Principles of Chemistry 30/11/2019 30/11/2019 Principles of Chemistry EdExcel 9-1 iGCSE Chemistry topic 1 W Richards Education Using PowerPoint

30/11/2019 A – States of Matter

Particle theory revision Particle theory is all about explaining the properties of solids, liquids and gases by looking at what the particles do. SOLIDS In a solid the particles ______ around a _____ position. There is a ______ force of attraction between each particle and they are very _____ together Words – strong, close, vibrate, fixed

Words – fixed, collide, quickly, close, squashed, solids LIQUIDS GASES In a liquid the particles are _____ together but can move in any direction. They won’t keep a _____ shape like _____ do. In a gas the particles are very far apart and move _____ in all directions. They often ______ with each other and because they are far apart they can be easily _______. Particles in a gas have the most energy. Words – fixed, collide, quickly, close, squashed, solids (zoomed out)

Q. What are these changes of state called? 30/11/2019 Q. What are these changes of state called? How do you turn a solid into a liquid and then a liquid into a gas? What about the reverse? 1 2 4 3 5

Q. Does the mass of substance change during these changes of state? Changes of Mass 30/11/2019 Q. Does the mass of substance change during these changes of state? What’s happened here? 1 2 4 3 5

Gas Diffusion 30/11/2019 Diffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger… The “scent particles” from this hamburger are in high concentration here: Eventually they will “diffuse” out into this area of low concentration:

Another example of diffusion 30/11/2019 Here’s a lump of potassium permanganate in water. What will eventually happen to it? What if the temperature of the liquid was raised?

Dissolving things – some definitions 30/11/2019 If a substance CAN be dissolved it is called __________ If a substance CANNOT be dissolved it is called _________ Words – soluble, solute, solvent, solution, insoluble

Saturated solutions What happens when you put too much solute in? 30/11/2019 What happens when you put too much solute in? Clearly, there is only so much solute a solution can take… A mixture that cannot take any more solute is called a “saturated solution”

Solubility words Solute 30/11/2019 Something that CAN dissolve is described as being… How much of something that can be dissolved is called… Something that CANNOT be dissolved is described as being… A solution that CAN’T dissolve anything else is… The solid that will be dissolved is the… The mixture of solute and solvent is called the… The liquid that the solute will be dissolved into is the… Solute Solution Solvent Soluble Insoluble Saturated Solubility

Solubility (Chem only) 30/11/2019 “Solubility” means “how much can be dissolved” and is measured in grams per 100g of solvent. Solubility usually increases with temperature: Solubility g/100g 10 20 30 40 50 60 Temperature/0C Salt Potassium chloride

Example Solubility Question (Chem only) 30/11/2019 Q. If a saturated solution of salt was cooled from 50OC to 20OC, how much salt would crystallise? 40g Solubility g/100g 10 20 30 40 50 60 Temperature/0C Salt Potassium chloride

B – Elements, Compounds and Mixtures 30/11/2019 B – Elements, Compounds and Mixtures

Elements 30/11/2019 If a solid, liquid or gas is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron: These atoms are ALL iron – there’s nothing else in here

Sodium chloride (salt) Compounds 30/11/2019 Sodium chloride (salt) Methane Compounds are formed when two or more elements are chemically combined. Some examples: Glucose

Some simple compounds… 30/11/2019 Methane, CH4 Carbon dioxide, CO2 Water, H2O Key Hydrogen Oxygen Carbon sulfur sulfuric acid, H2SO4 Ethyne, C2H2

Element, compound or mixture? 30/11/2019 Hydrogen Element Hydrochloric acid Compound Air Mixture

Element, mixture or compound? 30/11/2019 Salty water Hydrogen Hydrochloric acid Air Diamond Sodium chloride (salt)

Heating ice 150 Temp/OC Water boils at 100OC 100 50 Time/s -50 30/11/2019 Temp/OC 150 100 50 -50 Water boils at 100OC Ice melts at 0OC Time/s

Boiling Points of Mixtures 30/11/2019 Pure elements and compounds boil at specific temperatures (e.g pure water boils at 100OC). However, what happens when you have a mixture? % of ethanol % of water Boiling Point (OC) 100 78 80 20 82 60 40 90 94 98 Some questions: What temperature does pure ethanol boil at? What effect does adding ethanol have to the boiling point? What would be the boiling point of a 50/50 mix?

Separating Mixtures 1 - Distillation 30/11/2019 This apparatus can be used to separate water and ethanol because they have different _____ ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The water remains in the round flask, as long as the _______ does not exceed water’s boiling point. This method can be used to separate any liquids with different boiling points such as the fractional distillation of ____ ___. Words – temperature, boiling points, ethanol, beaker, liquid, crude oil

Separating Mixtures 2 - Fractional distillation 30/11/2019 30/11/2019 Separating Mixtures 2 - Fractional distillation Crude oil can be separated by fractional distillation as each liquid making up crude oil has a different boiling point: Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom

Separating Mixtures 3 and 4 30/11/2019 Filtration Crystallisation

Evaporation and crystallisation using rock salt 30/11/2019 Evaporation and crystallisation using rock salt In this practical we tried to separate rock salt – a mixture of ____ and sand. To do this we followed four steps: We ground the rock salt using a ______ and mortar, We dissolved the mixture, We _________ it, We evaporated the remains to form _______. The sand didn’t _________, so we were able to filter it out. The salt did dissolve, so we had to ________ the remains to get the salt back. Conclusion: Filtration can be used to remove something that doesn’t dissolve and evaporation can be used to separate something that does dissolve. Words – filtered, salt, pestle, crystals, evaporate, dissolve

Separating Mixtures 5 - Chromatography 30/11/2019 Chromatography can be used to separate a mixture of different inks. Some example questions… R G B X 1 2 3 Z 1) Ink X contains two different colours. What are they? 2) Which ink is ink Z made out of?

Rf value 30/11/2019 The Rf value is a way of measuring how far a substance has moved: This line marks the distance travelled by the solvent R G B Rf value = Distance travelled by substance Distance travelled by solvent

Example questions Calculate the Rf values of the following: 10cm 8cm 30/11/2019 Calculate the Rf values of the following: R G B 10cm 2cm 8cm 5cm

Separating mixtures summary 30/11/2019 A mixture containing something that DOES dissolve can be separated using __________ A mixture of liquids with different boiling points can be separated using _________ A mixture of different inks can be separated using _______ A mixture containing something that DOES NOT dissolve can be separated using _________ Words: Distillation, chromatography, evaporation, filtration

C – Atomic Structure 30/11/2019

Molecules 30/11/2019 An individual particle or group of particles is called a “molecule”. Some examples… Some molecules of hydrochloric acid Molecules of water and some dissolved impurities One molecule of methane

The structure of the atom 30/11/2019 Hello there. In 1808 I did some experiments that helped us to understand what atoms, the building blocks of the universe, actually look like: Dalton ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron NEUTRON – neutral, same mass as proton

The structure of the atom 30/11/2019 30/11/2019 Particle Relative Mass Relative Charge Proton 1 +1 Neutron Electron 1/2000 (i.e. 0) -1 MASS NUMBER = number of protons + number of neutrons He 2 4 SYMBOL ATOMIC NUMBER = number of protons. All atoms of a particular element must have the same number of protons.

Mass and atomic number 1 11 16 H B O 1 5 8 23 35 238 Na Cl U 11 17 92 30/11/2019 30/11/2019 How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35 238 Na Cl U 11 17 92

Strange atomic masses 35.5 Cl 17 30/11/2019 When you look at a periodic table sometimes the atomic mass is not a whole number. Consider chlorine, for example: How can an atom have a decimal for its mass? Cl 17 35.5 This is because out of every four naturally occurring chlorine atoms, 3 have a mass of 35 and 1 has a mass of 37 so the average atomic mass is: (3 x 35 + 1 x 37) / 4 = 35.5 Q. Magnesium is often found as 24Mg or 26Mg. If 79% of magnesium is 24Mg what is the average atomic mass? (79 x 24 + 21 x 26) / 100 = 24.4

D – The Periodic Table 30/11/2019

Periodic Table Introduction 30/11/2019 How would you arrange these elements into groups?

Horizontal rows are called PERIODS The Periodic table 30/11/2019 Mendeleev The periodic table arranges all the 100 or so elements in groups according to their properties and in order of their atomic number. Vertical columns are called GROUPS Horizontal rows are called PERIODS

Electron structure 39 K 19 Consider an atom of Potassium: 30/11/2019 Consider an atom of Potassium: Nucleus K 19 39 Potassium has 19 electrons. These electrons occupy specific energy levels “shells”… The inner shell has __ electrons The next shell has __ electrons The next shell has the remaining __ electron Electron structure = 2,8,8,1

Electron structure 14 24 40 N Mg Ca 7 12 20 30/11/2019 Draw the electronic structure of the following atoms: 14 24 40 N Mg Ca 7 12 20 Nucleus Nucleus Nucleus Electron structure = 2,5 Electron structure = 2,8,2 Electron structure = 2,8,8,2

The Periodic Table 30/11/2019 Fact 1: Elements in the periodic table are arranged in order of proton number: H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg E.g. Lithium has 3 protons while Beryllium has 4

The Periodic Table 30/11/2019 Fact 2: Elements in the same group have the same number of electrons in the outer shell (this corresponds to their group number) H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg These elements have __ electrons in their outer shells These elements have __ electrons in their outer shell E.g. all group 1 metals have __ electron in their outer shell

The Periodic Table 30/11/2019 Fact 3: As you move down through the periods an extra electron shell is added: E.g. Lithium has 3 electron in the configuration 2,1 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg Sodium has 11 electrons in the configuration 2,8,1 Potassium has 19 electrons in the configuration __,__,__,__

Fact 4: Most of the elements are metals: The Periodic Table 30/11/2019 Fact 4: Most of the elements are metals: These elements are metals – they conduct electricity and form “basic oxides” H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg This line divides metals from non-metals These elements are non-metals – they don’t conduct electricity and form “acidic oxides”

The Periodic Table 30/11/2019 Fact 5: (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the periodic table in the first place. This is called PERIODICITY. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg E.g. consider the group 1 metals. They all: Are soft Can be easily cut with a knife React with water

Group 0 – The Noble gases He Ne Ar Kr Xe Rn Questions: 30/11/2019 He Ne Ar Kr Xe Rn Questions: How many electrons do these elements have in their outer shell? How does this affect their reactivity?

E – Chemical Formulae, Equations and Calculations 30/11/2019 E – Chemical Formulae, Equations and Calculations

Naming compounds 30/11/2019 Rule 1 – If two identical elements combine then the name doesn’t change This happens with the following elements: H2 N2 O2 F2 Cl2 Br2 Hydrogen Nitrogen Oxygen Fluorine Chlorine Bromine These elements always go around in pairs. For example, hydrogen looks like this:

Rule 2 – When two elements join the end is usually _______ide. Naming compounds 30/11/2019 Rule 2 – When two elements join the end is usually _______ide. e.g. Magnesium + oxygen magnesium oxide Sodium + chlorine Magnesium + fluorine Lithium + iodine Chlorine + copper Oxygen + iron Sodium chloride Magnesium fluoride Lithium iodide Copper chloride Iron oxide

e.g. Sodium + hydrogen + oxygen Sodium hydroxide Naming compounds 30/11/2019 Rule 3 – When three or more elements combine and two of them are hydrogen and oxygen the name ends with hydroxide e.g. Sodium + hydrogen + oxygen Sodium hydroxide Potassium + hydrogen + oxygen Lithium + hydrogen + oxygen Calcium + hydrogen + oxygen Mg(OH)2 Potassium hydroxide Lithium hydroxide Calcium hydroxide Magnesium hydroxide

e.g. Copper + sulfur + oxygen Copper sulfate Naming compounds 30/11/2019 Rule 4 – When three or more elements combine and one of them is oxygen the ending is _____ate e.g. Copper + sulfur + oxygen Copper sulfate Calcium + carbon + oxygen Potassium + carbon + oxygen Calcium + sulfur + oxygen Magnesium + chlorine + oxygen Calcium + oxygen + nitrogen Calcium carbonate Potassium carbonate Calcium sulfate Magnesium chlorate Calcium nitrate

Sodium + water sodium hydroxide + hydrogen Balancing equations 30/11/2019 Consider the following reaction: Sodium + water sodium hydroxide + hydrogen Na O H O H Na + H + This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”)

Balancing equations We need to balance the equation: 30/11/2019 We need to balance the equation: Sodium + water sodium hydroxide + hydrogen Na O H O H Na O H Na O H + H + Na Now the equation is balanced, and we can write it as: 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

State Symbols Recall this reaction: 30/11/2019 Recall this reaction: Sodium + water sodium hydroxide + hydrogen Na O H + 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g) s = solid l = liquid aq = aqueous solution g = gas

Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 30/11/2019 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 Ca + H2O NaOH + H2SO4 CH3OH + O2 MgO ZnCl2 + H2 FeCl3 NaCl + H2O CO2 + H2O Ca(OH)2 + H2 Na2SO4 + H2O 2 2 4

Relative formula mass, Mr 30/11/2019 The relative formula mass of a compound is the relative atomic masses of all the elements in the compound added together. Relative atomic mass of O = 16 E.g. water H2O: Relative atomic mass of H = 1 Therefore Mr for water = 16 + (2x1) = 18 Work out Mr for the following compounds: HCl NaOH MgCl2 H2SO4 K2CO3 H=1, Cl=35 so Mr = 36 Na=23, O=16, H=1 so Mr = 40 Mg=24, Cl=35 so Mr = 24+(2x35) = 94 H=1, S=32, O=16 so Mr = (2x1)+32+(4x16) = 98 K=39, C=12, O=16 so Mr = (2x39)+12+(3x16) = 138

Recap Questions 30/11/2019 Here are carbon and oxygen on the Periodic Table and a picture of carbon dioxide: Carbon dioxide, CO2 C 6 12 O 8 16 What is the atomic mass of carbon? What is the atomic mass of oxygen? What is the molecular mass of carbon dioxide?

A “Mole” in numbers Definition: 30/11/2019 Definition: A mole of a substance is the relative formula mass of that substance in grams, For example, 12g of carbon would be 1 mole of carbon... ...and 44g of carbon dioxide (CO2) would be 1 mole etc... Q. How many moles are the following? 23g of sodium 48g of magnesium 36g of carbon 28g of iron 1 mol 2 mol 3 mol 0.5 mol

Molar Calculations No. of moles = Mass (g) Molar mass (g/mol) N = m M 30/11/2019 No. of moles = Mass (g) Molar mass (g/mol) N = m M Some example questions: Calculate the mass of 4 mol of lithium Calculate the mass of 2 mol of sodium Calculate the number of moles in 36g of carbon Calculate the number of moles in 88g of carbon dioxide Calculate the number of moles in 27g of water 28g 46g 3 mol 2 mol 1.5 mol

Calculating the mass of a product 30/11/2019 E.g. what mass of magnesium oxide is produced when 60g of magnesium is burned in air? IGNORE the oxygen in step 2 – the question doesn’t ask for it Step 1: READ the equation: 2Mg + O2 2MgO Step 2: WORK OUT the relative formula masses (Mr): 2Mg = 2 x 24 = 48 2MgO = 2 x (24+16) = 80 Step 3: LEARN and APPLY the following 3 points: 48g of Mg makes 80g of MgO 1g of Mg makes 80/48 = 1.66g of MgO 60g of Mg makes 1.66 x 60 = 100g of MgO

Calculating the mass of a product using moles 30/11/2019 Calculating the mass of a product using moles Let’s try this question again but using moles: Step 1: READ the equation: 2Mg + O2 2MgO “2 moles of magnesium + 1 mole of oxygen forms 2 moles of magnesium oxide” Step 2: WORK OUT the relative formula masses (Mr) of MgO: 2MgO = 2 x (24+16) = 80 Step 3: Apply these steps: 60g of Mg is equal to 1.25 moles (60/48) Therefore we will make 1.25 moles of magnesium oxide Therefore we make 100g of MgO (1.25 moles)

Mr: 2Al2O3 = 2x((2x27)+(3x16)) = 204 4Al = 4x27 = 108 When water is electrolysed it breaks down into hydrogen and oxygen: 2H2O 2H2 + O2 What mass of hydrogen is produced by the electrolysis of 6g of water? 30/11/2019 Work out Mr: 2H2O = 2 x ((2x1)+16) = 36 2H2 = 2x2 = 4 36g of water produces 4g of hydrogen So 1g of water produces 4/36 = 0.11g of hydrogen 6g of water will produce (4/36) x 6 = 0.66g of hydrogen 2) What mass of calcium oxide is produced when 10g of calcium burns? 2Ca + O2 2CaO Mr: 2Ca = 2x40 = 80 2CaO = 2 x (40+16) = 112 80g produces 112g so 10g produces (112/80) x 10 = 14g of CaO 3) What mass of aluminium is produced from 100g of aluminium oxide? 2Al2O3 4Al + 3O2 Mr: 2Al2O3 = 2x((2x27)+(3x16)) = 204 4Al = 4x27 = 108 204g produces 108g so 100g produces (108/204) x 100 = 52.9g of Al2O3

So mass of product = (4/36) x 6g = 0.66g of hydrogen Another method 30/11/2019 Try using this equation: Mass of product IN GRAMMES Mass of reactant IN GRAMMES Mr of product Mr of reactant Q. When water is electrolysed it breaks down into hydrogen and oxygen: 2H2O 2H2 + O2 What mass of hydrogen is produced by the electrolysis of 6g of water? Mass of product IN GRAMMES 4 6g 36 So mass of product = (4/36) x 6g = 0.66g of hydrogen

Using Moles to balance equations 30/11/2019 Example question: 130g of zinc reacts with 146g of hydrochloric acid (HCl) to form 272g of zinc chloride (ZnCl2) and some hydrogen (H2). Answer the following: How much hydrogen was produced? How many moles of each substance were reacted/produced? Write a balanced chemical equation for this reaction. 4g 1 of Zn, 2 of HCl, 1 of ZnCl2, 1 of H2 Zn + 2HCl ZnCl2 + H2

Recap questions Key Carbon dioxide, CO2 Oxygen, O2 Methane, CH4 30/11/2019 Carbon dioxide, CO2 Oxygen, O2 Methane, CH4 Water, H2O Key Hydrogen Oxygen Carbon sulfur What are the molecular masses of these four compounds? How many grams of each compound would you have if you had one mole of each one? Which mole is the heaviest?

Percentage Yield Percentage yield = Actual yield Predicted yield 30/11/2019 Percentage yield = Actual yield Predicted yield X 100% Some example questions: The predicted yield of an experiment to make salt was 10g. If 7g was made what is the percentage yield? Dave is trying to make water. If he predicts to make 15g but only makes 2g what is the percentage yield? Sarah performs an experiment and has a percentage yield of 33%. If she made 50g what was she predicted to make? 70% 13% 150g

A classic exam question: Empirical formulae 30/11/2019 Empirical formulae is simply a way of showing how many atoms are in a molecule (like a chemical formula). For example, CaO, CaCO3, H20 and KMnO4 are all empirical formulae. Here’s how to work them out: A classic exam question: Find the simplest formula of 2.24g of iron reacting with 0.96g of oxygen. Step 1: Divide both masses by the relative atomic mass: For iron 2.24/56 = 0.04 For oxygen 0.96/16 = 0.06 Step 2: Write this as a ratio and simplify: 0.04:0.06 is equivalent to 2:3 Step 3: Write the formula: 2 iron atoms for 3 oxygen atoms means the formula is Fe2O3

Example questions 30/11/2019 Find the empirical formula of magnesium oxide which contains 48g of magnesium and 32g of oxygen. Find the empirical formula of a compound that contains 42g of nitrogen and 9g of hydrogen. Find the empirical formula of a compound containing 20g of calcium, 6g of carbon and 24g of oxygen. MgO NH3 CaCO3

Empirical Formulae vs Molecular Formulae 30/11/2019 Q. What’s the difference between an empirical formula and a molecular formula? Let’s answer this using another question: What is the empirical formula of a compound containing 24g of carbon and 4g of hydrogen? CH2 is the empirical formula. The actual molecule could be C2H4, C3H6 etc Step 1: Divide both masses by the relative atomic mass: Carbon: 24/12 = 2 Hydrogen: 4/1 = 4 Step 2: Write this as a ratio and simplify: 2:4 is equivalent to 1:2 Step 3: Write the formula: 1 carbon atom for 2 hydrogen atoms means the formula is CH2 The molecular formula tells you exactly how many atoms of each element you have whereas the empirical formula simply tells you the ratio.

Determining Empirical Formulae 30/11/2019 Q. How could you use this experiment to deduce the empirical formula of magnesium oxide?

A note about volume… 30/11/2019 The two most commonly used units of volume in chemistry are the cm3 and the dm3: 1dm3 (= 1000cm3) 1cm3 Convert 1250cm3 into dm3 Convert 1cm3 into dm3 Convert 0.056dm3 into cm3 Convert 1.28dm3 into cm3

Concentration 30/11/2019 Concentration means “how much of a chemical there is in a fixed volume” and can be measured in g/dm3 or mol/dm3. A solution of low concentration (“dilute”) A solution of high concentration (“strong”)

Questions on Concentration 30/11/2019 To calculate the concentration of a substance you could use one of these formulae: Conc. = Mass of substance (g) Volume of solvent (dm3) Conc. = Amount of solute (mol) Calculate, with units, the concentration of the following: A solution of 10g salt in 1dm3 of water 2mol of hydrochloric acid in 500cm3 of water 10kg of salt in 200dm3 of water 0.5mol of sodium hydroxide in 100cm3 of water

Converting concentrations 30/11/2019 To convert g/dm3 into mol/dm3 you can use the following formula: Concentration = Concentration (g/dm3) (mol/dm3) Molar mass Convert the following: 0.5mol/dm3 of sodium hydroxide into g/dm3. 2mol/dm3 of HCl into g/dm3. 20g/dm3 of NaCl into mol/dm3. 500g/dm3 of CaCl2 into mol/dm3.

Calculating Volumes of Gases (Chem only) 30/11/2019 An important fact: 1 mole of a gas at room temperature (20OC) and pressure (1 atm) occupies a volume of 24dm3. Therefore number of moles = volume of gas (in dm3) 24dm3 What is the volume of 2 moles of oxygen? What is the volume of 0.25 moles of carbon dioxide? How many moles would be in 8dm3 of nitrogen? How much volume would 80g of argon occupy? A balloon contains 12dm3 of carbon dioxide. What is the mass of this much CO2? 48dm3 6dm3 1/3 mol 48dm3 22g

Practical – determining a formula using combustion 30/11/2019 Here’s a classic experiment where magnesium is burned in a crucible: Mass of magnesium and crucible after burning = 78.56g Mass of magnesium and crucible before burning = 78.25g 2Mg + O2 2MgO How can we use this experiment to determine the formula of magnesium oxide?

F – Ionic Bonding 30/11/2019

Introduction to Bonding 30/11/2019 Cl Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell Cl I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me?

Ionic Bonding introduced 30/11/2019 Cl Here comes a friend, Sophie Sodium Na Hey Johnny. I’m in Group 1 so I have one electron in my outer shell. I don’t like only having one electron there so I’m quite happy to get rid of it. Do you want it? Okay - + Cl Na Now we’ve both got full outer shells and we’ve both gained a charge which attracts us together. We’ve formed an IONIC bond.

This is called an ion (in this case, a positive hydrogen ion. Ions 30/11/2019 An ion is formed when an atom gains or loses electrons and becomes charged: + - The electron is negatively charged The proton is positively charged + + If we “take away” the electron we’re left with just a positive charge: This is called an ion (in this case, a positive hydrogen ion.

The Periodic Table 30/11/2019 30/11/2019 Looking at their position in the Periodic Table and understanding their electron structure, we can predict the charge of different ions. For example, group 1 elements all want to lose one electron so they will all form ions with a charge of +1 What type of ion (and its charge) will elements from groups 2, 3, 5, 6 and 7 form? H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg

Balancing ions Learn these common ions: Silver – Ag+ Copper – Cu2+ 30/11/2019 Learn these common ions: Silver – Ag+ Copper – Cu2+ Iron – Fe2+ or Fe3+ Lead – Pb2+ Zinc – Zn2+ Hydroxide – OH- Ammonium – NH4+ Carbonate – CO32- sulfate – SO42- Nitrate – NO3- Determine the formula of the following compounds: Sodium chloride Magnesium oxide Magnesium chloride Ammonium chloride Sodium sulfate NaCl MgO MgCl2 NH4Cl Na2SO4 Copper sulfate Copper nitrate Ammonium sulfate Zinc chloride Sodium carbonate CuSO4 Cu(NO3)2 (NH4)2SO4 ZnCl2 Na2CO3

Words – full, transfers, positively, negatively, metals, anion, stable Ionic bonding 30/11/2019 This is where a metal bonds with a non-metal (usually). Instead of sharing the electrons one of the atoms “_____” one or more electrons to the other. For example, consider sodium and chlorine: Na Cl Sodium has 1 electron on its outer shell and chlorine has 7, so if sodium gives its electron to chlorine they both have a ___ outer shell and are ______. Na + A _______ charged sodium ion (cation) A _________ charged chloride ion (______) Cl - Group 1 _______ will always form ions with a charge of +1 when they react with group 7 elements. The group 7 element will always form a negative ion with charge -1. Words – full, transfers, positively, negatively, metals, anion, stable

Dot and Cross diagrams of ionic bonds 30/11/2019 Cl - Magnesium chloride: Cl Mg 2+ Mg + Cl - Cl MgCl2 Calcium oxide: O Ca + 2+ 2- CaO

Giant Ionic Structures 30/11/2019 Cl- Na+ When many positive and negative ions are joined they form a “giant ionic lattice” where each ion is held to the other by strong electrostatic forces of attraction. This is an “ionic bond”: If these ions are strongly held together what affect would this have on the substance’s: Melting point? Boiling point? State (solid, liquid or gas) at room temperature?

Dissolving Ionic Structures 30/11/2019 When an ionic structure like sodium chloride is dissolved it enables the water to conduct electricity as charge is carried by the ions: Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+

G – Covalent Bonding 30/11/2019

Introduction to Bonding Revision 30/11/2019 Cl Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell Cl I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me?

Covalent Bonding 30/11/2019 Cl Here comes another one of my friends, Harry Hydrogen Hey Johnny. I’ve only got one electron but it’s really close to my nucleus so I don’t want to lose it. Fancy sharing? H Cl H Now we’re both really stable. We’ve formed a covalent bond.

Words – covalent, 1, 2, share, full, stable. electrostatic Covalent bonding 30/11/2019 Consider an atom of hydrogen: Notice that hydrogen has just __ electron in its outer shell. A full (inner) shell would have __ electrons, so two hydrogen atoms get together and “_____” their electrons: Now they both have a ____ outer shell and are more _____. The formula for this molecule is H2. When two or more atoms bond and form a molecule by sharing electrons we call it ____________ BONDING. The atoms are held together by _________ attraction. Words – covalent, 1, 2, share, full, stable. electrostatic

Dot and Cross Diagrams for Covalent Molecules 30/11/2019 Water, H2O: H H O

Dot and Cross Diagrams for Covalent Molecules 30/11/2019 Dot and Cross Diagrams for Covalent Molecules Oxygen, O2: O O

Dot and cross diagrams Water, H2O: H O O H H Oxygen, O2: O O O 30/11/2019 Water, H2O: Step 1: Draw the atoms with their outer shell: Step 2: Put the atoms together and check they all have a full outer shell: H O O H H Oxygen, O2: O O O

Dot and cross diagrams Nitrogen, N2: Methane CH4: N C H Ammonia NH3: 30/11/2019 Nitrogen, N2: Methane CH4: H C N Ammonia NH3: Carbon dioxide, CO2: H N O C

Properties of simple molecules 30/11/2019 Recall our model of a simple covalent compound like hydrogen, H2: H Hydrogen has a very low melting point and a very low boiling point. Why? 2) When a substance is heated it is the intermolecular forces that are overcome, NOT the covalent bond in each molecule, which is much stronger! 1) The intermolecular forces are very weak so each one of these H2 molecules doesn’t really care about the others – it’s very easy to pull them apart. Also, the molecules do not carry a charge so covalent compounds usually do not conduct electricity.

Larger Molecules 30/11/2019 Recall this data about group 7. Can you explain why the melting and boiling points get bigger as you go down the group? Element Melting Point (OC) Boiling Point (OC) Flourine -220 -188 Chlorine -101 -34 Bromine -7 59 Iodine 114 184 The intermolecular forces get bigger as the molecules get bigger. This is why melting point and boiling points go up.

Different forms of elements and compounds 30/11/2019 Elements and compounds can form many different structures, including: Cl- Na+ 1) Ionic, like sodium chloride: 2) Giant covalent structures, like graphite: + 3) Metallic, like iron: H C 4) Simple covalent molecules, like methane:

Giant Covalent structures (“lattices”) 30/11/2019 Notice that giant covalent structures have very different properties to individual covalent molecules: 2. Graphite – carbon atoms arranged in a layered structure, with free _______ in between each layer enabling carbon to conduct _________ (like metals) 1. Diamond – a giant covalent structure with a very ____ melting point due to ______ bonds between carbon atoms 3. Silicon dioxide (sand) – a giant covalent structure of silicon and oxygen atoms with strong _____ causing a high ______ point and it’s a good insulator as it has no free electrons O Si Words – melting, high, electrons, bonds, strong, electricity

Using Covalent Structures 30/11/2019 Element/ compound Property Uses Why? Carbon – diamond Very hard Drill tips Extremely strong covalent structure Carbon - graphite Soft Lubricants Layers “slip” off each other Conducts electricity Making electrodes Free electrons to carry charge

Fullerenes 30/11/2019 Carbon can also be used to make structures called “fullerenes” (carbon atoms forming an empty shape). Fullerenes are compounds used for applications such as drug delivery, lubricants, catalysts and nanotubes and they have structures based on carbon atoms forming hexagonal rings: “Buckminster fullerene” – the first fullerene to be discovered in 1960. A “carbon nanotube” – high tensile strength, high electrical conductivity and high thermal conductivity

H – Metallic Bonding (Chem only) 30/11/2019

Delocalised electrons Metals 30/11/2019 Metals are defined as elements that readily lose electrons to form positive ions. The electrons in the highest shells are delocalised and able to move around, causing the ions to be held together by strong electrostatic forces, causing metals to have high melting points. + + + - Delocalised electrons

Understanding thermal and electrical conductivity 30/11/2019 Understanding thermal and electrical conductivity As we’ve said before, metals have delocalised electrons that enable them to conduct electricity and heat very well: Electrons Ions The delocalised electrons can move around the metal ions. This is how metals conduct heat and electricity. Metals are also “malleable” – this means that they can be hammered into thin sheets without breaking, due to the electrostatic attractions within the structure.

I – Electrolysis (Chem only) 30/11/2019

Recap on covalent compounds 30/11/2019 Here are some covalent compounds we have come across. Q. Do they conduct electricity? Explain your answer. O Si H C

Dissolving Ionic Structures 30/11/2019 When an ionic structure like sodium chloride is dissolved it enables the water to conduct electricity as charge is carried by the ions: Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+

Electrolysis of Copper Sulfate 30/11/2019 Electrolyse copper sulfate and record your observations. What is happening at each electrode? Positive electrode (“anode”) ++++ ---- Negative electrode (“Cathode”) Cu2+ SO42- Electrolyte solution containing copper ions (cations) and sulfate ions (anions) SO42- Cu2+ SO42- Cu2+

Electrolysis 30/11/2019 During electrolysis a substance is broken down using electricity: = chloride ion = copper ion When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!!

The Reactivity Series Increasing reactivity Note where hydrogen is 30/11/2019 Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold Increasing reactivity Note where hydrogen is

Electrolysis of Aqueous Solutions 30/11/2019 The ions discharged by electrolysis depend on the relative reactivity of the elements involved: ++++ ---- At the positive electrode (anode), oxygen is produced UNLESS the solution contains halide ions, in which case a halogen is produced. At the negative electrode (cathode), hydrogen is produced IF the metal is more reactive than hydrogen.

Products from electrolysis 30/11/2019 Given these two rules, complete the following table: Electrolyte Product at cathode Product at anode Copper chloride solution Copper sulfate solution Sodium sulfate solution Molten lead bromide Copper Chlorine Copper Oxygen Hydrogen Oxygen Lead Bromine

Electrolysis half equations 30/11/2019 We need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride): At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is: Cu2+ + e- Cu 2 At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is: Cl- - e- Cl2 2 2

Redox reactions “Redox” reactions happen during electrolysis: 30/11/2019 “Redox” reactions happen during electrolysis: At the positive electrode (anode) the negative ions LOSE electrons to become neutral – this is OXIDATION At the negative electrode (cathode) the positive ions GAIN electrons to become neutral – this is REDUCTION These two processes are called REDOX REACTIONS OILRIG – Oxidation Is Loss of electrons Reduction Is Gain of electrons

Electrolysis of molten sodium chloride 30/11/2019 If you electrolyse molten sodium chloride instead of its solution you get different products: Positive electrode (“anode”) ++++ ---- Negative electrode (“Cathode”) Na+ Cl- Na+ Cl- Na+ Cl- Write half equations for these reactions and state where oxidation and reduction occur