CHEMICAL EARTHElectrolysis: the decomposition of a chemical substance (in solution or the molten state) by the application of electrical energy

Identify the difference between elements, compounds and mixtures in terms of particle theory

- Element: made up of identical atoms- Compound: a pure substance composed of simpler substances with 2 or more elements

chemically bonded - Molecule: the smallest unit of a substance containing 1 or more elements (can be 1 atom)

Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds

Atmosphere - Mixture of gases(mostly elements)- Nitrogen, oxygen, argon- Water, carbon dioxide, nitrogen dioxide…

Hydrosphere - Water, carbon dioxide, sodium/calcium/magnesium chlorids/sulfates- Oxygen, nitrogen

Lithosphere - Rocks: silicon, oxygen, various metals- Sand: silicon dioxide, ground-up shells, dirt- Mineral ores- Coal, oil, natural gas

Biosphere - Carbon-containing compounds: proteins, fats, vitamins

Identify and describe procedures that can be used to separate naturally occurring mixtures of:

- Solids of different sizeso Sieving – separate small particles from large ones (eg. at quarries fine sand

separated from coarser material)- Solids and liquids

o Filtration – liquid/solution passes through paper, suspended solid stays on topo Sedimentation + decantation – solid settles to bottom and liquid carefully poured

off - Dissolved solids in liquids

o Evaporation – liquid heated to temp below BP so particles vaporise o Boiling – liquid heated to BP so liquid vaporises and solid remains

- Liquidso Distillation (if BP sufficiently different) – substance heated to boiling liquid with

lower BP vaporises first vapour rises and diffuses down side arm into water-cooled condenser condenses and collected as liquid

o Fractional distillation (similar BP) – fractionating column allows repeated condensation/vaporisation eventually pure sample of more volatile emerges

o Separating funnel (immiscible liquids) – put in separating funnel run off bottom liquid

- Gases o Distillation/fractional distillation – gases liquefied fractionally distilledo Solubility – pass mixture though bubbler + U-tubes dissolves some gases,

condenses some Eg. natural gas (containing CO2, hydrogen sulfide, water

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

- Natural gas (above) – uses different solubilities, boiling points- Saltwater – evaporation uses boiling points- Crude oil – fractional distillation uses diff. but similar BPs- Argon from air – fractional distillation separates nitrogen, then argon, then oxygen (diff. but

similar BPs)

Describe situations in which gravimetric analysis supplies useful data for chemists and other scientists

- The process of separating components of an original mixture to find the composition of a mixture in terms of grams and percentage mass that involves weighing

- A mining company wants to know composition of particular ore sample to see if it’s economic to mine the ore

Apply systematic naming of inorganic compounds as they are introduced in the laboratory

Identify IUPAC names for carbon compounds as they are encountered

Explain the relationship between the reactivity of an element and the likelihood of its existing as an uncombined element

- The more reactive less chance of finding it in earth as an uncombined element- Because if more reactive then when contact with other elements it may react to form

compounds

Classify elements as metals, non-metals and semi-metals according to their physical properties

Metals Non-metals Semi-metalsUsually solid at room temp (high BP)

Usually gas/liquid (low BP) Properties of both classes

Shiny/lustrous appearance DullConduct heat/electricity Don’t conduct electricity/little

heat conductivityMalleable and ductile Brittle High strength Low strength

Account for the uses of metals and non-metals in terms of their physical properties

METALS Use – Properties NON-METALS Properties

Aluminium Aircraft – low density Carbon graphite Electrodes – electrical conductivityLubricant – slippery/soft

Iron Motor cars/trains – high tensile strength

Carbon diamond Jewellery – very hard, scatters light (high refractive index)

Copper Electrical wiring – high electrical conductivity

Liquid nitrogen Cooling agent – suitability of MP/BP

Tungsten Filaments in light bulbs – high MP

Identify that matter is made of particles that are continuously moving and interacting

Describe qualitatively the energy levels of electrons in atoms

- Electrons surround nucleus by orbiting in discrete energy levels- Each energy level accommodates certain number of electrons and has certain amount of

energy- Number of electrons: 2n2

- Electron configuration: arrangement of electrons in energy levels

Describe atoms in terms of mass number and atomic number

- Atom consists of nucleus with proton/neutron and electron cloud - Atomic number: number of protons in nucleus- Mass number: protons + neutrons

Describe the formation of ions in terms of atoms gaining or losing electrons

- Atoms can transfer electrons to obtain noble gas configurations - When an atom gains or loses an electron to obtain ^ it becomes an ion- Because not equal number of protons/electrons – atom is positively/negatively charged

Apply the periodic table to predict the ions formed by atoms of metals and non-metals

Apply lewis electron dot structures to:

- The formation of ions

- The electron sharing in some simple molecules

Describe the formation of ionic compounds in terms of the attraction of ions of opposite charge

- Ions are positively/negatively charged - When an atom transfers electrons, forming ions – there is strong electrostatic attraction

between the ions of opposite charge – holds them together in ionic compound/bonding

Describe molecules as particles which can move independently of each other

Distinguish between molecules containing one atom (noble gases) and molecules with more than one atom

Describe the formation of covalent molecules in terms of sharing of electrons

- Covalent bonds formed between pairs of atoms by atoms sharing electrons – shared pair of electrons orbits nuclei of both atoms – holding atoms together in covalent molecule

- Covalent molecule made up of atoms covalently bonded by sharing electrons- Covalent molecular substance: made up of covalent molecules

Construct formulae for compounds formed from:

- Ions- Atoms sharing electrons

Identify the differences between physical and chemical change in terms of rearrangement of particles

- Chemical: breaks up particles and rearranges the atoms - Physical: rearrange particles without changing their nature

Summarise the differences between the boiling and electrolysis of water as an example of the difference between physical and chemical change

Boiling ElectrolysisNo new substance – converts liquid water to gaseous

Produces 2 new substances

Easily reversed – cool the vapour to liquid Hard to reverseLess energy required Much more energy required

- Boiling doesn’t alter particles (molecule) only separates them from each other – water vapour contains same water molecules as liquid water

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: o Calcium carbonate (limestone) decomposed to make lime, cement, glasso Aluminium extracted by electrolysing molten aluminium oxide

- Direct combination:o Rusting of iron to form iron(III) oxide o Lightning creates such high temp that N2 and O2 gases form nitric oxide

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

- Stronger the bonds/strength of attraction – more energy needed to separate the atoms - Stronger the chemical bonding – the more energy released when the compound is formed

Identify differences between physical and chemical properties of elements, compounds and mixtures

Physical ChemicalElements - Metals

- Non-metals- Semi-metals

- Metals: form cations/basic oxides/ionic chlorides

- Non-metals: form anions/acidic oxides/covalent chlorides

Compounds

- Ionico Solido Solubleo Conduct electricity when

dissolved in solution (not solid)- Covalent molecule

o Don’t conduct electricityo Low MPo Soft, brittle

- Different chemical properties to constituent elements

- Can be decomposed to component elements/simpler compounds

- Covalent networko Non-conductorso Insolubleo Very high MPo Very hard/brittle

Mixtures - Heterogenouso Demonstrate physical properties

of constituent substanceso Don’t look same throughout

mixture- Homogenous

o Physical properties of constituent substances

o Looks same throughout

- Demonstrate chemical properties of constituent pure substances

Describe the physical properties used to classify compounds as ionic, or covalent molecular or covalent network

- Ionico Solid at room tempo Hard/brittleo Conduct electricity as liquid/dissolved

- Covalent molecularo Gases/liquidso Don’t conduct electricity

- Covalent networko Solid – very high MPo Hard o Don’t conduct electricity except graphite

Distinguish between metallic, ionic and covalent bonds

Metallic Ionic Covalent Lattice of positive metal ions in ‘sea’ of delocalised electrons

Electrostatic attraction between positive cation and negative anion caused by transfer of electrons

Sharing of electrons between atoms – shared pair of electrons orbits nuclei of both atoms, holding them together

Describe metals as three-dimensional lattices of ions in a sea of electrons

- Delocalised electrons lost from valence shell of metal atom – positive ions- Attraction between positive metal ions/delocalised electrons is metallic bonding

Describe ionic compounds in terms of repeating three-dimensional lattices of ions

- Ionic compounds: infinite 3D array of cations and anions bonded by electrostatic attraction

Explain why the formula for an ionic compound is an empirical formula

- No discrete molecules, just infinite array of cations/anions- Simplest ratio of ions present in the crystal determines empirical formula of ionic

compound

Identify common elements that exist as molecules or as covalent lattices

Molecules: oxygen gas, carbon dioxide, water

Covalent lattice: diamond, sand (silicon dioxide)

Explain the relationship between the properties of conductivity and hardness and the structure of ionic, covalent molecular and covalent network structures

IONIC

Hard and brittle - Ions tightly bound by electrostatic forces- Breaking lattice forces like charged ions together, when forced

together they repel – accounts for hardness/brittlenessNon-conductor as solid - Ions in fixed positions

- Electrons strongly held by nuclei of ions – no free electronsConductor as liquid/dissolved

- Mobile ions can transfer electric charge

COVALENT MOLECULAR

Soft - Intermolecular forces are weakNon-conductor of electricity

- Molecules are uncharged- Electrons are localised in covalent bonds/with atoms

COVALENT NETWORK

Hard and brittle - Atoms strongly bound in covalent bonds- Strong covalent bonds – very hard

Non-conductor of electricity

- Electrons are localised in covalent bonds or with atoms

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

Metal Use Copper - Over 8000yrs

- Electrical wiring- Pipes and plumbing fittings- Electroplating, jewellery, household decorations

Iron and steel (alloy of iron)

- History: tools/weapons- Railways, bridges, buildings- Motor car bodies, ships, trains, heavy machinery in industry- Pipes, nails, nuts, bolts- Fridge, washing machine, domestic appliances

Lead - Car batteries- Plumbing and in solder

Aluminium - Buildings (window/door frames, panelling)- Aeroplanes, motor car parts- Domestic pots/pans, wrapping foil, drink containers- High voltage transmission lines

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

Metal Use How the use is related to propertiesBrass (50-60% copper with zinc)

- Plumbing fittings- Musical

instruments, decorations

- Lustrous gold appearance decorations/musical instruments

- Hard but easily machined plumbing fittings

Bronze (80-90% copper with tin)

- Ships’ propellers- Casting statues

- Hard, resists corrosion, easily cast

Solder (30-60% tin with lead)

- Joining metals together in plumbing/electronics

- Low melting point and adheres firmly to other metals when molten joining metals

Mild Steel (<0.2% carbon)

- Car bodies, pipes, nuts and bolts, roofing

- Soft, malleable roofing

Chrome steel (2-4% chromium)

- Safes, files, ball bearings

- Hard, shock resistant structural purposes

Stainless steels (10-20% chromium, 5-20% nickel)

- Food processing machinery, kitchen sinks and appliances, cutlery, surgical and dental instruments, razor blades

- Hard, resist corrosion knives/hammers

Explain why energy input is necessary to extract a metal from its ore

- Most metals found in minerals and energy necessary to extract metal from compound/mixture

- Energy required to break metal ion-oxide bonds in the ore to separate pure metal from other substances

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

- Technology/science developed (eg. electricity, nuclear reactors) better metal extraction techniques to extract more reactive metals (eg. aluminium) from compounds in nature

- Development of metallurgical skills for making new alloys

Describe observable changes when metals react with dilute acid, water and oxygen

- Metal + oxygen metal oxideo Those that burn (eg. Mg) will form crystalline white solids with no physical

properties of original (lustre, strength, malleability, conductivity)o Those that react slowly in room temp. (eg. Al, Zn) lose shiny lustre and some (Al,

Zn) are coated in dull layer of oxide preventing further reaction - Metal + water metal hydroxide + hydrogen

o Bubbles of H2

o Na and K often produce flame as H2 ignites o Some produce precipitate (calcium hydroxide)

- Metal + dilute acid salt + hydrogeno Bubbles of H2

o If salt insoluble then precipitate formed

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

Sodium Magnesium Iron CopperOxygen Yes Yes No NoWater Yes Yes No NoAcid Yes Yes Yes No

- From table Na and Mg least reactive – sodium more reactive because reactions more violent

- Iron more reactive than copper because reacted in acid - Using reactions with water, acid, oxygen effective in ranking activities based on whether or

not they react + violence of reaction

Identify the reaction of metals with acids as requiring the transfer of electrons

- Reactions of metals with acids transfers electrons from metal metal becomes positive ions

Outline examples of the selection of metals for different purposes based on their reactivity, with a particular emphasis on current developments in the use of metals

- Non-reactive aluminium/cheaper galvanised iron – roof guttering for houses- Non-reactive copper/cheaper corrodible iron – water pipes- Cheap copper (forms non-conducting oxide layer)/gold – electrical contacts for replaceable

circuit boards in comp/electronics- Extremely inert titanium alloys/long term corrosion-susceptible stainless steel – body

implants

Outline the relationship between the relative activities of metals and their positions on the Periodic Table

- Group 1 most reactive, reactivity decreases across period- Reactivity increases down a group

Identify the importance of first ionisation energy in determining the relative reactivity of metals

- Ionisation energy decrease = reactivity increase

Identify an appropriate model that has been developed to describe atomic structure

- Dalton’s atomic theory (1803 and 1808):o Matter composed of tiny invisible particles called atomso All atoms of one element identical but diff from atoms of other elementso Chemical reactions consist of combining, separating, rearranging atoms in simple

whole number ratios

Outline the history of the development of the Periodic Table including its origins, the original data used to construct it and the predictions made after its construction

- 1829 Dobereiner drew attention to groups of 3 elements (triads) with similar propertieso Lithium, sodium, potassiumo Calcium, strontium, bariumo Chlorine, bromine, iodine

- 1864 John Newlands proposed ‘law of octaves’ elements arranged in order of increasing atomic weight

o 8th element starting from given one is like the firsto Identified many similarities among elements but required similarities where there

were none works up to calcium - 1869 Dmitri Mendeleev and Lothar Meyer produced forerunner of modern periodic table

o Elements arranged in increasing atomic weight similar elements placed under one another

o Periodic law: properties of the elements vary periodically with atomic weighto Mendeleev left gaps because recognised probs undiscovered elements

Predicted the properties of 6 undiscovered elements elements later discovered with properties very similar to his predictions

- 1914 Henry Moseley determined atomic number of elements which he proposed was basic feature to determine properties (instead of atomic weight)

o Modified periodic law: properties of elements vary periodically with atomic number Once recognised properties dependent on atomic number tendencies

towards relating layout of table to electron configuration developed current table developed

Explain the relationship between the position of elements in the Periodic Table and:

- Electrical conductivityo Decreases across periods

- Ionisation energyo Increase across periods (gaining another proton, electrons in same shell stronger

attraction)o Decrease down group (gaining another shell – electrons further from nucleus)

- Atomic radiuso Decrease across period (stronger attraction between electrons and protons)o Increase down group (gaining another shell)

- Melting pointo Highest in middle of period (bonding and structure)o Decreases down group (more outer shells attraction of electrons to nucleus

weaker)- Boiling point

o Highest in middle of period (bonding and structure)o Decreases down group (more outer shells attraction of electrons to nucleus

weaker)- Combining power (valency)

o Increases across period to group 4 where it goes back down and increases againo Same down a group

- Electronegativity

o Increase across periods (stronger attraction because more positive nucleus and outer electrons added to same shell)

o Decrease down group (outer electrons further away as they’re added to new shell – big atoms with more shell)

- Reactivityo Decrease across periodo Increase down period

Define the mole as the number of atoms in exactly 12g of carbon-12 (avogadro’s number)

- A mole of substance contains as many elementary units as number of atoms in exactly 12g of Carbon-12

- This number is Avogadro’s number = 6.02 x 1023

Compare mass changes in samples of metals when they combine with oxygen

- OEI, burning Mg to MgO mass increase (all metals)

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

- Gay-Lussac’s law of combining volumes: o When measured at constant temp and pressure, volumes of gases in chemical

reaction show simple whole number ratios to one another Mole ratios can be considered as volume ratios Volume of gaseous product/reactant can be used to calculate amount of

another gaseous product/reactant Can use results from quantitative analyses of compounds/reactions to

determine formulae for compounds + relative atomic masses for elements existence of formulae/atomic weights + ability to write chemical

equations essential for talking about moles critically important

Recount Avogadro’s law and describe its importance in developing the mole concept

- At same temp and pressure, equal volumes of gases contain same number of molecules (vice versa)

- (same as above) determined formulae + atomic masses for elements existence of formulae/atomic weights + ability to write chemical equations essential for talking about moles critically important

Distinguish between empirical formulae and molecular formulae

- Empirical: ratio in which atoms are present in compound- Molecular: how many of each type of atom in a molecule of the compound

Define the terms mineral and ore with reference to economic and non-economic deposits of natural resources

- Ore: mineral of economic value, defined on economics only defined as ore if commercially viable

- Mineral: compound found in rocks

Describe the relationship between the commercial prices of common metals, their actual abundances and relative costs of production

- Prices affected by abundance, location, cost of extraction, cost of transportation, world-wide demand

- Less abundance ores generally higher royalties more expensive- Expensive to extract higher price

- If shipped from remote location higher price

Explain why ores are non-renewable resources

- They were formed when earth was formed and no way of forming more of them

Describe the separation processes, chemical reactions and energy considerations involved in the extraction of copper from one of its ores

1. Ore is mined then crushed2. Froth floatation to concentrate ores

a. air blown through tiny jets into detergent solutionb. froth formsc. particles wetted by solution sink to bottom, particles not wetted are drawn inside

the bubbles and float to surfaced. froth is skimmed off and is richer in non-wettable particles than the starting

minerale. by adding certain oils to finely crushed ore, sulfide particles can be made non-

wettable so can be separated out (most copper ores in aus are sulfides)3. Copper concentrate heated with sand produce 2 immiscible liquids: one mainly copper

sulfide, one with unwanted iron silicate (discarded)a. Remaining iron in second liquid removed by reheating with more sand and air

bubbled through it4. Copper sulfide liquid heated with air bubbled through it reduces sulfide to copper metal,

sulphur dioxide produceda. Some sulphur dioxide doesn’t leave until cooling copper almost solid blister

copper – 98% pure 5. Copper can be purified to 99.95% by electrolysis

Chemical reactions

- Copper sulfide with oxygen:o Cu2S (l) + O2 (g) 2Cu (l) + SO2 (g)

- Chalcopyrite, silica (sand) and oxygen copper sulfide, iron silicate, sulfur dioxideo 2CuFeS2 (s) + 2SiO2 (s) +4O2 (g) 2Cu2S (l) + 2FeSiO3 (l) + 3SO2 (g)

Energy considerations

- Large amount of energy needed to extract metal from ore- Energy needed to:

o Mine the oreo Purify/concentrate the oreo Maintain high temp to make extraction reactions goo Purify raw metal/form it into useful alloys

Energy required for production of 1kg of certain metals

Metal From natural ores (megajoules) From recycled material (megajoules)

Aluminium 200 7Copper 70 4Mild steel 40 8

Recount the steps taken to recycle aluminium

1. Collect used products from homes, shopping centres, factories etc2. Transport to central processing plant3. Separate aluminium from impurities (eg. labelling, food remnants, dirt)4. Re-smelt into ingots and transport to product manufacturers

WATERSolute: minor component of solution, dissolved in solvent

Solvent: major component of solution which dissolves solute

Solution: a homogenous mixture with a completely dissolved solute in solvent

Identify the importance of water as a solvent

Compare the state, percentage and distribution of water in the biosphere, lithosphere, hydrosphere and atmosphere

Outline the significance of the different states of water on Earth in terms of water as:

- A constituent of cells and its role as both a solvent and a raw material in metabolism

o Comprises approx. 70% of cells and keeps them turgido Solvent for life processes to occur (eg. metabolism)o Raw material in chemical reactions – essential for photosynthesiso Transports nutrients to cells and remove waste productso Thermal regulator by smoothing out sudden large temp changeo Metabolic water produced by respiration is important water source for living things

- A habitat in which temperature extremes are less than nearby terrestrial habitats

o Water bodies have less temp. fluctuation (high heat capacity) than land/airo Ice less dense than water float on surface of waterbody insulating layer allows

aquatic life to survive- An agent of weathering of rocks both as liquid and solid

o Ocean waves and rains wear surface rockso Glaciers wear away rocks and cause significant erosion as they move down valleys

from mountain top to oceano Freeze-thaw mechanism of water freezing cracking rocks

o Chemically weather rocks by reacting with minerals converting them to more easily eroded minerals

- A natural resource for humans and other organismso Drinking, food prep, washing, recreationo Irrigating crops and watering livestocko Fluid in electricity generating station and coolant in industrieso Hydro-electricity o Reactant, solvent, cleaning agent in industry and waste disposal, settling dusto Mode of transport

Construct Lewis electron dot structures of water, ammonia and hydrogen sulphide to identify the distribution of electrons

Compare the molecular structure of water, ammonia and hydrogen sulphide, the differences in their molecular shapes and in their melting and boiling points

Describe hydrogen bonding between molecules

- Intermolecular force involving H atom bonded to F,O,N in a molecule attracted to F,O,N bonded to H in another molecule

- F,O,N are 3 most electronegative and H is least electronegative significant negative dipole on F,O,N and significant positive dipole on H

- Stronger form of dipole-dipole force

Identify the water molecule as a polar molecule

Describe the attractive forces between polar molecules as dipole-dipole forces

- Polar molecules have a net dipole because electron pairs unevenly sharedo -> due to differences in electronegativityo Molecules line up so that positive end of one attracts negative end of anothero Electrostatic attraction acting between opp.-charged poles of the molecules

Explain the following properties of water in terms of its intermolecular forces:

- Surface tension: measure of resistance of a liquid to increasing its surface area - Viscosity: measure of resistance of a liquid to being poured or to flowing through a tube- Boiling and melting points: weaker forces = lower BP/MP (less energy needed to

overcome/break forces); stronger forces = higher BP/MP (more energy needed)

Explain changes, if any, to particles and account for those changes when the following types of chemicals interact with water:

- A soluble ionic compound (eg. NaCl)o Anions and cations in ionic compound break aparto Negative end of water surrounds the cationo Positive end of water surrounds anion

- A soluble molecular compound (eg. sucrose)o Break up into individual moleculeso Forms hydrogen bonds with water because contains many O – H groups

- A soluble or partially soluble molecular element or compound such as iodine, oxygen or hydrogen chloride

o Molecule has weak dispersion forces with water molecules o Because these forces are weak only slightly soluble

- A covalent network structure substance such as silicon dioxide o Insoluble no change because water can’t break the strong covalent bonds

between atoms

- A substance with large molecules, such as cellulose or polyethyleneo Insoluble no change because large molecule held together by hydrogen bonds in

orderly way that water can’t separate them from each other H-bonding with substance can occur but these aren’t sufficient because

substance so strongly H-bonded to itselfo Some large proteins are soluble because their complex structures don’t pack neatly

into crystals so water can separate molecules by H-bonding with it

Analyse the relationship between the solubility of substances in water and the polar nature of the water molecule

- Polar nature allows for H-bonding, dipole-dipole or dispersion interactions between water and substance

- Polar ends of water molecule surround the substance and break it apart by attracting oppositely charged particles OR

- Hydrogen bonding which occurs because of polar nature and breaks apart the substance

Identify some combinations of solutions which will produce precipitates, using solubility data

Describe a model that traces the movement of ions when solution and precipitation occur

- Saturated solution of lead nitrate add some lead nitrate crystals with radioactive lead- Half hour later amount of solid lead nitrate in solution is the same but some radioactivity

detected in solution – previously no radioactivity in solution concentration of lead ions in solution and mass of solid not changed

Identify the dynamic nature of ion movement in a saturated dissolution

- Ions moving from solid into solution at the same time as ions moving from solution back into solid

o Both occurring at equal rates so concentration of solution and mass of solid doesn’t change dynamic equilibrium

Describe the molarity of a solution as the number of moles of solute per litre of solution using c=n/v

- Molarity is number of moles of solute per litre of solution- Concentration of solute in terms of moles per litre (c=n/V)

Explain why different measurements of concentration are important

- Each method has advantage in particular situations- Commerce, industry, shopping – amount of solute present is main concern mass per unit

volume convenient easier to measure out volumes than mass- If solute liquid: volume per unit volume preferred because liquid measure in volumes

usually- Environmental context: concentrations quite low ppm give more manageable numbers- Quantities in chemical reactions: concentration in terms of moles convenient

Explain what is meant by the specific heat capacity of a substance

- Amount of heat required to raise temp of unit mass of substance by 1degree celcius (1 kelvin)

- Measured in joules per Kelvin per gram: J K-1 g-1

Compare the specific heat capacity of water with a range of other solvents

Explain and use the equation H = -mC T

- Change in heat = - mass x specific heat capacity x change in temp

Explain how water’s ability to absorb heat is used to measure energy changes in chemical reactions

- Because specific heart capacity of water known and if water mass known, temp change in water observed to work out heat change in water hence energy change in chemical reaction in/immersed in water

Describe dissolutions which release heat as exothermic and give examples

- Exothermic – dissolutions that release heat- Eg. dissolution of sodium hydroxide, sulfuric acid in water

Describe dissolutions which absorb heat as endothermic and give examples

- Endothermic – dissolutions that absorb heat- Eg. potassium nitrate in water, dissolution of ammonium chloride/silver nitrate

Explain why water’s ability to absorb heat is important to aquatic organisms and to life on earth generally

- High heat capacity stable temp allow aquatic organisms thrive- Water within cells provide necessary temp regulation all living organisms

survive/reproduce- Water in biosphere (oceans) moderates global temp more hospitable environment for all

life

Explain what is meant by thermal pollution and discuss the implications for life if a body of water is affected by thermal pollution

- Discharges into river/lake of quantities of hot water large enough to increase temp. of water body

- When river/lake water used for cooling in industry/electricity generation discharged back into river/lake but 10-15degrees hotter

- Oxygen less soluble in hotter water 5degree increase lowers O2 concentration but 10-15%

o Causes stress to organismso Increased metabolism rates increases demand for oxygen (but less oxygen)o Fish eggs don’t develop/hatch if temp too higho False temp. cues to aquatic life migration/spawning at wrong time of yearo Sudden temp. change kill fish eggso Lethal temp limits may be exceeded

ENERGYOutline the role of photosynthesis in transforming light energy to chemical energy and recall the raw materials for this process

- Photosynthesis is process plants transform light to chemical energy

Outline the role of the production of high energy carbohydrates from carbon dioxide as the important step in the stabilisation of the sun’s energy in a form that can be used by animals as well as plants

- Solar energy chemical energy – energy is stored in the glucose - Production of high energy carbohydrates (glucose) from CO2 stores sun’s energy in form

that can be used by animals and plants – carbs in plants are energy source for animals- Production of carbs by photosynthesis is main way solar energy collected for

plants/animals

Identify the photosynthetic origins of the chemical energy in coal, petroleum and natural gas

- Fossil fuels basically stored solar energy from photosynthesis

Identify the position of carbon in the periodic table and describe its electron configuration

- Electron configuration is 2, 4

Describe the structure of diamond and graphite allotropes and account for their physical properties in terms of bonding

Diamond GraphiteStructure - C atoms bonded to 4 other C atoms

- Tetrahedrally arranged - C atom bonded to 3 other C

atoms- Planar structure

Bonding - Covalent bonds/network - Covalent bonds/networkPhysical properties - Doesn’t conduct electricity

- Transparent and brilliant (orderly arrangement of atoms throughout)

- Conductor of electricity - Slipperiness/lubricating (weak

intermolecular forces between layers)

Identify that carbon can form single, double or triple covalent bonds with other carbon atoms

Explain the relationship between carbon’s combining power and ability to form a variety of bonds and the existence of a large number of carbon compounds

- Readily forms carbon-carbon bonds that can be single/double/triple- Readily forms cyclic compounds (rings) and straight and branched chain compounds

Describe the use of fractional distillation to separate the components of petroleum and identify the uses of each fraction obtained

Identify and use the IUPAC nomenclature for describing straight-chained alkanes and alkenes from C1 to C8

Meth, eth, prop, but

Compare and contrast the properties of alkanes and alkenes C1 to C8 and use the term ‘homologous series’ to describe a series with the same functional group

Homologous series: family of compounds represented by 1 general molecular formula

Alkanes Alkenes- MP/BP/dispersion forces increases with

molecular weight- Volatility decreases with increase

molecular weight- Insoluble (non-polar)- Don’t conduct electricity

- MP/BP/dispersion forces increase with molecular weight (but BP slightly lower than alkanes)

- Insoluble (non-polar)- Don’t conduct electricity

C1/C2 – C4

Gases Gases

C5 – C8 Colourless liquids Liquids

Explain the relationship between the melting point, boiling point and volatility of the above hydrocarbons, and their non-polar nature and intermolecular forces (dispersion forces)

- MP/BP increases as volatility decreases- Because they are non-polar – intermolecular forces are dispersion forces

Assess the safety issues associated with the storage of alkanes C1 to C8 in view of their weak intermolecular forces (dispersion forces)

- Extremely flammable and can be toxic- Weak intermolecular forces molecules held less strongly exist as gases/liquids so

harder to store- Also high volatility- Safety precautions

o Use well-maintained cylinders and fittings for gaseous hydrocarbonso Add odours for early detection of leakso Use sturdy containers for liquidso Minimise quantities in everyday useo Keep alkanes away from naked flames/sparkso Erect warning signso Don’t handle liquids in confined spaces

Describe the indicators of chemical reactions

- Colour, production of energy (light, heat, noise etc), formation of new substances, process can’t be easily reversed

Identify combustion as an exothermic chemical reaction – releases heat

Outline the changes in molecules during chemical reactions in terms of bond-breaking and bond-making

Explain that energy is required to break bonds and energy is released when bonds are formed

- Breaking bonds in molecules – input energy- Making bonds – release energy

Describe the energy needed to begin a chemical reaction as activation energy

- Minimum amount of energy reactant molecules must possess to form products

Describe the energy profile diagram for both endothermic and exothermic reactions

Explain the relationship between ignition temperature and activation energy

- Ignition temp: of fuel/air mixture is min temp to which mixture must be heated for combustion

- Higher activation energy – higher ignition temp

Identify the sources of pollution which accompany the combustion of organic compounds and explain how these can be avoided

Carbon monoxide/soot

Sulfur dioxide Oxides of nitrogen

Particulates

Source Incomplete combustion – insufficient oxygen

Impurities in fuel, commonly coal

Reaction of O2 and N2 in air from high temp in combustion

Industry/power generation – burning coal and higher BP fractions of crude oil

Avoidance

- Use excess air- Catalyst in exhaust

to convert to CO2 because excess air impossible

- Difficult - Low-sulfur coal- SO2 removal

from effluent gas at power stations

- Locating power stations away from population centres

- Use catalyst to remove from gas effluents from power stations

- Minimised by electrostatic precipitators

Describe the chemical reactions by using full balanced chemical equations to summarise examples of complete and incomplete combustion