Preliminary Chemistry Notes

8.2 The Chemical Earth

Part 1: The living and non-living components of the Earth contain mixtures

1.1: construct word and balanced formulae equations of chemical reactions as they are encountered

Example (photosynthesis): carbon dioxide + water –sunlight oxygen + glucose

6CO2 + 12H2O → 6O2 + C6H12O6 + 6H2O

1.2: identify the difference between elements compounds and mixtures in terms of particle theory

Elements – pure substance that contains only one type of particle. E.g oxygen, iron, phosphorus

Compounds – pure substance – composed of 2 or more elements chemically combined in fixed proportions. E.g water (H2O), carbon dioxide (CO2)

Mixtures – contains different particles not chemically combined, either in equal or uneven ratios. E.g air, sea water

1.3: identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds

Atmosphere: oxygen, nitrogen, argon, carbon dioxide, methane, waterHydrosphere: chlorine, sodium, magnesium, potassium, calcium, sulphur, bromine, carbon dioxide, waterLithosphere: sodium, calcium, aluminium, quartz, biotite, kaoliniteBiosphere: carbon, phosphorus, oxygen, hydrogen, nitrogen, carbon dioxide, water

1.4: identify and describe procedures that can be used to separate naturally occurring mixtures of:- solids of different sizes- solids and liquids- dissolved solids in liquids- liquids- gases

Sedimentation: Process in which solids settle to the bottom of a container

Sieving: Separating solid particles according to particle size by passing them through a perforated barrier

Distillation: Process of separating the liquid component of a solution by boiling the solution and condensing the resulting vapour back to a liquid

Decantation: Process of carefully pouring off the liquid and leaving the solid undisturbed at the bottom of the container

Filtration: Process of separating undissolved solid from a liquid or gas by passing the mixture through a filter

Magnetic Separation: Process of passing a mixture through a magnetic field to separate the magnetic and non-magnetic components

Evaporation: Process of separating a dissolved solid from a solution by vaporising the liquid

Crystallisation: Process of forming crystals form a solution

1.5: assess separation techniques for their suitability in separating examples of earth materials, identifying the differences in properties which enable these separations

Separation technique Earth materials/ mixtures separated by this technique

Properties which enable the solution

Filtration Solids from petrolPurification of water supply

Insoluble solids and a liquid

Evaporation Salt from seawater Substances with different volatilities

Sedimentation Water purification Insoluble solid particles and a liquid or air (solid must be more dense than the filtrate)

Sieving Sort foodstuffs Mining - separate mineral particles Bank - separate coins

Two or more different sizes of solids

Centrifugation Plasma from bloodCream from milk

Substances that differ in density

Fractional distillation Crude oil into petrol Liquids with different boiling points

Chromatography Separate pigments in plant matter

Small quantities of each component in the mixtureComponents cling to surface of an inert substance with different strengths

Magnetic Separating components of mineral sands

Two solids with one being magnetic and the other not

1.6: describe situations in which gravimetric analysis supplies useful data for chemists and other scientists

Gravimetric analysis – analysis by weight or by mass – determining quantities (masses) of substances present in a sample. Gravimetric analysis is useful to:

- Determine the composition of soil in a particular location to see if it suitable for growing to a certain crop

- To determine the amounts of particular substances present in water or air to decide how polluted the samples are

- To decide whether a particular commercial mixture being sold has the same percentage composition as a similar mixture being marketed by a rival company

1.7: apply systematic naming of inorganic compounds as they are introduced in the laboratory

Ionic compounds: Cation named first, then the anion. Cation name stays the same. If the anion is monatomic, then change the ending to -ide. If it is a polyatomic ion then use the name of the polyatomic ion.

1 Mono 6 Hexa2 Di 7 Hepta3 Tri 8 Octa4 Tetra 9 Nona5 Penta 10 Deca

Covalent compounds: Use mono, di, tri, etc. before element name to indicate number of atoms. Do not use mono for the first element.

1.8: identify IUPAC names for carbon compounds as they are encountered

Alkanes: ends with -ane, general formula CnH2n+2

Alkenes: ends with -ene, general formula CnH2n Alkynes: ends with -yne, general formula CnH2n-2

1 Meth 6 Hex2 Eth 7 Hept3 But 8 Oct4 Prop 9 Non5 Pent 10 Dec

1.a: gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the Preliminary course

Acid + base → salt + water Acid + metal carbonate → salt + water + carbon dioxide Acid + metal → salt + hydrogen Metal + oxygen → metal oxide Metal + water (liquid) → metal hydroxide + hydrogen (for metals in Group I, and calcium) Metal + water (steam) → metal oxide + hydrogen (for less reactive metals)

1.b: identify data sources, plan, choose equipment and perform a first-hand investigation to separate the components of a naturally occurring or appropriate mixture such as sand, salt and water

Refer to prac in notes.

1.c: gather first-hand information by carrying out a gravimetric analysis of a mixture to estimate its percentage composition

Refer to prac in notes.

1.d: identify data sources, gather, process and analyse information from secondary sources to identify the industrial separation processes used on a mixture obtained from the biosphere, lithosphere or atmosphere and use the evidence available to:- identify the properties of the mixture used in its separation- identify the products of separation and their uses- discuss issues associated with wastes from the processes used

Define ‘crude oil’

Crude oil is the term for "unprocessed" oil, the stuff that comes out of the ground. It is also known as petroleum. Crude oil is a fossil fuel, meaning that it was made naturally from decaying plants and animals living in ancient seas millions of years ago -- most places you can find crude oil were once sea beds. Crude oils vary in colour, from clear to tar-black, and in viscosity, from water to almost solid.

Describe how ‘fractional distillation’ works

The various components of crude oil have different sizes, weights and boiling temperatures; so, the first step is to separate these components. Because they have different boiling temperatures, they can be separated easily by a process called fractional distillation. The steps of fractional distillation are as follows:

You heat the mixture of two or more substances (liquids) with different boiling points to a high temperature. Heating is usually done with high pressure steam to temperatures of about 1112 degrees Fahrenheit / 600 degrees Celsius.

The mixture boils, forming vapour (gases); most substances go into the vapour phase.

The vapour enters the bottom of a long column (fractional distillation column) that is filled with trays or plates. The trays have many holes or bubble caps (like a loosened cap on a soda bottle) in them to allow the vapour to pass through. They increase the contact time between the vapour and the liquids in the column and help to collect liquids that form at various heights in the column. There is a temperature difference across the column (hot at the bottom, cool at the top).

The vapour rises in the column.

As the vapour rises through the trays in the column, it cools.

When a substance in the vapour reaches a height where the temperature of the column is equal to that substance's boiling point, it will condense to form a liquid. (The substance with the lowest boiling point will condense at the highest point in the column; substances with higher boiling points will condense lower in the column.).

The trays collect the various liquid fractions.

The collected liquid fractions may pass to condensers, which cool them further, and then go to storage tanks, or they may go to other areas for further chemical processing

Fractional distillation is useful for separating a mixture of substances with narrow differences in boiling points, and is the most important step in the refining process.  

Top: The oil refining process starts with a fractional distillation column. On the right, you can see several chemical processors.

Identify the property of the components of crude oil that allow for its separation by fractional distillation

Separation of crude oil is possible by fractional distillation because it is a mixture of compounds with different boiling points.

Identify the products of crude oil refinery and describe their uses

The different products of crude oil refinery and their uses are:

Refinery Gas – Fuel and as starting material in the manufacture of plastics and petrol additives

Gasoline (Naphtha, Petrol) – Motor fuel, naphtha for manufacture of petrochemicals, solvents

Kerosene – Aviation fuel, starting material for catalytic cracking process to produce other organic compounds

Diesel – Diesel fuel, heating fuel oil, fuel for industrial boilers, starting material for catalytic cracking process to produce other organic compounds

Lubricating oils – Lubricating oil, starting material for catalytic cracking process to produce other organic compounds

Paraffin waxes – Candles, wax paper

Bitumen – Roofing tar, road bitumen (asphalt)

Identify any wastes that arise from the refinery of crude oil and discuss any issues (environmental, health issues) that are associated with these wastes

The refining process releases various chemicals into the atmosphere. This leads to an odour in the surrounding vicinity of the refinery, which means that refineries are situated far from urban areas. Also associated with refineries are wastewater issues, and noise health effects.

Crude oil contains sulphur. During the refinery process this sulphur is released from the crude oil. This waste may be recovered but may also leak out into the atmosphere. Hydrocarbon vapours may be produced in the refinery process. To prevent it from polluting the atmosphere, refineries use floating roofs or a recovery system. Hydrogen sulphide is a toxic gas that is created from hydrotreating (a process using sodium hydroxide (caustic soda) to remove contaminants). This is converted to sulphur, which is non-toxic and useful.

Contamination due to leakage of oil or other chemicals may occur. This can have a major impact on soil. Oils can cause water pollution if leaks are undetected.

Part 2: Although most elements are found in combinations on Earth, some elements are found un-combined

2.1: explain the relationship between the reactivity of an element and the likelihood of its existing as an un-combined element

Some elements are more reactive than others. This is due to how elements want to lose or gain electrons to create a full shell. The less electrons the element needs to gain or lose to achieve noble gas configuration, the more reactive it is. The more reactive an element is, the more likely it will exist combined with other elements as a compound. The converse is also true: Elements found in their pure form are less reactive. This is because reactive elements will combine (react) together or with other reactive elements in nature easily. So elements that are very reactive will be unlikely to find as un-combined elements, and elements that are more stable will be likely to find as un-combined elements.

2.2: classify elements as metals, non-metals and semi-metals according to their physical properties

Property   Metals   Non-metals   Semi-metals   Physical state at room temperature (20°C)  

Solid except mercury  Mostly gas, some solid except bromine (liquid) 

Solid 

Electrical Conductivity   Good  Very poor  Poor Thermal Conductivity   Good  Very poor  Poor Melting Point   Usually high  Usually low  High Boiling Point   Usually high  Usually low  Usually high Lustre   Lustrous  Dull  Variable Malleable   Usually   Brittle (No)  Variable Ductile   Usually   Brittle (No)  Variable Examples   Aluminium, lithium  Chlorine, carbon  Silicon, arsenic Uses   Jewellery, building

materials, batteries, utensils 

Noble gases - neon lights Chlorine - water treatment 

Silicon - Computing Chips

2.3: account for the uses of metals and non-metals in terms of their physical properties

Metals – Wires because of ductility, sheets because of malleability, and structural components because of strength. Copper wires – ductility, electrical conductivity. Iron structural components – malleability, strength.

Non-metals – Noble gases used in ‘neon’ lights because of its stability, chlorine is used in water treatment because of its reactivity.

2.a: plan and perform an investigation to examine some physical properties, including malleability, hardness and electrical conductivity, and some uses of a range of common elements to present information about the classification of elements as metals, non-metals or semi-metals

Aim: To examine several physical properties of metals, non-metals or semi-metals

Method:

1. To test malleability, try to bend the sample. 2. To test for lustre, lightly sand the sample. Then determine if the sample is shiny.

3. To test for hardness, use an iron nail to try to scratch the surface of the sample. If it does, the sample is softer than iron, and if it doesn't scratch, the sample is harder than iron.

4. To test for electrical conductivity, create an electrical circuit. The place the sample into the circuit. If the light turns on, the element is a conductor. If it doesn't, the element is an insulator.

2.b: analyse information from secondary sources to distinguish the physical properties of metals and non-metals

2.c: process information from secondary sources and use a Periodic Table to present information about the classification of elements as:- metals, non-metals and semi-metals- solids, liquids and gases at 25 degrees C and normal atmosphere pressure

Part 3: Elements in Earth materials are present mostly as compounds because of interactions at the atomic level

3.1: identify that matter is made of particles that are continuously moving and interacting

All matter is made of particles that are continuously moving and interacting – even in solids the particles vibrate in place.

3.2: describe qualitatively the energy levels of electrons in atoms

Electrons are arranged in energy shells around the nucleus. The energy levels (shells) of the electrons increase in energy the further they are from the nucleus. Each energy level can only accommodate a set maximum amount of electrons. Each shell must be filled before electrons can be placed on the next energy level.

Shell Number Max Number of electrons1 22 83 84 18

3.3: describe atoms in terms of mass number and atomic number

The atomic number of an atom is:

- Number of protons in an atom- Is different for every type- Defines what the atom is

The mass number of an atom is:

- Sum of protons + neutrons

Therefore the number of neutrons can be determined by [Mass Number – Atomic Number].

3.4: describe the formation of ions in terms of atoms gaining or losing electrons

An ion is a charged particle. All atoms seek to have a complete valence shell to become unreactive. A cation (metals + H) is an atom that loses electrons and are positively charged. An anion (non-metals except H) is an atom that gains electrons and are negatively charged.

3.5: apply the Periodic Table to predict the ions formed by atoms of metals and non-metals

Group I 1+Group II 2+Group III 3+Group IV 4+ or 4-Group V 3-Group VI 2-Group VII 1-Group VIII 0

3.6: apply Lewis electron dot structures to:- the formation of ions- the electron sharing in some simple molecules

3.7: describe the formation of ionic compounds in terms of the attraction of ions of opposite charge

The electrostatic attraction between a cation and an anion where electrons are transferred from the cation to the anion.

3.8: describe molecules as particles which can move independently of each other

Molecules can move independently of each other. Always covalently bonded.

3.9: distinguish between molecules contain one atom (the noble gases) and molecules with more than one atom

Molecule:

- Atoms- 1 atom (noble gases)- 2 or more atoms (element e.g. O2), (compound e.g. CO2)

3.10: describe the formation of covalent molecules in terms of sharing of electrons

Covalent bonds are formed between non-metal elements (that need to gain electrons). In covalent bonds the atoms share the available electrons to ensure they have a full valence shell. The number of covalent bonds formed by an atom depends upon the number of electrons in the valence shell. Covalent bonding can exist between different types of atoms and atoms of the same element.

3.11: construct formulae for compounds formed from:- ions- atoms sharing electrons

Ions: CaO, AlCl3, Ag2O

Covalent: PCl3, SF4, N2O3

3.a: analyse information by constructing or using models showing the structure of metals, ionic compounds and covalent compounds

3.b: construct ionic equations showing metal and non-metal atoms forming ions

Cations (metals): K → K+ + e-

Mg → Mg2+ + 2e-

Al → Al3+ + 3e-

Anions (non-metals): Cl + e- → Cl-

S + 2e- → S2-

N + 3e- → N3-

Part 4: Energy is required to extract elements from their naturally occurring sources

4.1: identify the differences between physical and chemical change in terms of rearrangement of particles

Physical Changes Chemical Changes- Volume- Density- Change of state- Change in shape- Breaking of intermolecular bonds- Relatively small amounts of energy

- New substances- Not easy reversed- Breaking of intramolecular bonds- Relatively large amounts of energy

Examples of physical changes: Melting ice, bending substancesExamples of chemical changes: Decomposition, baking a cake, exposing photo film to light

4.2: summarise the difference between the boiling and electrolysis of water as an example of the difference between physical and chemical change

The boiling of water is a physical change and only intermolecular forces are broken. This only takes 44KJ per molecule. The electrolysis of water is a chemical change and covalent, intramolecular bonds are broken. This takes 286KJ per molecule. Because intramolecular

bonds are stronger than intermolecular bonds, more bond energy (energy required to break the bond) is required.

4.3: identify light, heat and electricity as the common forms of energy that may be released or absorbed during the decomposition or synthesis of substances and identify examples of these changes occurring in everyday life

Decomposition is the breaking down of a molecule into simpler substances and/ or constituent elements. Synthesis is when a compound is made from other compounds or elements. Everyday examples include:

- Heat: Baking a cake (2NaHCO3 (s) Na2CO2 (s) + CO2 (g) + H2O (g))- Light: Developing film on photos (AgBr (s) Ag (s) + Br (s))- Electrical: Extraction of metals

4.4: explain that the amount of energy needed to separate atoms in a compound is an indication of the strength of the attraction, or the bond, between them

The amount of energy needed to separate the atoms in a compound is proportionate to the strength of the bond between atoms in that compound. For example, ionic bonds have a higher amount of bond energy than covalent because they are stronger than covalent bonds.

4.a: plan and safely perform a first-hand investigation to show the decomposition of a carbonate by heat, using appropriate tests to identify carbon dioxide and the oxide as the products of the reaction

4.b: gather information using first-hand or secondary sources to:- observe the effect of light on silver salts and identify an application of the use of this reaction- observe the electrolysis of water, analyse the information provided as evidence that water is a compound an identify an application of the use of this reaction

Decomposition: 2H2O (l) 2H2 (s) + O2 (g)

Synthesis: 2H2 (g) + O2 (g) 2H2O (l)

The above picture shows the application of the electrolysis of water: to power a car (hydrocar)

4.c: analyse and present information to model the boiling of water and the electrolysis of water tracing the movements of and changes in arrangements of molecules

Part 5: The properties of elements and compounds are determined by their bonding and structure

5.1: identify differences between physical and chemical properties of elements, compounds and mixtures

Physical properties are those related to changes of state and physical changes, this includes hardness, conductivity, lustre, melting point.

Chemical properties are those related to chemical changes, this includes solubility, reactivity.

The physical and chemical properties of elements, compounds and mixtures would differ as they all consist of different structures, such as bonding and valency.

5.2: describe the physical properties used to classify compounds as ionic or covalent molecular or covalent network

Bonding  Melting and Boiling Points 

Electrical Conductivity 

Soluble in Water 

'Hammer' Test (illustrates bonding) 

Hardness and Malleability

Metallic  High  Good  No  Flattens  Hard, Malleable

Ionic  High  Only in molten states 

Yes  Forms powder 

Hard, Brittle

Covalent Molecular 

Low  Poor  No  Forms powder 

Soft, Brittle

Covalent Network 

Very High  Poor  No  Shatters Very Hard, Brittle

5.3: distinguish between metallic, ionic and covalent bonds

Ionic: Strong bonds. The electrostatic attraction between a cation and anion, resulting in a transfer of electrons from the cation to the anion.

Covalent: Bonds are not as strong as ionic bonds. Electrons are shared between two anions.

Metallic: The type of chemical bond between atoms in a metallic element, formed by the valence electrons moving freely through the metal lattice.

5.4: describe metals as three-dimensional lattices of ions in a sea of electrons

Metallic bonding involved metallic cations in a three-dimensional lattice structure, held together by a sea of delocalised electrons. The delocalised electrons hold the structure together when distorted, making the metals ductile and malleable. The electrons being delocalised makes it able to conduct electricity efficiently. The lattice structure makes it hard.

5.5: describe ionic compounds in terms of repeating three-dimensional lattices of ions

The ions in ionic compounds are arranged in repeating three dimensional lattices. The electrostatic force between the ions makes ionic compounds strong, but when the lattice is distorted, the opposite charges line up and repel, thus ionic compounds are brittle. This also means that when ionic compounds are in the solid form, they do not conduct electricity as the lattice prevents any mobile charged species. However, when molten, the lattice is broken up, allowing ions to move, and the compound can conduct electricity as it now contains mobile charged species.

5.6: explain why the formula for an ionic compound is an empirical formula

An empirical formula is a formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms. The formula for an ionic compound is an empirical formula because ionic compounds are repeating units; there are no discrete molecules. Thus the simplest repeating unit is used for the formula for an ionic compound.

5.7: identify common elements that exist as molecules or as covalent lattices

Ionic: sodium chloride, silver fluoride, lithium nitrate, titanium oxideCovalent molecular: oxygen gas, hydrogen gasCovalent network: diamond (carbon), silicon dioxide, silicon monocarbideMetallic: iron, magnesium, silver

5.8: explain the relationship between the properties of conductivity and hardness and the structure of ionic, covalent molecular and covalent network structures

Ionic: No mobile charged species in the lattice structure while it is solid – resulting in non-conductivity. When in a molten or aqueous state, ions are able to move through the melt, resulting in conductivity.

Covalent molecular: Non-conductors of electricity in both the solid and liquid states because of the lack of mobile charged species – no ions or delocalised electrons capable of conducting an electric current.

Covalent network: Non-conductors of electricity in both the solid and liquid states because of the lack of mobile charged species – no ions or delocalised electrons capable of conducting an electric current. This is a result of the strong intramolecular covalent bonds that hold the lattice together.

5.a: perform a first-hand investigation to compare the properties of some common elements in their elemental state with the properties of the compound(s) of these elements (eg magnesium and oxygen)

5.b: choose resources and process information from secondary sources to construct and discuss the limitations of models of ionic lattices, covalent molecules and covalent and metallic lattices

A model is a physical device (animation or diagram) that depicts/predicts how an object/phenomenon functions. These ‘analogies’ help us to visualise and conceptualise abstract ideas, that may otherwise be difficult to understand. 

Benefits  Limitations 

Models can be used to represent complex phenomena 

Models help represent structures that are too small or too large to study 

Models help us visualise and conceptualise abstract ideas, which may otherwise be difficult to understand. E.g. globe of earth 

Most models cannot incorporate all the detail of a concept or phenomena 

Models are only accurate as the data used to construct it – if the data is no longer valid, the associated model becomes redundant 

E.g. a globe of the earth cannot sufficiently describe the depths of the earth 

5.c: perform an investigation to examine the physical properties of a range of common substances in order to classify them as metallic, ionic or covalent molecular or covalent network substances and relate their characteristics to their uses

8.3 Metals

Part 1: Metals have been extracted and used for many thousands of years

1.1: outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals or as alloys

Historical uses: Metals such as copper, gold and iron were used for weapons, ornaments and tools due to their malleability. Bronze is a significant early alloy as it was harder than copper and was used to create better tools and armour.

Contemporary uses: Copper, gold and silver were all original ‘coinage’ metals, being used as currency throughout the world. Copper is also used for wiring. An example of a contemporary metal is aluminium. This is used extensively in the modern day in the construction of buildings, domestic utensils (saucepans, cooking foil, drink cans), electrical transmission lines, telescope reflectors, and airplane casing. This is due to resistance to corrosion, low density (lightweight), malleability, and thermal and electrical conductivity. Titanium is another example of a metal used in alloys due to its high melting point, strength, low density and resistance to corrosion. It is used in aircraft engines, missiles and spacecraft.

1.2: describe the use of common alloys including steel, brass and solder and explain how these relate to their properties

Brass is hard and resistant to corrosion and is used for door knobs and screws due to their durability and resistance to weathering.

Steel is hard and strong, and is used in construction and for cutlery.

Solder is soft and has a low melting point, making it easier to use in conjunction with other metals to seal other metals together.

1.3: explain why energy input is necessary to extract a metal from its ore

Ores are metals bonded with other minerals or elements. Energy input is required to break these intermolecular bonds in order to extract the metal. Energy is also needed to mine the ores from the Earth. Chemical reactions are used for extraction, and every chemical reaction involves either the release or absorption of energy.

1.4: identify why there are more metals available for people to use now than there were 200 years ago

Technological advancements have made metals more readily available and easier to extract from ores. New alloys have been introduced as a result of continuous testing. Metals used to be very expensive to extract, but in the 20th century, the price of electricity decreased (electricity is used for the electrolysis and for keeping the electrolytes molten for aluminium). Thus the reducing cost of electricity and the availability of electricity has enable people to extract metals at a cheaper price, and more easily.

1.a: gather, process, analyse and present information from secondary sources on the range of alloys produced and the reasons for the production and use of these alloys

Alloy UsesBronze Church bells, statues, bearingsBrass Door knobs, screwsCupronickel Sinks, cutleryStainless Steel Sinks, cutleryMild Steel Nails, cables and chainsSolder Joining pipes wires

1.b: analyse information to relate the chronology of the Bronze Age, the Iron age and the modern era and possible future developments

The Bronze Age was from 3000 BC to 1000 BC. This was when bronze, an alloy of copper, was discovered. This was important during this time as bronze is harder than copper, yet malleable and ductile, allowing humans to create better tools and armour. The Iron Age is from 1000 BC onwards. This was when humans were able to extract iron from its ore. As iron is strong, and hard, this allowed humans to construct better buildings, machinery, tools.

Part 2: Metals differ in their reactivity with other chemicals and this influences their uses

2.1: describe observable changes when metals react with dilute acid, water and oxygen

Observable changes when metals react with water

K, Na, Ca  Reacts with cold water to form hydroxide ions and release hydrogen gas 

Mg  Reacts with hot water to form hydroxide ions and release hydrogen gas 

Al, Zn, Fe  React with steam at red heat to form oxide ions and release hydrogen gas 

Sn, Pb Cu, Hg, Ag, Au 

No reaction  

Observable changes when metals react with oxygen 

K, Na, Ca  Burn rapidly to form oxides or peroxides Mg, Al, Zn, Fe Burn readily if powdered or as fine fibres to form oxides Sn, Pb, Cu, Hg Become coated wisth oxide layers during heating Ag, Au  No reaction  

Observable changes when metals react with dilute acids 

K, Na  Foam very rapidly producing hydrogen gas, which may ignite Ca, Mg  Bubble rapidly releasing hydrogen Al, Zn, Fe, Sn, Pb 

Bubble moderately to very slowly as hydrogen is released; reaction is fast in warm acid; lead stops reacting when coated with insoluble PbCl2 or PbSO4 

Cu, Hg, Ag, Au 

No reaction

2.2: describe and justify the criteria used to place metals into an order of activity based on their ease of reaction with oxygen, water and dilute acids

Metals vary in reactivity. This is why they are tested with three different types of substances. Reactive metals will react with oxygen, and will vigorously react with water and dilute oxygen. Less reactive metals may react with oxygen, but may not react with water and dilute oxygen vigorously, placing them lower in the series. The least reactive metals will not react with anything. Thus by determining where each metal will react, we can make up an activity series which is a list of metals based on their order of reactivity.

2.3: identify the reaction of metals with acids as requiring the transfer of electrons

Oxidation/ reduction reactions involve the transfer of electrons. These reactions are referred to as redox reactions. Oxidation and reduction reactions must occur simultaneously as the substance being oxidised must donate electrons to another substance that is being reduced (and will accept the electrons). Oxidation is loss (electron donor), reduction is gain (electron acceptor). A substance that is reduced is also called an oxidising agent or oxidant as it causes another substance to be oxidised (lose electrons). A substance that is oxidised is also called a reducing agent or reductant as it causes another substance to be reduced (gain electrons).

Also refer to redox reactions sheet (it’s confusing).

2.4: outline examples of the selection of metals for different purposes based on their reactivity, with a particular emphasis on current development in the use of metals

2.5: outline the relationship between the relative activities of metals and their positions on the Periodic Table

The general reactivity of metals decreases across a period, and the reactivity of metals increase down a group.

2.6: identify the importance of first ionisation energy in determining the relative reactivity of metals

Ionisation energy is the energy required to remove an electron from an element.

The reactivity of metals increases as their ionisation energy decreases (the easier it is to remove an electron from a metal, the more reactive it is).

2.a: perform a first-hand investigation incorporating information from secondary sources to determine the metal activity series

Refer to prac notes.

2.b: construct word and balanced formulae equations for the reaction of metals with water, oxygen, dilute acid

2.c: construct half-equations to represent the electron transfer reactions occurring when metals react with dilute hydrochloric and dilute sulphuric acids

Part 3: As metals and other elements were discovered, scientists recognised that patterns in their physical and chemical properties could be used to organise the elements into a Periodic Table

3.1: identify an appropriate model that has been developed to describe atomic structure

3.2: outline the history of the Periodic Table including its origins, the original data used to construct it and the predictions made after its constructions

In 1829, Johann Dobereiner recognised that some elements could be grouped into threes, or triads, as they had similar properties. The four triads he formed were: chlorine, bromine and iodine; calcium, strontium and barium; sulfur, selenium and tellurium; lithium, sodium and potassium. In all the triads, the atomic weight of the middle element was almost the average of the atomic weights of the other two elements.

In 1864, English chemist John Newlands classified 64 of the known elements into eight groups, each group sharing similar physical properties. He referred to pattern of elements as the 'law of octaves', likening them to a musical scale. He also gave each element an atomic number based on their atomic weight.

Russian chemist Dimitri Mendeleev created the first periodic table that resembled the modern day table. He first sorted them by atomic weight, then into groups based on valencies. In 1871, he noted that there was a periodic relationship in the properties of the elements; similar properties were repeated every 8th element. From his table, Mendeleev asserted that some of the known atomic weights were wrong. He also left gaps for elements not yet discovered, and even predicted the physical properties of a few of the unknown elements, such as germanium, which he called eka-silicon.

3.3: explain the relationship between the position of elements in the Periodic Table, and:- electrical conductivity- ionisation energy- atomic radius- melting point

- boiling point- combining power (valency)- electronegativity- reactivity

Electrical Conductivity

Trend across a period:

- Decrease in electrical conductivity- Related to change from metals through semi-metals to non-metals across a period.

Metals can conduct electricity (delocalised electrons), but non-metals cannot.

Ionisation Energy – the amount of energy needed to remove an electron from the valence shell

Across a period:

- Ionisation energy increases- The increase in ionisation energy across a period is due to each successive element

having one more proton in its nucleus. The extra electron for successive elements in a period occurs in the same energy levels as other valence electrons. Therefore a gradual increase in attractive forces between valence electrons and nucleus.

Down a group:

- Ionisation energy decreases as the valence electrons are further from the nucleus in each successive period, therefore the attractive forces lessen.

Atomic Radius – distance from the nucleus to the valence shell

Across a period:

- Atomic radius decreases- The radius decreases because the increasing positive charge of the nucleus pulls the

outermost electrons, which are in the same energy level, closer to the nucleus.

Down a group:

- Atomic radius increases as each new period adds another electron energy shell which is more distant from the nucleus than the previous electron level.

Melting and Boiling Points

Trend across a period:

- Generally rise to the elements in group IV and then decrease- Related to the bonding type of the elements which change from metallic to covalent

network to covalent molecular across a period- E.g. melting points of elements in Period 2 (degrees C): Li = 180, Be = 1278, B =

2300, C = 3727, N = -210, O = -219, F = -220.

Combining Power (Valency)

Trend across a period:

- Valency increases to group IV and then decreases due to the number of electrons in the valence shell

Reactivity

Trend across a period:

- Decreases from group I to group IV- Increase from group IV to group VII- Group VIII elements unreactive (inert)

Trend down a metallic group:

- Reactivity increases, as valence electrons are further from the positive nucleus in each successive period (therefore valence electrons are more easily lost). Therefore, a reactive metal will have a low ionisation energy and low electronegativity.

Trend down a non-metallic group:

- Reactivity decreases, as valence electrons are further from the positive nucleus in each successive period (therefore valence electrons are less easily gained/ attracted). Therefore, a reactive non-metal will have a high ionisation energy and high electronegativity.

3.a: process information from secondary sources to develop a Periodic Table by recognising patterns and trends in the properties of elements and use available evidence to predict that characteristics of unknown elements both in groups and across periods

Refer to the large labelled periodic table in notes.

3.b: use computer-based technologies to produce a table and a graph of changes in one physical property across a period and down a group

Refer to “Ionisation Energy” booklet in notes.

Part 4: For efficient resource use, industrial chemical reactions must use measured amounts of each reactant

4.1: define the mole as the number of atoms in exactly 12g of carbon-12 (Avogrado’s number)

Avogrado’s number is 6.022 x 1023. One mole of a substance always contains the same number of particles no matter what the substance is.

Number of moles = number of particles/ Avogrado’s number

The relative molecular mass (or molecular weight) of a compounds is the mass of a molecule of the compound relative to the mass of an atom of the carbon-12 isotope which is taken as exactly 12.

The molecular weight of a compound is the sum of the atomic weights of the atoms as given in the molecular formula. The relative formula mass (or formula weight) of a compounds is the sum of the atomic weights of the atomic species given in the stated formula of that compound. If for any element we take the mass which in grams is numerically equal to the

atomic weight, then it contains 6.02 x 10^23 atoms. The molar mass is the mass of a mole of the substance. It can used for both elements and compounds. It is measured in gmol-1.

4.2: compare mass changes in samples of metals when they combine with oxygen

Percentage composition of a chemical compound specifies the percentage by mass of each of the different elements present in the compounds.

4.3: describe the contribution of Gay-Lussac to the understanding of gaseous reactions and apply this to an understanding of the mole concept

Gay-Lussac found that 2 volumes of Hydrogen and 1 volume of Oxygen would react to form 2 volumes of gaseous water. Based on Gay-Lussac's results, Amedeo Avogadro theorized that, at the same temperature and pressure, equal volumes of gas contain equal numbers of molecules (Avogadro's law).

4.4: recount Avogrado’s law and describe its importance in developing the mole concept

Avogrado’s law is “When measured at the same temperature and pressure, equal volumes of gases will contain the same number of molecules”. This law was significant in developing the mole concept as equal quantities of molecules is the basis for the mole concept.

4.5: distinguish between empirical formulae and molecular formulae

4.a: process information from secondary sources to interpret balanced chemical equations in terms of mole ratios

A chemical equation shows the relationship between the numbers of moles of reactants in a chemical reaction.

e.g. N2 (g) + 3H2 (g) 2NH3 (g)

mol: 1 : 3 2

4.b: perform a first-hand investigation to measure and identify the mass ratios of metal to non-metal(s) in a common compound and calculate its empirical fomula

4.c: solve problems and analyse information from secondary sources to perform calculations involving Avogrado’s number and the equation for calculating the number of moles of a substance:

n = m/ MM

4.d: process information from secondary sources to investigate the relationship between the volumes of gases involved in reactions involving a metal and relate this to an understanding of the mole