS .......................................................................................................... 18 ACIDS, BASES AND ALKALIS ........................................................................................................ 19 ENERGY CHANGES .......................................................................................................................... 27 REVERSIBLE REACTIONS ............................................................................................................... 29 RATES OF REACTIONS .................................................................................................................... 30 REDOX REACTIONS ......................................................................................................................... 31 METALS .............................................................................................................................................. 32 ELECTROLYSIS ................................................................................................................................. 34 ORGANIC CHEMISTRY .................................................................................................................... 41 NON METALS ..................................................................................................................................... 46 CHEMISTRY IN THE ENVIROMENT .............................................................................................. 48 ABOUT WORD CRACKERS TUTORIALS ...................................................................................... 51 ©Word Crackers Tutorials 4 SEPARATION TECHNIQUES 1. Solute-A substance that dissolves in a solvent. 2. Soluble-Ability to dissolve in a solvent. 3. Solvent-A substance that can dissolve in a solute. 4. Solution-A mixture of a solute and a solvent. 5. Insoluble-A substance that cannot dissolve in a solvent. 6. Miscible-liquids which can mix e.g. water and ethanol. 7. Immiscible-liquids which cannot mix e.g. water and oil. 8. Separating funnel-a funnel used to separate miscible liquids. 9. Filtrate-The liquid which is obtained by filtration. 10. Residue-The particle remains on the filter paper after filtration. 11. Pure substance-a substance that does not contain any impurity. Pure substances have an exact melting and boiling point. 12. Filtration-A process used to separate solid particles from a liquid substance. 13. Decanting-A solid from liquid separation process whereby the solid settle at the bottom of the container and then the liquid is poured out. 14. Centrifuging-It is method whereby solid particles are small that they spread out and remain in suspension. 15. Evaporation–A process of heating a solution which there is a solvent dissolved in it. 16. Crystallisation-Using the sun to evaporate water and then obtain the saturated solution. 17. Fractional distillation-it is used to separate miscible liquids e.g. water and ethanol. 18. Simple distillation-it is used to separate a solvent from a solution e.g. salt from water. 19. Chromatography-it is used to separate solids that are soluble. PURE SUBSTANCE To test for purity of a substance check the melting and boiling point, if it varies from the actual points then the substance is not pure. NATURE OF MATTER STATE GAS LIQUID SOLID ©Word Crackers Tutorials ARRANGEMENT Particles are further apart Particles are close together Particles are tightly packed MOVEMENT Random Particles slide over each other Tiny vibrations at fixed points FORCES Very weak or no forces of attraction Weak forces of attraction Very strong forces of attraction 5 THE KINETIC PARTICLE THEORY OF MATTER It states that all matter is made up of tiny particles which are always in motion. It further states that when temperature of particles is increased their movement increases and when temperature is decreased the movement of particles decreases. DIFFUSION The movement of particles from a region of high concentration to a region of low concentration until all particles are evenly distributed. RATE OF DIFFUSION The rate of diffusion depends on molecular mass of atoms in reaction. Larger molecular mass atoms diffuse slowly while small molecular mass atoms diffuse faster. The lighter the particles of gas, the faster the gas will diffuse. Example: A particle of ammonia gas (17) has about half the mass of a particle of hydrogen chloride (36.5) so it will diffuse faster. The cloud formed when the two gases meet is nearer to the hydrogen chloride than the ammonia. ATOMIC STRUCTURE DEFINITION OF TERMS Proton-it is a positively charged particle of an atom. It is found in the nucleus of an atom. Electron-it is a negatively charged particle of an atom. It is located in the shells of the atom. Neutron-it is an uncharged particle of an atom. It is found in the nucleus of an atom. Atom-this is the smallest particle of an element. Element-a substance made of atoms of one kind. Molecule-a substance made of two or more atoms of the same or different elements. Compound-a substance made of two or more elements which are chemically combined. Mixture-a substance made of two or more elements which are physically combined. Isotopes-these are atoms of the same element with the same number of protons but different number of neutrons. Atomic number (proton number)-it is the number of protons in an atom. Mass number (nucleon number)-it is the total number of protons and neutrons. ©Word Crackers Tutorials 6 PARTICLE Electron Neutron Proton CHARGE -1 0 +1 SYMBOL e n p A.M.U 1/1840 1 1 NB: In a neutral atom the number of protons is equal to the number of electrons. ISOTOPES These are atoms of the same element which have same number of protons but different number of neutrons. OR these are atoms of the same element which have the same atomic number but different mass number. Example Chlorine has two isotopes (Cl35 and Cl37).Each has 17 protons and 17 electrons but one has 15 neutrons and mass number 35 while has 20 electrons an mass number 37. The 50:50 mixture of 35 Cl and 37 CI would have a relative atomic mass of 36. RELATIVE ATOMIC MASS (R.A.M) The average mass of a large number of atoms of an element is called Relative Atomic Mass, symbol (AR). ELECTRONIC CONFIGURATION The electrons in an atom move in a path called shells or orbitals around the nucleus. The first shell (nearest to the nucleus) can hold just two electrons. The electrons have less energy, because of the strong forces of attraction, because they are close to the nucleus. The second can hold electrons depending on the number of electrons for a particular element, so are the following shells. The atom with two electrons is stable when first shell is filled with two electrons. For example Helium is stable because it has two electrons in the outer shell. We say its electronic structure is stable; atoms do not take part in chemical reactions if the outer shell is full. These elements with full outer shells are called noble gases. They are unreactive because of their electronic structure and they are found in the same group of the periodic table. ©Word Crackers Tutorials 7 PERIODIC TABLE This is the table of elements arranged in an order of increasing atomic number consequently the relative atomic mass. Elements with the similar chemical properties fall in one group, so it can be said that the periodic table is the arrangement of elements according to their chemical properties. GROUPS A group also known as a family is a vertical column in the periodic table of the elements. The periodic table has 8 groups. In some groups the elements have very similar properties down the groups. All elements in a group have the same number of electrons in the outer shell. Metals always have a positive valency because they lose electrons while non-metals have a negative valency because they gain electrons. Many groups show similarities in certain features e.g. group 1, 2 and 3. PERIODS A period is horizontal row in the periodic table of the elements. Although groups are most common way of classifying elements periods can also be used. The periodic table has 7 periods. All elements in a period have the same number of shells and the number shells represent the period number. GROUP 1 The elements in group 1 are called alkali metals because they react with water to form alkali solutions. Alkali metals are the most reactive elements in the periodic table. This is because they have only one electron in the outer shell which makes it easier for them to lose it. Properties of alkali metals They are soft metals, can be cut with a knife. They react with water to give a flame. Their reactions with acids are highly explosive. They have low densities, melting and boiling points. Reactivity increases going down the group. They are stored under oil to prevent them from reacting with air and moisture. ©Word Crackers Tutorials 8 GROUP 2 They are called earth alkali metals. This is so because their compounds are quite common in rocks in the earth‟s crust. They are less reactive than group 1. TRANSITION METALS This is a block between group 2 and group 3. Properties of transition metals They and their compounds can be used as catalysts. They have variable valencies. They form coloured compounds. They have high melting and boiling points. They have high densities. They conduct electricity and heat. GROUP 7 They are also known halogens. All elements in this group are diatomic. Properties of halogens They are diatomic-exists as two atoms. They all form coloured vapours: Chlorine - green. Bromine - red/brown. Iodine - purple. They get darker going down the group. Melting points and boiling points are relatively low due to molecules been held together by weak inter-molecular forces. As you descend the group the melting and boiling point increases as the attraction between molecules gets larger. Halogens are very reactive. This is because halogens need to gain only 1 electron from another atom to gain more stability. Fluorine is the most reactive since the electron it is attempting to attract is coming into a shell closest to the positive nucleus. Greater attraction means that it is easier to gain an extra electron - therefore it is the most reactive. GROUP 8 ©Word Crackers Tutorials 9 They are also known as noble or inert gases. Elements in this group are unreactive since they have full number of electrons in the outer shell. Elements in this group are helium, neon, krypton, xenon and radon. Properties of noble gases They are non-metals. They are colourless. Density increases going down the group. They are unreactive. Uses of noble gases Helium is used to fill balloons. Argon is used in light bulbs to provide an inert atmosphere. Neon used to make advertising signs. BONDING COVALENT BONDING It is formed by two or more non-metals which share electrons. A covalent bond is held together by weak inter molecular forces. Properties of covalent bonds They are not soluble in water but soluble in organic solvents. They do not conduct electricity in any state. They have low melting and boiling points because of weak inter molecular forces. They form a simple molecular structure. Difference between inter and intra molecular forces Inter molecular forces exists between atoms (hold them together) and are very weak whereas intra molecular forces exist within atoms. IONIC BONDING ©Word Crackers Tutorials 10 It is a bonding between a metal and non-metal; atoms form ionic bonds by transferring electrons. Ionic bonds are held together by strong electrostatic forces. Properties of ionic bonds They have high melting and boiling points because of strong electrostatic forces. They conduct electricity when molten or dissolved in water because ions can easily move about. Most are soluble in water. NB: Ionic bonds in their solid state cannot conduct electricity because of strong electrostatic forces which does not allow flow of electrons. METALLIC BONDING In a metal, the atoms are very tightly packed, leaving little space between them. Atoms in a metal have at least one electron that is loosely held hence creating a 'sea' of electrons which why metals conduct electricity. ION It is an electrically charged particle. When an atom loses one or more electrons it becomes a positively charged ion. For example during the chemical reaction of sodium, each atom loses an electron to form a positive ion, Na+. When an atom gains one or more valency electrons it becomes a negatively charged ion. CATIONS It is a positively charged ion. This results from atoms losing electrons. ANIONS It is a negatively charged ion. This results from atoms gaining electrons. RADICLES Ions made up of more than one atom, e.g. NH4+. METALLIC CHARACTERISTICS This is the ability to lose valency electrons to form positively charged ions. It is also known as electro-positivity. Any atom with a net change (whether positive or negative) is called an ©Word Crackers Tutorials 11 ion. Metals donate electrons therefore they form positive ion, cations. Metallic character of elements decreases from left to right and increases right to left across the periodic table. Nonmetallic character is the ability of atoms to attract electrons towards their nucleus. Electronegativity increases on moving up the group and decreases on going down the group. EXAMINATION QUESTIONS 1. Complete the table below; State of matter Movement of particles [9] Arrangement of particles Forces of attraction Gas Liquid Solid 2. State the Kinetic Particle Theory of Matter. ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………….... [2] 3. What is diffusion? ………………………………………………………………………………………………… ………………………………………………………………..…………………………….. [2] 4. Explain why ammonia diffuses faster than hydrogen chloride gas. ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 5. Define the following terms; (a.) atom ……………………………………………………………………………………………… [1] (b.) molecule ……………………………………………………………………………………………… [1] (c.) element ……………………………………………………………………………………………… [1] (d.) electron ……………………………………………………………………………………………… [1] (e.) compound ………………………………………………………………………………………………… …………………………………………………………………………………………….... [1] (f.) mixture ………………………………………………………………………………………………… ……………………………………………………………………………………………… [1] (g.) atomic number ……………………………………………………………………………………………… [1] (h.) mass number ……………………………………………………………………………………………… [1] ©Word Crackers Tutorials 12 5. (a.) Draw an atom of sodium. [2] b. Complete the table below; [6] PARTICLE Electron Neutron Proton CHARGE -1 SYMBOL A.M.U n 1 c. Draw the structure of atoms of elements below in the periodic table showing the electron arrangement; [4] i. Calcium ii. Oxygen 6. a. What is an isotope? ………………………………………………………………………………………………… …………………………………………………………………………………………….... [2] b. Give three examples of pairs of isotopes. ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………….... [3] 7. a. State how elements are arranged in the periodic table. ……………………………………………………………………………………………… [1] b. What term is used to refer to; i. the vertical column of the periodic table ……………………………………………………………………………………………… [1] ii. The horizontal row of the periodic table ……………………………………………………………………………………………… [1] c. Describe the change in character across period III in terms of; i. Reactivity ……………………………………………………………………………………………… [1] ii. Density …………………………………………………………………………………………….... [1] ©Word Crackers Tutorials 13 iii. Boiling point ……………………………………………………………………………………………… [1] d. Element X has 7 shells, in which period does it lie in the periodic table? ……………………………………………………………………………………………… [1] 8. State two properties of the following; a. Transition metals ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] b. Halogens ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] c. Noble gases ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 9. State the uses of the following; a. sodium……………………………………………………………………………………. [1] b. calcium…………………………………………………………………………………… [1] c. neon………………………………………………………………………………………. [1] d. helium……………………………………………………………………………………. [1] e. argon………………………………………………………………………………………[1] 10. Name the method used to separate the following; a. ethanol from water…………………………………………………………………… [1] b. salt from water……………………………………………………………………….. [1] c. petrol from water…………………………………………………………………….. [1] d. soil from water……………………………………………………………………….. [1] 11. a. What is covalent bonding? ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] b. What is ionic bonding? ©Word Crackers Tutorials 14 ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 12. Draw the structures to show the bonding in the following; a. sodium chloride b. ammonia [3] [2] 13. Define the following; a. Metallic bonding ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] b. Radicle ……………………………………………………………………………………………… [1] c. Diatomic ……………………………………………………………………………………………… [1] d. Ion ……………………………………………………………………………………………… [2] e. Electro-negativity ………………………………………………………………………………………………… …………………………………………………………………………………………….. [2] f. Electro-positivity ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] ©Word Crackers Tutorials 15 MOLES The term mole refers to the value particles. This is known as Avogadro‟s constant. REACTING MASSES Example Calculate the mole of 60g of calcium carbonate, CaCO3. Find the mass of 0.4 moles of copper sulphate, CuSO4. MOLES AND VOLUME OF GASES 1 Mole of any gas at r. t. p occupies a volume of 24 dm3. 1dm3= 1000 cm3 ©Word Crackers Tutorials 1dm3= 1 Litre 16 Example Calculate the number of moles of oxygen molecules, O2 in the following volumes of oxygen gas. i) 48dm3 ii) 12dm3 i. ii. CONCENTRATION Example Calculate the concentration of 0.1dm3 of sodium hydroxide NaOH with 0.05 moles. ©Word Crackers Tutorials 17 EMPERICAL AND MOLECULAR FORMULAE Empirical formula is a simplified formula of a given compound e.g. Y3W15 will be YW5. Example 1. A hydrocarbon contains 92.3% of carbon. Its relative molecular mass is 78. Work out its a) Empirical formula b) Molecular formula Solution C % composition Mole ratio 92.3 7.7 7.76 7.7 1 1 Emperical Formula = CH Molecular Formula = (empirical formula) n Molecular Formula = (CH) 6 Molecular Formula = C6 H6 ©Word Crackers Tutorials H 18 IONIC EQUATIONS EXAMPLE Sodium hydroxide + hydrochloric acid → sodium chloride + water NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l) Na+ OH- (aq) + H+ Cl- (aq) → Na+ Cl- (aq) + H2O (l) Na+ OH- (aq) + H+ Cl- (aq) → Na+ Cl- (aq) + H2O (l) OH- (aq) + H+ (aq) → H2O (l) CHEMICAL CALCULATIONS PERCENTAGE YIELD PERCENTAGE PURITY ©Word Crackers Tutorials 19 ACIDS, BASES AND ALKALIS ACIDS Acids produce hydrogen ions (H+) as the only positive ion when dissolved in water. They are therefore said to be proton donors. PROPERTIES OF ACIDS - They have a sour taste. - Turns blue litmus paper red. - React with metal to form salt and hydrogen. - pH is less than 7. - React with bases to form salt and water. - All acids produce hydrogen ions H+. NB: The number 7 on the pH scale represents the conditions of pure water in relation to acidity and alkalinity i.e. the condition of exact neutrality. Universal Indicator and Litmus paper can be used to test alkalinity or acidity of a solution. WEAK ACIDS They ionise partially when dissolved in water. Not all the molecules actually break apart but only part fraction of acid molecules ionise. Colour range between yellow and orange. Examples: Carbonic acid (H2CO3), Citric acid, Ethanoic acid (CH3COOH), Lactic acid, Ascorbic acid. STRONG ACIDS Ionise completely when dissolved in water. All the molecules give out hydrogen ions. Produce a lot of H+. Examples: Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3) BASES A base is a proton acceptor. Bases that are soluble in water are called alkalis. ©Word Crackers Tutorials 20 PROPERTIES OF ALKALIS Acid + alkali salt + water An alkali reacts with ammonium salts to form salt and water. Alkalis turn red litmus paper blue. Alkali has pH value of greater than 7. STRONG BASES They completely ionise in water. E.g. NaOH →Na+ +OHWEAK BASES It partially ionise in solution i.e. form mainly molecules and few ions. E.g. NH3+H2O →OH- + NH+ CONCENTRATION AND STRENGTH Ethanoic acid is always classified as weak despite its concentration i.e. there is no relationship between concentration and strength. Indicator Colour in acidic Colour in neutral Colour in alkaline solution solution solution Blue litmus paper Red Blue Blue Red litmus Red Blue Blue Methyl Orange Pink Orange Yellow Phenothalaine Colourless Colourless Pink TYPES OF OXIDES BASIC OXIDES –MgO, CuO, NaO-few are soluble. ACIDIC OXIDES-SO4, SO3, CO2,-react with alkalis to give salt and water. NEUTRAL OXIDES –H2O, NO, CO AMPHOTERIC OXIDES –ZnO, Al2O3, PbO ©Word Crackers Tutorials 21 ACID RAIN It is caused when sulphur dioxide and nitrogen oxide gases are released into the air. When they dissolve in the water droplets and fall to earth as rain or snow. BEHAVING AS A BASE ZnO + 2HNO3→ Zn (NO3)2 + H2O BEHAVING AS AN ACID ZnO + NaOH→ NaZn + H2O (Sodium Zincate) TYPE OF OXIDE REACTION WITH HCL REACTION WITH NaOH Basic e.g. CuO Reaction No reaction Acidic, SiO2 No reaction Reaction Neutral, CO No Reaction No Reaction Amphoteric, ZnO Reaction Reaction SOLUBILITY IN WATER Generally organic compounds do not dissolve in water, while non-organic/inorganic compound dissolve in water, but not all inorganic compounds are soluble in water. SOLUBILITY RULES-INSOLUBLE COMPOUNDS All carbonates except group 1 metals and ammonium carbonates. All hydroxides except those of group 1 metals and those of Ca, Sr and Ba. All sulphates of Barium, Calcium and Lead SOLUBLE COMPOUNDS All compounds and complexes of group 1 metals and ammonium All nitrates All sulphates except those of Barium, Calcium & Lead, sulphates of Barium and Calcium are sparingly soluble upon warming. All group 1 oxides. All phosphates. ©Word Crackers Tutorials 22 Most chlorides, bromides and iodides are soluble. Some exceptions are those of lead, barium and silver. METHODS OF PREPARING SOLUBLE SALTS 1) TITRATION It is used to prepare a soluble salt from a soluble base such as sodium hydroxide or sodium carbonate and an acid. This method is used to make salts of group 1 metals and ammonium. 2) NEUTRALISATION- of an insoluble base by an acid An excess of the base is added to an acid and the excess of the base is removed by filtration. The filtrate is partially evaporated to obtain crystals of salt. Soluble salts of most of the other elements are made by this method. 3) METAL REACTING WITH ACID This method is essentially the same as one as one above. The reaction is not neutral but redox. The method can be used to make magnesium, zinc, aluminium and iron (ii) salts. It cannot be used to prepare salts of very reactive metals such as sodium, potassium, because they react explosively with acids. PREPARATION OF AN INSOLUBLE SALT Precipitation method is used to prepare an insoluble salt. Two soluble solutions are mixed together to give one soluble and one insoluble salt. The two are separated by filtration. EXAMPLE: Reacting an INSOLUBLE BASE with AN ACID. 1) Copper (ii) oxide is an insoluble black powder. Copper (ii) oxide is added to hot dilute sulphuric acid until it is in excess. The reaction is very slow when the acid is cold. Reaction: CuO + H2SO4→CuSO4 + H2O 2) Excess copper (ii) oxide is removed by filtering. 3) Copper sulphate solution is heated until it is saturated. The solution is cooled to form crystals. Crystals are then dried. ©Word Crackers Tutorials 23 REACTING A METAL AND AN ACID All metals react with at least one acid. This method can therefore be used on a number of metals. Some unreactive metals need very strong, concentrated acids and only react very slowly. Other very reactive metals explode dangerously with acids. It is best to use this method with moderately reactive metals. Metal + acid → salt + Hydrogen Example 1. Magnesium powder is added to dilute acid until the reaction stops. Reaction: Mg + H2SO4→MgSO4 + H2 2. Excess magnesium is removed by filtration. 3. Magnesium Sulphate solution is heated to evaporate off excess water. Solution is heated until it is saturated. 4. Saturated magnesium sulphate solution is boiled so that crystals form. 5. They crystals are then air dried. REACTING A CARBONATE WITH AN ACID All carbonates react with acids to give out water, salt, and carbon dioxide. Example: Reaction: CuCO3 + HCl → CuCl + H2O + CO2 1. Copper (ii) carbonate is an insoluble green powder. It is added to dilute hydrochloric acid until it is in excess. 2. Excess copper (ii) carbonate is removed by filtering. 3. Solution is heated until it is saturated. 4. Saturated solution is cooled so that it crystallises. 5. Crystals are pressed dry with filter paper. ©Word Crackers Tutorials 24 EXAMINATION QUESTIONS 1. a. Calculate the moles the following; i. 20g of sodium. [3] ii. 5g of magnesium [3] iii. 20dm3 of oxygen [3] iv. 0.5mol/dm3 of sodium chloride with volume 20cm3. [3] 2. Define the following terms; a. An acid …………………………………………………………………………………………………. ……………………………………………………………………………………………… [2] b. A base ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] c. Strong alkali ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] d. Weak acid ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 3. a. Give three properties of acids. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………… [3] ©Word Crackers Tutorials 25 b. Give three properties of alkalis. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………… [3] 4. a. What are the results for following tests of acid? i. Methyl orange…………………………………………………………………………..… [1] ii. Universal indicator.......………………………………………………………………….. [1] iii. Red litmus paper……...…………………………………………………………………. [1] b. What are the results for following tests of alkali? i. Methyl orange…………………………………………………………………………..… [1] ii. Universal indicator....…………………………...……………………………………….. [1] iii. Red litmus paper……………………………...…………………………………………. [1] 5. What is pH? ……………………………………………………………………………………………… [1] 6. Complete the equation below. Hydrochloric acid + sodium carbonate = ______________+___________+____________[3] 7. Describe the test for; i. Hydrogen test……………………………………………………………………………………………… result………………………………………………………………………………………... [2] ii. Carbon dioxide test…………………………………………………………………………………………….... result……………………………………………………………………………………….. [2] 8. Complete the equation below. Sodium hydroxide + ammonium sulphate= __________+___________+_____________ [3] 9. Give two applications of acid/base reactions in daily life. ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 10. Give one example of the following; a. Acidic oxide……...…………………………………………………………………….... [1] b. Basic oxide…....…...…………………………………………………………………….. [1] c. Neutral oxide…..………………………………………………………………………… [1] d. Amphoteric oxide...……………………………………………………………………… [1] 11. Describe how crystals can be obtained from a solution of copper sulphate. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………… [3] ©Word Crackers Tutorials 26 12. What are the tests and results for the tests for the following ions: a. Iodide ions ...……………………………………………………………………………………………… ……………………………………………………………………………………………… [3] b. Nitrate ions ………………………………………………………………………………………………… ……………...………………………………………………………………………………. [3] c. iron (ii) ions ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] d, iron (iii) ions ………………………………………………………………………………………………… ………………..…………………………………………………………………………….. [2] 13. Match the following cations with the effect that is seen when they are reacted with aqueous sodium hydroxide/ammonia. CATION Copper(II) Iron (III) Iron(II) Ammonium Zinc [5] EFFECT Light blue precipitate Ammonia gas produced White precipitate soluble in excess Dirty green precipitate Reddish brown precipitate 14. During an experiment a student releases a gas inside a fume cupboard. The student does not know which gas is it. Describe different tests on how the student might identify the gas released. a) Oxygen ………………………………………………………………………………………… …………………………………………………………………………………….. [2] b) Ammonia ………………………………………………………………………………………… …………………………………………………………………………………….. [2] c) Chlorine ………………………………………………………………………………………… ……………………………………………………………………………………… [2] d) Hydrogen ………………………………………………………………………………………… …………………………………………………………………………………….... [2] e) Carbon dioxide ………………………………………………………………………………………… ……………………………………………………………………………………… [2] ©Word Crackers Tutorials 27 ENERGY CHANGES EXOTHERMIC REACTIONS 1) Reaction gives out heat to the surrounding 2) The chemical energy of the reactants is bigger than that of the product 3) Examples are Respiration, Hydration, Neutralisation Reaction, Combustion/burning. ENDOTHERMIC REACTIONS 1) Reaction absorbs heat energy from the surroundings 2) The chemical energy of the reactants is smaller than that of the product 3) Examples are Photosynthesis, Decomposition, Dehydration and Melting. BOND BREAKING AND BOND FORMATION BOND BOND ENERGY kJ/mol C-H 413 F-F 158 H-F 565 C-F 495 Calculate the energy for bonds broken and bonds formed for the reaction CH4 + F2 → CH3F + HF CALCULATING BOND BREAKING ENERGY C-H × 4 413 × 4 = 1652 kJ/mol F-F 158 × 1 = 158 ©Word Crackers Tutorials 28 Total bond breaking energy 1652 + 158 = 1810kJ/mol CALCULATING BOND FORMATION ENERGY C-H × 3 413 × 3 = 1239kJ/mol C-F × 1 495 × 1 = 495kJ/mol H-F × 1 565 ×1 =565kJ/mol Total bond formation energy 1239 + 495 +565 = 2299kJ/mol Energy change = bond breaking energy – bond formation energy Energy change = 1810 – 2299 Energy change = -489kJ/mol Since its negative, it is an endothermic reaction. ©Word Crackers Tutorials 29 REVERSIBLE REACTIONS It is a reaction that can proceed both ways. The reaction can go forward or backward depending on the conditions of reaction. Reactants form products while products decompose to form the original reactants. Dynamic equilibrium-this is whereby the rate of the forward reaction is equal to the rate of the reverse reaction. LE CHATELIER’S PRINCIPLE When a change is made to the conditions of a closed system in dynamic equilibrium, the system moves so as to oppose that change. CONDITIONS THAT AFFECT REVERSIBLE REACTIONS 1. Concentration- If reactants are added or products removed at equilibrium the forward reactions is favoured hence more products are formed. 2. Temperature-When temperature increases an endothermic reaction is favoured. Lowering temperatures favours an exothermic reaction. 3. Pressure (for gaseous reactions)-Has no effect if the number of moles is the same in both sides (products and reactants). For different number of molecules increasing pressure favours a reaction that produce less molecules while reducing pressure favour a reaction that produce more molecules. 4. Catalyst- It does not change equilibrium but ensures that equilibrium is attained quickly. ©Word Crackers Tutorials 30 RATES OF REACTIONS It measures the speed at which reactants change into products. FACTORS THAT AFFECT REACTION To understand how different factors determine the reaction rate, first understand the collision theory. COLLISION THEORY A reaction will occur when particles collide and they have enough energy to react. Reaction depends on the collision rate of the reactant particles and the energy of these particles. 1. CONCENTRATION When concentration is increased, the rate will increase. When concentration is decreased, the rate will decrease. Increasing the concentration of a reactant increases the number of particles in unit volume, so there will be more collisions hence the rate of reaction increases. 2. TEMPERATURE When temperature is increased, the rate will increase. When temperature is decreased, the rate will decrease. When temperature is increased the particles have more energy to move. As the particles move faster they collide more frequently hence increasing the rate of reaction. 3. PRESSURE The pressure only affects reactions affecting gases. When pressure is increased, the rate will increase. When pressure is decreased, the rate will decrease. Increasing pressure brings gas particles close together hence they collide more frequently hence increasing the rate of reaction. 4. CATALYST A catalyst increases the rate of reaction but remains chemically unchanged. ©Word Crackers Tutorials 31 5. PARTICLE SIZE Only affects reactions involving solids. The larger the particle, the lower the rate of reaction and the smaller the particle, the higher the rate of reaction. Small particles i.e. powders have larger surface area as compared to blocky particles. 6. LIGHT INTENSITY When light intensity is increased, the rate of reaction will increase. When light intensity is decreased, the rate will decrease. REDOX REACTIONS Redox stands for Reduction/Oxidation reactions. OXIDATION REDUCTION Gain of oxygen Loss of oxygen Loss of electron(s) Gain of electron(s) Increase in oxidation number Decrease in oxidation number Example CuO + H2 → Cu + H2O CuO has lost oxygen, therefore it has been reduced to Cu. CuO is an oxidising agent or oxidant. H2 has gained oxygen, therefore it has been oxidised to H2O. H2 is a reducing agent. TEST FOR OXIDISING AND REDUCING AGENTS OXIDISING AGENT COLOUR CHANGE Potassium Iodide Colourless to yellow-brown REDUCING AGENT COLOUR CHANGE Acidified Potassium Manganite Purple to Colourless Acidified Potassium Dichromate Orange to green ©Word Crackers Tutorials 32 METALS REACTIVITY SERIES K, Na, Mg, Al, *C, Zn, Fe, Pb, *H, Cu, Ag, Au, Pt Decreasing Reactivity→ *Non-metals are included for convenience. Ag, Au, Pt-Do not react with oxygen. USES OF METALS AND ALLOYS Brass-made of Cu and Zn, used to make jewellery, furniture, machine bearings. Bronze-Made of Cu and Tin used to make castings and machine parts. Cupro-nickel-Copper and nickel-used to make turbine blades Duralumin-made of Al, Cu, Mg, Mn, Fe-it is used to make aircraft parts, bicycle parts Pewter-Lead, Tin, Antimony, used to make plates, ornaments, drinking mugs, electrical wires. Cast iron-Fe, C, Si, P, S, used to make railings, hot water pipes, Bunsen burner, melts at lower temperatures. Wrought Iron-Used to make iron nails, sheeting, horseshoes, agriculture implements, it has high melting point, it is malleable. Steel- Fe, C-it is hard and strong hence it is used to make automobile bodies, wire mesh, stainless steel cutlery. EXTRACTION OF METALS FROM THEIR ORES ORE- a rock that contains an element as a compound or a “free metal” METHODS OF EXTRACTION ©Word Crackers Tutorials 33 ELEMENT METHOD OF EXTRACTION K, Na, Cu, Mg The anhydrous Cl- it is melted and electrolysed. Al The anhydrous oxide is melted and electrolysed Zn, Fe, Pb, Cu , they are found as sulphates and oxides. The sulphates are reacted to give oxides. The oxides are reduced with carbon. Ag, Au, Pt - Found „native‟ as free metals. EXTRACTION OF IRON: BLAST FURNACE Haematite- Fe2O3, is the common ore of iron. CHEMICAL REACTIONS 1) C+ O2 → CaO + CO2 Coke burns producing huge amounts of heat. 2) CaCO3 →CaO + CO2 Limestone is decomposed 3) CO2 + C → 2CO Higher up the furnace the oxygen has been used up and CO2 is reduced to carbon monoxide. 4) Fe2O3 (s) + 3CO (g) → 2Fe (l) + 3CO2 (g) Carbon monoxide reduces the Fe2O3 to iron which flows down to the bottom of the furnace. 5) CaO + SiO2 → CaSiO3 (sand) Waste gases-can be recycled in the furnace or used for industrial heating. Slag-(CaSiO3)-it is used for road surfacing. MOLTEN IRON The iron form blast furnace has some impurities mostly carbon. It is called cast iron. The excess carbon is removed by basic oxygen furnace. C (g) + O2 (g) → CO2 (g) Carbon dioxide then escapes as a gas. ©Word Crackers Tutorials 34 ELECTROLYSIS Electrolysis- The process of passing an electric current through a substance and bringing about a chemical reaction. Electrolyte-It is substance that conducts an electric current when molten or dissolved in water. Weak electrolyte-it is poor conductor of electricity because it is only partially ionised- many molecules and fewer ions. Electrodes- Pieces of metal or carbon through which the current enters and leaves the electrolyte. Positively charged electrodes are called anode and negatively charged electrode are called cathode. ELECTROLYSIS CURCUIT 1) Electrons flow from battery /power source to the cathode. 2) Positive ions in the electrolyte are attracted to the negative electrode. 3) The positive ions accept electrons from the cathode and metals or hydrogen are formed at the cathode. 4) Electrons flow from the anode to the battery /power supply. 5) Negative ions (non-metals except hydrogen) are attracted to the positive electrode. 6) When the anode is inert (carbon/graphite or platinum) the negative ions lose electrons to the anode. When the anode is not inert (Ag, Cu, more reactive metals) the metal atoms of the anode lose electrons and form positive ions. The anode will dissolve and decrease. All aqueous solutions contain OH- and H+ in addition to ions from the electrolyte. DISCHARGE OF IONS The lower in each of the series will be discharged. The order for positive ions is very similar to the reactivity series of metals. ©Word Crackers Tutorials 35 ANION REACTIVITY SERIES SO42-, NO3-, OH-, Cl-, Br-, IWhen the anode is not inert, it will lose electrons and form positive ions in preference to the discharge of a negative ion. EXAMPLES OF ELECTROLYSIS ELECTROLYSIS Electrode Ions present Reaction with anode Reaction with cathode Overall reaction Conclusion MOLTEN SODIUM CHLORIDE Inert carbon/graphite Na+ and ClCl- - 2e → Cl2 Na+ + e → Na 2Cl- + 2Na+ → Cl2 + 2Na sodium chloride has decomposed to form Cl2 gas and metal sodium. ELECTRO-PLATING This is used to place one metal on another. The metals that are commonly used to electroplate are copper, chromium, nickel, tin, gold and silver. Reasons for electroplating are for appearance, protection from corrosion and abrasion. PRINCIPLES 1. The object that is being electroplated form the cathode. 2. The metal used for plating is the anode. 3. The electrolyte-solution of metal used to plate. Example-plating a kitchen folk with Tin Reaction at the Anode Sn (s) – 2e → Sn2+ (aq) Reaction at the Cathode Sn2+ (aq) + 2e → Sn (s) REFINING Metals can be refined or purified by electrolysis. The impure metal forms the anode, the cathode is a small piece of pure metal and the electrolyte is an aqueous metal salt. Example Copper refining At the cathode: Cu2+ + 2e →Cu (s) At the anode: Cu - 2e →Cu2+ (s) ©Word Crackers Tutorials 36 EXTRACTION OF ALUMINIUM FROM ITS ORE i. ii. iii. iv. v. vi. vii. The main ore of aluminium is bauxite which is changed into pure aluminium oxide, Al2O3. Both cathode and anode are carbon (graphite). The electrolyte is a molten mixture of aluminium oxide dissolved in cryolite, Na3AlF6. Cryolite lowers the melting point of the electrolyte-this saves energy and reduces costs. Reaction at the cathode Al3+ (aq) + 3e → Al (s) Reaction at the anode 2O2- (g) + 4e → O2 (g) The carbon anode burn in the oxygen so they have to be replaced periodically. The cryolite lowers the temperature from over 2 C melting point of aluminium oxide to about C. ow temperature improves electrical conductivity of the electrolyte. PROPERTIES OF ALUMINIUM AND ITS USES PROPERTIES Conducts heat and electricity. It has a low density as compared to other metals. It does not corrode. Reacts with air to form its oxides and nitrides. Reacts with acid slowly and liberates hydrogen rapidly. USES Making electrical cables Making cooking pots Aeroplane bodies Cooking pots and foil PROPERTIES ENABLING Ductile Malleable Low densities High melting point ELECTROLYSIS CALCULATIONS Faraday‟s first law of electrolysis states The mass of a substance liberated at an electrode during electrolysis is proportional to the quantity of electricity passing through the electrolyte. QUANTITY OF ELECTRICITY FARADAY‟S CONSTANT It is the amount of electricity carried by 1 mol of electrons, that is 1 mole of electrons carry an electrical charge of 96 500C. 96 5 ©Word Crackers Tutorials C is Faraday‟s constant 1 mol: 96 500C 37 EXAMINATION QUESTIONS 1. Define the term dynamic equilibrium. ……………………………………………………………………………..…………… ……………………………………………………………...………………………. [2] 2. State and explain two conditions that would favour the; i) Endothermic reaction …………………………………………………………………………………… ……………………………………………………………………………...… [2] ii) Exothermic reaction …………………………………………………………………………………… ………………………………………………………………………………... [2] 3. N2 + 3H2 → 2NH3 *H-92kj/mol True or False i) The rate of the forward reaction is equal to the rate of reverse reaction. …………………………………………………………………………..…. [1] ii) The amount of reactants is equal to the amount of products. ……………………………………………………………………………… [1] iii) What can be done to increase the amount of ammonia formed? ………………………………………………………………………………………… ………………………………………………………………………...……………. [2] iv) State the 4 conditions that can be altered so that equilibrium shifts. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………..….. [4] v) What is meant by a reversible reaction? ………………………………………………………………………………………… ……………………………………………………………………………………… [2] 4. Name one iron ore and write its formula. ……………………………………………………………………………………… [1] a. Which substance acts as a reducing agent in the reaction with iron oxide in the blast furnace? …………………………………………………………………………………..….. [1] b. What is the chemical name of slag? ……………………………………………………………………………………… [1] ©Word Crackers Tutorials 38 c. Why is molten iron extracted at the bottom in the blast furnace? ……………………………………………………………………………………… [1] d. Calculate the relative atomic mass of iron oxide Fe2O3. i) Calculate the percentage by mass of iron that could be extracted from 1000kg of iron oxide. [3] e. In the blast furnace limestone decomposes into 2 products namely CaCO3 (s) → ……………………..…… + ………………………………… [2] f. Reduction of Fe2O3 by carbon monoxide forms iron, balance the equation below. ___ Fe2 O3(s) +__ CO (g) → __Fe (l) + __CO2 (g) g. Complete the table below by matching the metal with its ore. Metal Ore Magnetite Zinc Bauxite Copper h. Match the metal with method of extraction. METAL Sodium Lead Silver Aluminium i. METHOD OF EXTRACTION Usually found as pure Anhydrous oxide is melted and electrolysed Sulphide is roasted to give oxide and then reduced with carbon Anhydrous chloride is melted and electrolysed Action of heat on metal nitrates, complete equations below. a) ___Zn(NO3)2 (s) → ___ ZnO (s) + ____+ O2 (g) [2] b) 2Cu(NO3)2 (s) → ___________ + ___________ [2] ©Word Crackers Tutorials 39 j. What is an alloy? ……………………………………………………………………………………… [1] 5. Define the following terms. a. Electrolysis ………………………………………………………………………………………… ……………………..……………………………………………………………..… [2] b. Electroplating ………………………………………………………………………………………… ……………………………………………………………………………………… [2] c. Electrode ………………………………………………………………………………………… ……………………………………………………………………………………… [2] d. Electrolyte ………………………………………………………………………………………… ……………………………………………………………………………………… [2] 6. Draw a set up to show how a plastic key can electroplated with zinc and describe brief what will happen. ……………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………….. [6] 7. State 2 reasons for electroplating ………………………………………………………………………………………… …………………………………………………………………………………….. [2] 8. In an electrolysis experiment, current of 19.1 A was passed through the cell for 1 minute 30 seconds. i) How many coulombs were passed? [3] ©Word Crackers Tutorials 40 ii) Calculate the number of Faradays 1 Faraday = 96500 C [2] iii) Calculate number of moles produced. [2] 9. Electrolysis of the cathode and anode: complete the following; i. a. b. c. d. Electrolyte: aqueous copper (II) sulphate Electrode: carbon Ions present: ……………………………………………………… [2] Reaction at cathode: ……………………………………………… [2] Reaction at anode: ………………………………………………... [2] Overall reaction: ………………………………………………….. [1] 10. A blacksmith coats a watch with silver by using it as an electrode in an electrolysis experiment. The electrolyte was a solution of silver salt. Current of 0.5A flowed for 30 minutes. a) Name the electrode formed by the watch. ……………………………………………………………………. [1] b) Calculate total charge in coulombs. [2] c) Use the answer above to calculate moles of electrons that passed through the circuit. [2] d) How many moles of silver were deposited ; Ag + e) What mass of silver was deposited? ©Word Crackers Tutorials [2] [1] 41 ORGANIC CHEMISTRY EXAM TIPS: You should, Be able to state the general characteristics of a homologous series. Name and draw the structures of unbranched alkanes, alkenes, alkanols, and alkanoic acids up to five carbon atoms. Be able to identify alkanes, alkenes, alkanols, and alkanoic acids when given their structural formulas. Draw isomers up to five alkanes. State and describe the reactions of alkanes. Name the source of alkanes Name each fraction and its use. Describe properties of alkenes in terms of burning, polymerisation, addition reactions with bromine, hydrogen and steam. Distinguish unsaturated hydrocarbons e.g. alkenes from saturated hydrocarbons e.g. alkanes by molecular structures and by using aqueous bromine. Describe the formation of poly(ethene) as an example of addition polymerisation of monomer units, list some uses of poly(ethene) e.g. plastic bags. describe the fermentation of simple sugars to produce ethanol (and carbon dioxide) and its importance in brewing and baking Prepare ethanol by fermentation; describe formation of ethanol by catalytic addition of steam to ethene. List some uses of alcohols as solvents, as fuels and as constituents of alcoholic beverages. Describe the formation of alkanoic acids [exemplified by the formation of Ethanoic acid by the oxidation of ethanol by atmospheric oxygen and by acidified potassium chromate (VI)/potassium manganate (VII)] explain properties of ethanoic acid as a typical weak acid name some commonly occurring alkanoic acids, their sources and uses e.g. tartaric acid, Ethanoic acid, ascorbic acid, citric acid describe the reaction of ethanoic acid with ethanol to give an ester (ethyl ethanoate) Be aware of macromolecules as large molecules built from small units. be aware of the formation of synthetic polymers and their impact in everyday life list some typical uses of condensation polymers and link their properties to uses Describe the pollution problems caused by non-biodegradable polymers e.g. plastics, nylon. List some typical uses of man-made fibres Advantages and disadvantages of synthetic and natural fibres describe uses of different macromolecules as related to their general structure and properties e.g. PVC, Polystyrene, Polypropene interpret polymerisation reactions in terms of simple graphical formulae ©Word Crackers Tutorials 42 describe the formation of nylon and terylene using simplified structure understand the impact of natural macromolecules in our daily life name proteins, fats and carbohydrates as the main constituent of food describe the hydrolysis of proteins to amino acids prepare soap by hydrolysis of fats describe complex carbohydrates as macromolecules formed by the condensation polymerisation of smaller carbohydrate units called sugars describe the hydrolysis of complex carbohydrates (e.g. starch) to give simple sugars describe proteins as possessing the same linkage (amide) as nylon but with different units describe fats as esters possessing the same linkage as Terylene but with different units demonstrate how chromatography techniques can be applied to colourless substances by exposing chromatograms to substances called locating agents (refer to Rf factor) or UV light describe, in outline, the usefulness of chromatography in separating and identifying the products of hydrolysis of carbohydrates and proteins. Note: Points written in bold are for pure sciences only. ©Word Crackers Tutorials 43 EXAMINATION QUESTIONS 1. Define the following terms; a. Homologous series ………………………………………………………………………………………………..… …………………………………………………………………………………………….... [2] b. Hydrocarbon ………………………………………………………………………………………………….. .……………………………………………………………………………………………... [2] c. Isomers ………………………………………………………………………………………………….. .……………………………………………………………………………………………. [2] d. Structural formula ………………………………………………………………………………………………….. ………………...………………………………………………………………………….… [2] e. Polymerisation ……….………………………………………………………………………………………… ……………………………………………………………………………………………… [2] 2. a. Draw and name the isomers of butane C4H10. [4] b. State two properties of a homologous series. ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] c. State the uses of the following; [4] i. Petrol fraction ………...……………………………………………………………………………………. [1] ii. Kerosene………………………………………………………………………………… [1] iii. Bitumen…………………………………………………………………………………. [1] iv. Diesel oil………………………………………………………………………………… [1] d. State the two reactions of alkanes. ………………………………………………………………………………………………… ……………………………………………………………………………………………… [2] ©Word Crackers Tutorials 44 2. a. Bromine reacts with ethene to change colour. State the colour changes. ……………………………………………………………………………………………… [2] b. Name two methods which are used to obtain ethanol. ………………………………………………………………………………………………… ……………………………………………………………………………..……………..… [2] c. What are the conditions needed for hydration of ethene to ethanol. ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………….. [3] d. Name the two products formed when ethanoic acid reacts with ethanol. ………………………………………………………………………………………………… …………………………………………………………………………………………….. [2] 3. a. State four groups in the homologous series. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………….. [4] 4. Name any five macromolecules. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………… [5] 5. What products are formed from the combustion of an alkane? ………………………………………………………………………………………… ……………………………………………………………………………………… [2] 6. What is meant by cracking? ……………………………………………………………………………………… [1] 7. Complete the equation to show 2 compounds that may be formed when pentane is cracked. C5H12 → __________ + __________ ©Word Crackers Tutorials [2] 45 8. Nylon is a synthetic condensation polymer. a) Name the linkage in nylon. …………………………………………………………………………….... [1] b) Name one natural macromolecule similar in the structure to nylon. ……………………………………………………………………………… [1] c) Name one environmental problem that can be caused by the use of nylon, explain your answer. ………………………………………………………………………………… ……………………………………………………………………………… [2] 9. a) Butane is used as a fuel for cooking. Why would it be dangerous to burn butane in a limited supply of oxygen? ……………………………………………………………………………………… [1] b) To which homologous series does the structure belong to? ……………………………………………………………………………………… [1] c) State 2 chemical properties of all the substances in the homologous series. ……………………………………………………………………………………………… ………………………………………………………………………………………….. [2] 10. Proteins are natural macromolecules made up of amino acids monomers, by condensation polymerization. The monomers are joined together by amide linkages which can be broken down by hydrolysis. Define the following terms; i. Macromolecule ……………………………………………………………………………………… ………………………………………………………………………………..… [2] ii. Hydrolysis ……………………………………………………………………………………… ………………………………………………………………………………….. [2] 11. Why is concentrated H2SO4 used in the process of esterification? …………………………………………………………………………………….... [1] 12. a. What is saponification? ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………………… [3] b. Name any two products formed from saponification. ………………………………………………………………………………………… …………………………………………………………………………………….. [2] ©Word Crackers Tutorials 46 NON METALS EXAM TIPS: Describe the preparation of chlorine from concentrated hydrochloric acid using an oxidising agent State the test for chlorine State the uses of chlorine (sterilising water, manufacturing plastics, making domestic bleaches etc. Describe properties of chlorine Describe the bleaching action of chlorine Understand the uses of some important compounds of chlorine and its manufacture Name some sources of sodium chloride e.g. sea water, salt pans (give examples of some places in Botswana) Describe the importance of sodium chloride as a source for chlorine, sodium hydroxide and common salt Describe extraction of sodium chloride from soda ash (focus on local process at Botswana Ash in Sowa Town) Acquire knowledge of sources and uses of sulphur and properties of its important compounds List the sources of sulphur, describe the preparation of sulphur dioxide, state the important uses of sulphur dioxide (bleach in the manufacture of wood pulp, food preservative by killing bacteria) Describe the manufacture of sulphuric acid from sulphur by Contact process (conditions and reactions) Describe the properties of dilute sulphuric acid, state the important uses of sulphuric acid (in the manufacture of detergent and fertilisers, car batteries and as a dehydrating agent) Know the different forms of carbon; state diamond and graphite as allotropes of carbon Relate the structures of diamond and graphite to their uses Describe the processes involved in the extraction and refining of diamond in Botswana Compare the structure of graphite, diamond and silica [silicon (IV) oxide] Describe the similarity in structure of diamond and silica [silicon (IV) oxide] and of their properties related to their structures. Acquire knowledge of formation and uses of important carbonates List the uses of sodium carbonate and calcium carbonate Describe the manufacture of sodium carbonate by Solvay process Acquire knowledge of sources and uses of nitrogen Name the sources of nitrogen and hydrogen in making ammonia State the uses of ammonia Describe the essential conditions for making ammonia by the Haber process Describe the essential conditions for making nitric acid by the Ostwald process ©Word Crackers Tutorials 47 EXAMINATION QUESTIONS 1. Describe the test for chlorine. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………….. [3] 2. State four uses of chlorine. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………………… [4] 3. Give two chemical properties of chlorine. ………………………………………………………………………………………… ……………………………………………………………………………………... [2] 4. State two uses of sulphur dioxide. ………………………………………………………………………………………… ……………………………………………………………………………………... [2] 5. Explain why graphite is a good conductor of electricity. ………………………………………………………………………………………… ……………………………………………………………………………………… [2] 6. State two uses of calcium carbonate. ………………………………………………………………………………………… …………………………………………………………………………………...…. [2] 7. State two uses of sodium carbonate. ………………………………………………………………………………………… ……………………………………………………………………………………... [2] 8. State the source of nitrogen and hydrogen in making ammonia. Nitrogen …………………………………………………………………………… [1] Hydrogen ………………………………………………………………………….. [1] 9. State three properties of silicon IV oxide. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………….... [3] 10. State two conditions necessary for the Haber process. ………………………………………………………………………………………… ……………………………………………………………………………………… [2] 11. State two conditions necessary for the Contact process. ………………………………………………………………………………………… …………………………………………………………………………………...…. [2] ©Word Crackers Tutorials 48 CHEMISTRY IN THE ENVIROMENT EXAM TIPS: Acquire knowledge about the physical and chemical properties of water Investigate physical properties of pure water, carry out a chemical test for water Explain the following terms hydration, hydrolysis, drying, dehydration deliquescence, efflorescence and hygroscopic Understand water of crystallisation Appreciate the effect of dissolving property of water in producing hard water and pollution Describe the process that results in hard water (name salts causing hard water) Distinguish temporary hardness of water and permanent hardness of water Measure the hardness of water Describe physical and chemical process of softening hard water Describe how a detergent works Describe pollution of water in terms of dissolved substances, accumulation of toxic substances and effect of detergents Investigate effects of pollutants in water Explain the consequence of water pollution Describe pollution of water in terms of biological oxygen demand (BOD Appreciate the delicate balance of air in volume and quality State the proportions of different components of clean air by percentage volume Describe the separation of oxygen and nitrogen from air by fractional distillation Explain the effect of increased carbon dioxide concentration in the atmosphere Name the uses of oxygen in health and in industry State the importance of the ozone layer Name the common pollutants in the air as carbon monoxide, sulphur dioxide, oxides of nitrogen and lead compounds State the source of each of the common pollutants Explain why it is dangerous to run a petrol engine in a closed garage or use a coal fire in a closed room Explain the presence of oxides of nitrogen in car exhausts Explain the problems caused by burning coal Describe the adverse effects (include chemical reactions) of common pollutants on buildings, health, vegetation, ozone layer, etc. Describe methods controlling pollution such as acid rain, toxic waste, etc. State uses of catalytic converters and unleaded petrol in reducing pollution from car exhausts State the role of recycling in conservation of natural resources and reducing the problem of pollution Describe some of the problems caused by the chemistry industry Explain the importance of recycling, identify methods of recycling of various substances (e.g. paper, metals, glass, water) Find out advantages of using recyclable materials Be aware of the chemical processes taking place when fuels are burned State that fuel releases energy when it is burnt State that fuel burning is an exothermic reactions State that energy released was stored in the bonds of the fuel molecules ©Word Crackers Tutorials 49 State that carbon monoxide is produced when carbon-containing fuels burn in a limited supply of oxygen Describe how charcoal can be made from wood Explain the need to find alternative sources of energy Explain energy conservation methods used in the home Discuss the advantages and disadvantages of various energy sources Describe one use of plants in producing a fuel Describe the use of plant and animal waste in producing fuel Relate the structure of silicon to its ability to trap solar energy ©Word Crackers Tutorials 50 EXAMINATION QUESTIONS 1. (a) Temporary hardness of water is caused by the presence of calcium hydrogen carbonate, Ca(HCO3)2. i. How can temporary hard water be softened, without adding a chemical? …………………………………………………………………………… [1] ii. When a sample of temporary hard water is softened, a solid is formed. Name this solid. …………………………………………………………………………… [2] (b) Permanent hardness of water can be caused by the presence of calcium sulphate and magnesium sulphate. (i) Complete the equation which shows how hard water is made soft by washing soda, Na2CO3. Include the state symbols. Na2CO3 ( ) + CaSO4( ) → ……………… ( ) + …………… ( ) (ii) Use the state symbols to explain that the hard water has been softened by the washing soda. ………………………………………………………………………………… ………………………………………………………………………………… ……………………………………………………………………………… [3] BGCSE 2000 2. Pollutants gases such as carbon monoxide and oxides of nitrogen are produced by a car engine are emitted through the exhaust pipe. (a) Describe how oxides of nitrogen are formed in car engines. ……………………………………………………………………………………… ………………………………………………………………………………… [2] (b) Explain how carbon monoxide affects human health. ……………………………………………………………………………………… ………………………………………………………………………………….. [2] (c) What is the purpose of catalytic converters in car exhausts? ………………………………………………………………………………….. [1] (d) Suggest why catalytic converters contain a network of fine holes. ……………………………………………………………………………………… ………………………………………………………………………….………. [2] (e) Carbon dioxide, nitrogen and oxygen are all present in clean air. i. State the proportion of oxygen in clean air. ………………………………………………………………………….. [1] ii. Name the process used to separate oxygen and nitrogen from air. ………………………………………………………………………….. [1] BEC 2012 ©Word Crackers Tutorials 51 ABOUT WORD CRACKERS TUTORIALS MISSION We exist to help students excel in all subject areas by providing them with effective learning techniques and principles that will empower them with life transforming skills and attitudes that value education. VISION Our vision is to equip students with the necessary tools and measures for academic excellence as well as developing them into being responsible citizens who are industrially oriented for the future. BACKGROUND INFORMATION Word Crackers Tutorials was established in February 2011 as a program giving back to the community. The aim was to make tuition affordable and therefore accessible to everyone. The success that was achieved in the first year challenged the pioneers of the program to transform it into a business and it was legally registered on the 4th day of April 2014. SERVICES Word Crackers Tutorials offers tuition for BGCSE, IGCSE, JCE, PSLE, AAT, Bachelor of Science, Statistics, ICT, Accounting, Management, Marketing and Economics. LOCATION We are located at plot no. 10411, White City, Gaborone opposite Standard Chartered Bank along old Lobatse road. Another branch is located at KB Mall (inside KB Medical Clinic), Gaborone Bus rank. CONTACTS Tel: 3104726 Cell: 71705458 Email: wordcrackers@gmail.com Facebook: You can like our page Word Crackers-Botswana or join our group Stars of Word Crackers Tutorials. ©Word Crackers Tutorials 52 OUR RESULTS SPEAK FOR US 2011 WORD CRACKERS TUTORIALS TOP THREE STUDENTS NAME ENG MAT BIO CHE PHY D/A BEST 6 PNTS 1. Lethabo Kgakatsi - - - A * - 2*, 2As, 2Bs 46 2. Khumo Mazunga - B A A A - 4As, 3Bs 46 3. Naomi Toise - C - - - AA 3As, 2Bs, 1C 44 2012 WORD CRACKERS TUTORIALS TOP THREE STUDENTS NAME ENG MAT BIO CHE PHY D/A 1. Genious Nkwe - B B 2. Bontle Bornwell - B A A A - 3. Noleen Moepeng - B - - - AA A A - BEST 6 PNTS 4As, 2Bs 46 4As, 3Bs 44 2As, 3Bs, 1C 43 2013 WORD CRACKERS TUTORIALS TOP THREE STUDENTS NAME ENG MAT BIO CHE PHY SDA 1. Kabo Majwabe A A A A A 2. Maitseo Setlhoka C A - - 3. Same Baeti B B - ©Word Crackers Tutorials - BEST 6 PNTS - 1*, 7As 48 - AA 3As, 3Bs 45 - ** 2*s, 3Bs, 1C 43