Chemistry:

Prelim course:

8.2 – Chemical Earth:

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

- Construct word and balanced formulae equations of chemical reactions as they are encountered

Write up complete equation, and then start by balancing elements that are in compounds first, then the elements that appear afterwards.

Eg: Complete combustion of 1-butene

O2 + C4H8 CO2 + H2O

First balance the Carbons,

O2 + C4H8 4CO2 + H2O

Then Hydrogen’s,

O2 + C4H8 4CO2 + 4H2O

Add up the oxygen’s, (4x2) + (4x1) Ans/2 (Since Oxygen is in the gaseous state)

6O2 + C4H8 4CO2 + 4H2O

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

Element: A substance with only one type of atom composing it, - Carbon

- OxygenCompounds: When two or more elements are CHEMICALLY bonded to one another,

- Carbon dioxide (CO2)- Ammonia (NH3)

Mixtures: A Heterogeneous solution (meaning not evenly spread) of two or more elements, compounds are PHYISCIALLY mixed together.

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

Name Definition Examples of Mixtures Found

Biosphere

Is inhabited by and sustains living matter. The lower part of the atmosphere, the hydrosphere, and the lithosphere to a depth of about 2 kilometres.

Elements = Mostly O2 and N2.

Consists of mainly organic Compounds

such as carbohydrates, protein and fat

Other compounds include water

Atmosphere Layer of Gas, 200-300km thick

Elements nitrogen (78%), oxygen

(21%), argon (0.93%) and neon. ANON

Compounds=Water,Carbon

Dioxide/Monoxide and Nitrogen exist.

Mixture = Air

HydrosphereAll bodies of water found on the Earth

Dissolved O2 and N2

Mostly compound water

Salt water is a mixture of the

compounds water and sodium chloride.

Lithosphere The lithosphere is the outer layer of the Earth to a depth of 17km which includes crust and upper layer of mantle.

Sand is a mixture containing silica

(silicon dioxide) and other metallic

(such as titanium) and non-metallic

compounds as well as ground up shells

and dirt.

Mineral ores which are oxide,

carbonate, sulphate and sulphide

compounds of metals such as iron.

Crude oil and natural gas which are both

mixtures of hydrocarbon (hydrogen and

carbon containing) compounds.

Free elements are rare but can be found,

e.g. silver, platinum and gold

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

- Solids of different sizes- Through sieving (the larger particles remain on top as they cannot pass through the holes)

- Solids and liquids- Through Filtration (the liquid passes through the filter paper, but the solid remains

a finer former of sieving)

- dissolved solids in liquids- Evaporation to remove the liquid completely as liquids have a lower BP than solids

NB: THIS ONLY WORKS FOR WHEN THE LIQUID IS NOT NEEDED- Distillation works on the same basis of boiling points; however the liquid is

evaporated and then condensed.

- Liquids- Distillation

- This utilises the Boiling points of the elements in the mixture with the lowest boiling the earliest. However if they are too close then it needs to be done with a fractionating column.

- Separating funnel- This utilises the density of the liquids, allowing one to be filtered out from

the bottom.

- Gases- Cryogenic distillation

-The gases are cooled until it is completely a liquid and then slowly heated with each gas going up the tube at different times. This utilises the boiling points much like normal distillation.

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

Gravimetric analysis = the composition of a substance in the complete mixture,

This helps in getting the exact amount of chemicals in things such as medicine, and the percentage of impurities in goods such as iron in bronze.

- Identify IUPAC names for carbon compounds as they are encountered.

Prefix Number of CarbonsMeth 1Eth 2Prop 3Bute 4Pent 5Hex 6Hept 7Oct 8Non 9Dec 10

Suffix Formula-ane CnH2n+2

-ene CnH2n

-yne CnH2n-2

2) Although most elements are found in combinations on Earth, some elements are found uncombined

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

The more reactive an element is, the less likely it is going to be found as an uncombined element, this can be shown by gold (which is one of the most unreactive elements,) and also by Sodium which is one of the MOST reactive(sodium chloride). Some elements can be found as BOTH an element and a compound, oxygen can be found as O2 and also as water H2O.

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

Physical Properties Metals Non-Metals Semi

ConductorsLustre Usually

lustrousUsually Dull Variable

M.P. and B.P. High (solids at room temp)

Typically Low( gas/liquid at room temp)

High

Density High (as they are solids)

Low(as they are usually gas/liquids)

Variable

Malleable Yes No VariableConductivity(both heat and electricity)

Yes No(except Graphite) Slight

Ductile Yes No Variable- Account for the uses of metals and non-metals in terms of their

physical properties

MetalsCopper: Highly conductive, extremely ductile and malleable. Used for circuits.Gold: Extremely lustrous, malleable. Used for jewellery.

Non MetalsCarbon (graphite): Extremely brittle. Used for lead pencils.Carbon (diamond): Extremely hard (covalent network lattice). Used for cutting and jewellery.

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

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

All matter is constantly moving in variational movements (small vibrations) whilst gas particles move in both variational and translational movements. This is called “the kinetic particle theory”. Because of this constant movement it means that the particles are going to be constantly hitting one another meaning that there is a possibility for a reaction. A reaction will only occur if there is a productive collision. A productive collision will only occur when there is both the right speed and orientation of both the atoms when they collide.

- Describe qualitatively the energy levels of electrons in atoms

There are 4 Energy Levels, K, L, M, and N. Each represents a different number of maximum atoms in a shell.

Energy Level

Maximum number of electrons

K 2L 8M 18N 32

- Describe atoms in terms of mass number and atomic number

Mass number = number of protons + neutronsAtomic Number = number of protons

Atomic number 6C12.01 atomic mass

Therefore the number of protons in carbon is 6 and the number of neutrons is 6 (12-6). The number of neutrons equals the number of electrons. Therefore it has 6 protons, 6 neutrons and 6 electrons.

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

Positive Ion (+) – when an element loses an electronNegative Ion (-) - when an element gains an electronMonatomic Ions – Ions made up of elements, Mg2+

Polyatomic Ions – Ions made up of compounds, OH-

- Apply the Periodic Table to predict the ions formed by atoms of metals and non-metals

Group 1 Metals lose 1 electron in ionic reactions and become +1 ions, Group 2 lose 2 electrons and so forth, until you reach group 4 which cannot form ions. Group 5 gains 3 electrons and becomes a -3 ion, whilst group 6 gains 2 forming a -2 ion. Group 8 cannot form ions as it has full shells and is stable.

Cations = positive ions (groups <4)Anions= negative ions (groups >4)

- apply Lewis electron dot structures to:- The formation of ions

Draw it in brackets with the charge on the top right corner.Draw only the outer shells

How to draw Lewis dot structures:1) Count how many valence electrons in outer shells of all atoms2) How many are needed3) 2)-1) = number of bonds

- the electron sharing in some simple moleculesCovalent bonds are shown by drawing a circle around the pair of bonding electrons.

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

Ionic compounds form when there is a perfect balance of ions O 2- + Mg 2+ to form MgO.

- Describe molecules as particles which can move independently of each other

All molecules move on their own, due to the momentum that they carry and the Brownian motion that occurs (as seen in the gaseous state).

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

Molecule: The smallest unit of a substance that keeps all of the physical and chemical properties of that substance, it can consist of one atom or two or more atoms bonded together.

Monatomic: Molecules made up of one atom.Polyatomic: Molecules made up of more than one atom.

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

Covalent molecules are made up of only non-metals. This is because the non-metals have 4 or more electrons. E.g. hydrogen – contains one electron. Its shell needs two electrons to be complete. When two hydrogen atoms get close enough, their shells overlap. They share their single electrons, now both atoms have 2 electrons and are stable.

- Construct formulae for compounds formed from:- Ions

Mg2+ + SO42- MgSO4

- atoms sharing electronsN2 + 2O2 2NO2

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

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

A Physical change is one where there is a change in state, colour, size etc… This process can be undone by applying the opposite process to it. For example when water boils it turns into a gas, this gas can be cooled back down into its liquid state. A chemical change relies on the realigning of the atoms with bonds being broken and formed. This usually means that if the reverse process is applied the change will not be undone. If an egg is boiled, the egg cannot be unboiled. Putting bread in a toaster cannot be undone likewise. A Chemical reaction: Rearrangements in the reactant molecules, hence new substance are formed.

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

Boiling water is an example of a physical change in water; this is because no new products are created. The only difference is that there is energy added to the water meaning that it has changed state. This can be undone by absorbing the energy in the water (cooling it down). Electrolysis is the process which SEPERATES water into its 2 components, hydrogen and oxygen. This can be given by the equation 2H2O O2 + 2H2. This shows that 2 new substances have been formed (oxygen and hydrogen meaning that the process has been a chemical change.)

- 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

Type of Energy Industrial Example Everyday ExampleHeat Decomposition of

limestone to form limeDecomposition of baking soda to form carbon dioxide in baking

Light Decomposition of silver bromide in photographic paper

Production of sugars and oxygen during photosynthesis

Electrical Production of aluminium through electrolysis

Synthesis of nitrogen oxide by lightning strikes

- 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.

The amount of energy required to break a bond depends on the intermolecular forces found in the substance. The energy required is used to pull the electrons apart and for that reason in a covalent bond they are much stronger.

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

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

Substance Chemical Properties Physical Properties (at 25*C)Sodium chloride Does not burn, no reaction

with water and hydrogenWhite crystals, soluble in water, does not conduct electricity as a solid, does conduct electricity as a liquid

Sodium Burns in oxygen, violent reactions with water and hydrogen

Soft silvery metal, conducts heat and electricity as a solid/liquid

Chlorine Burns in air, reaction with water, violent reaction with hydrogen

Green gas, does not conduct electricity at all

From this table you can see that all elements and compounds have their own specific traits.

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

Physical Property Ionic Covalent molecular

Network covalent

Example Salt(NaCl) Water (H20) Sand(SiO2)Physical state Solids Variable SolidsAppearance Powder/crystals Dull if solid Shiny Colour Variable Variable SilveryDensity Medium Low to medium MediumHardness Hard/brittle Varies, but

generally softHard/brittle

Structure Crystalline Shapeless CrystallineSolubility in Water All Slightly soluble InsolubleElectrical conductivity of solutions

Good Bad n/a

Thermal conductivity

Poor Poor Good

Melting point High Generally low High

That mean’s is a substance is a conductor in a molten state, soluble in water it is a ionic compound. If slightly soluble, dull in appearance it is most likely a covalent molecular structure. A Network Covalent substance is insoluble in water and is a solid state, what separates it from the others is its thermal conductivity, as it is in a solid state and the other forms do not have free electrons.

- Distinguish between metallic, ionic and covalent bondsIonic bonds – Form between a Metal and a non metal. The non-metal receives electrons from the metal.

Na + Cl NaCl

Covalent bonding – This occurs when the two electrons share their joint electrons to complete their outer shell, this can be seen with most gases.

O + O O2

Metallic bonding – This is the same as covalent bonding, however instead of the electrons being shared with its immediate neighbours it is shared by ALL of the atoms. This is why metallic bonded compounds can conduct electricity.

This occurs in a piece of metal, so equations aren’t necessary.

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

Metal’s are composed of Cations (positive ions) and are arranged in a repeating lattice structure. For this reason the substance is a crystal. The metallic bonding that occurs means that there are delocalised electrons which are known as “a sea of electrons”.

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

Ionic compounds are made up of both positive and negative ions, because of this each Cation (+) is surrounded by Anions (-) and so forth, this creates a 3-D lattice of ions.

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

Empirical formula: The ratio in which the elements are divided in the compound.

Ionic compounds are macromolecular lattices. This means that there are millions of ions, however due to simplicity we use the empirical formula or the ratio that these elements appear in the compound.

- Identify common elements that exist as molecules or as covalent lattices

Diatomic elements: Oxygen, Fluorine, IodineTetrahedral Covalent Lattices: Carbon (diamond), Silicon, GermaniumHexagonal Lattices: Carbon (Graphite), Boron

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

Example Conductivity Reason Hardness ReasonIonic Sodium

Chloride(NaCl)

High(when molten/dissolved)

When molten the electrons are free to move around, however when

Hard, The Strong bonds between the cations and Anions mean that very strong bonds have been

it is not the electrons are in a fixed position

formed.

Covalent Molecular

Water(H2O)

Low No delocalised Electrons

Soft, There are weak bonds between the atoms.

Covalent Lattice

Silicon Dioxide,(SiO2)

Low No delocalised Electrons

Hard/Very brittle

The intermolecular forces are extremely strong and they are closely packed meaning that the substance is likely to shatter and not be malleable.

8.3 – Metals

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

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

Metals have been used throughout the ages.

Gold: Has been used for jewellery and coinage, due to its lustre and rarity. It has also been used in circuits for its high conductivity.

Silver: Has been used for Jewellery, due to its malleability and lustre.

Bronze: Used for jewellery, wiring and cooking utensils. This is because it has a high shine, and high conductivity.

Iron: Used for buildings. Iron is very strong, and malleable (at high heats)

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

Alloy: A homogenous mixture of 2 or more elements, with at least one element being a metal.Alloy Made up of Uses PropertiesIndustrial Steel

Iron, carbon Building Extremely strong and hard, cheap

Brass Copper, Zinc Instruments, coins, decorative

Very Malleable, cheap, non corrosive

Lead Solder 60% Tin, 40% Lead

Electrical circuits, joining metal piping

High conductivity, low M.P. ,soft

Stainless Steel

Iron, Nickel Cutlery Non corrosive, high M.P., hard, strong

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

Energy input is required to break the bonds that are created when the metal reacts with another substance. For example it is very hard to find pure aluminium in the environment, but there is a lot of aluminium oxide. To separate the two, energy must be put in to separate the oxygen from the aluminium.

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

200 years ago, technology was a lot less sophisticated than what it is today. This means that they would not have been able to produce such high amounts of energy, to help separate metals. As metals are stronger and stronger bonded, more energy is required meaning that it is less likely that there was enough technology for the minimum amount of energy to be produced.

The Bronze alloy is relatively easier to produce (through heating copper and tin) than extracting iron from its ore (puddling a molten mixture of iron ore/slag Therefore more metals and alloys were/are produced today due to the increase in quality and quantity of technological developments and scientific understanding. There are also sophisticated methods of extracting ores, such as extracting titanium, which is done by reacting titanium tetrachloride with sodium, inside a heated steel bomb.

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

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

Metals reacting with dilute acid

Acid + Metal Hydrogen + Salt2HCl (aq) + 2Na(s) H2 (Gas) + 2NaCl (aq)

Changes observed-bubbles forming (due to hydrogen gas)- Sodium would “disappear” (it dissolves in the solution)-Colour of solution may change

Notes:Only works on the outside of the metalMetal Neutralises Acid

Metals reacting with water

Water + Metal metal hydroxide + hydrogen2H2O + 2Na 2NaOH + H2

Water is more stable than acid, therefore less metals react with it.

Metals reacting with oxygen

Metal + Oxygen Metal OxideMg + O2 MgO2

Oxygen is very stable, so very rarely happensThis is known as rust, a form of combustion.

- 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

The more violent the reaction, the more reactive and thus the higher the position of the metal in the electrochemical seriesThe degree of reaction with oxygen can be used to identify the most reactive metals (less reactive metals do not react)Metals of moderate reactivity can be determined by their reactivity with water (less reactive metals do not react)Metals that are relatively unreactive can be determined by their reactivity with dilute acids (less reactive metals do not react)

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

Acid molecules break up when they react with Metals; this means that they are Anions. The metals begin to react with them thus sharing their electrons.

- 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

Lithium: used in pace makers, because it is extremely reactive, meaning that electrons can pass through it easily.Magnesium: used in fireworks, it is highly reactive and when burnt it creates a large amount of light energy.Titanium: Used in artificial bones, it is very unreactive and non corrosive. This means that it is not going to deteriorate in the body.

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

Reactivity increases as you go down a group, and as you move towards the left side of the periodic table. Therefore the most reactive element is Francium which is so reactive that it reacts with the water vapour in the air.

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

The lower the Ionisation energy is the higher the reactivity of the element is. This is because it means there is lower activation energy required, meaning there is more chance of the element reacting.

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

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

The most up to date model of the atom has a positively charged nucleus composed of at least one proton and (with one exception) at least one neutron. Surrounding the nucleus are volumes of space in which there is a high chance of finding one or more electrons. The number of positively charged protons in the nucleus is exactly balanced by the number of negatively charged electrons, giving the atom an overall neutral electric charge

- 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

Empedocles stated all things were made of 4substances – Earth, wind, water and fireAristotle said all matter was made up of basic material that assumed different forms1789 Antoine Lavoisier published a table of 33 known elements.1829 Johann Dobereiner suggested triads1862 Alexander de Chancourtois developed a helix screw1864 John Newlands found that they varied periodically according to atomic mass1869 Lothar Meyer Developed a type of periodic table that was arranged according to atomic

weight1869 Dmitri Mendeleev made a similar periodic table

- Explain the relationship between the position of elements in the Periodic Table,- Electrical conductivity

From left to right decreasesIn groups 1-3 electrical conductivity decreases down the groupIn the rest it increases.- Ionisation energyGoing left to right it increasesGoing down a group it decreases- Atomic radiusDecreases as you go left to rightIncreases as you go down- Melting point & Boiling PointIncreases and then decrease across the periodsVARY down a group- Combining power (valency)Going across a period it variesGoing down it is the same- Electro-negativityIncreases as you go left to right- ReactivityVaries as you go left to right Increases (for metals) and decreases for non metals

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

- Define the mole as the number of atoms in exactly 12g of carbon-12 Mole: deals with the number of particles in a substance. It is the amount of ANY substance that is equal to the number of particles as there are atoms in 12g of the Carbon-12The number of particles in one mole of any substance is 6.022x1023.Eg. The number of particles in one mole of helium is 1 x 6.022x1023 = 6.022x1023

particles.- Compare mass changes in samples of metals when they combine

with oxygenWhen metals are reacted with oxygen they form an oxide, which has a higher molecular mass meaning that they have gained some mass. However not all metals will react with oxygen at a fast enough rate to be recorded.

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

Gay Lussac discovered the concept of all gasses react in a whole number ratio. “When gases combine during chemical reactions, they do so in volumes those are always small whole number ratios” Dalton believed that this was because the gas atoms split which was then disproved by Avogadro when he solved the issue.

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

Avogadro’s law states that equal volumes of gas, at the same temperature and pressure, will contain the exact same amount of particles, regardless of their physical and chemical properties.

- Distinguish between empirical formulae and molecular formulae

Empirical formula: The common ratio that can be found in the moleculeMolecular formula: The actual ratio in which the particles are found in the molecule

Eg. C2H8 – Ethane CH4 – empirical Formula (the ratio cannot get any simpler) C2H8 – Molecular Formula (The ratio that the particles in the molecule)

5. The relative abundance and ease of extraction of metals influences their value and breadth of use in the community

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

Mineral: A naturally occurring substance which has been formed through geological processes and has characteristics of a chemical compositionOre: An economically viable rock which contains minerals.

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

Prices of common metals are determined by their abundance and cost of production. This means that if it is very hard to find a certain metal it will raise in price, an example would be platinum. The relative cost of production raises the price of the mineral as the companies want to make a profit. An example would be titanium which is extremely expensive to extract thus raising its price. Ease of transport, is classified under relative costs of production ( so if the ore is in the middle of the desert it will raise costs).

- Explain why ores are non-renewable resourcesA renewable resource –A resource replenished as fast as it is being used.

This means that when an ore is extracted it is not replenished for 1000’s of years so therefore it is not a renewable resource.

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

Copper ore example = copper carbonate1. Copper carbonate reacts with sulphuric acid – CuCO3 (s) + H2SO4 CuSO4 (aq) + H2O (l) + CO2 (g)

2. Copper sulphate is electrolysed (decomposed) and copper is produced at the cathode – (at cathode) Cu2+ (aq) + 2e- Cu (s). This copper is 99.99% pure

- Recount the steps taken to recycle aluminium

1. Scraps taken to recycling plant2. Scraps separated, checked and sorted. 3. Composition/value determined (and further processing occurs if need be). 3. Aluminium transferred to furnace. Heated up to 500*C to produce molten element.4. Aluminium cools, and then it is cast, made into thin sheets. 5. Sheets travel to commercial factories. Sheets are made into beverage cans

1) Recycle2) Sorted3) Heated4) Cast5) Rolled6) Moulded

8.4 –Water:

1. Water is distributed on Earth as a solid, liquid and gas

- Define the terms solute, solvent and solution

Solute: The substance dissolved (usually solid)Solvent: The substance in which the solute is place in (usually liquid)Solution: a Homogeneous mixture

- Identify the importance of water as a solvent

Water is an important solvent because many organisms rely on the minerals which are dissolved in it. Plants gather their nutrients from the water and it is also important as a disposal of waste (such as urea).

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

Sphere Description of Sphere

State of Water

Abundance of Water

% of Earth’s water

Distribution

Lithosphere The crust of the earth(50~200km Deep)

Liquid, solid

<10% 0.6% Found as ground water and ice(on mountain tops)

Hydrosphere All water ON the earths surface

Liquid, solid

>95% >99% In the oceans, glaciers

Atmosphere The air surrounding the earth

Gas, Liquid, solid

0.5%-5% 0.0001% Found as rain, water vapour and hail

Biosphere The area in which living animals inhabit

Gas, Liquid, solid

60-90% 0.0001% Within organisms, in habitats( such as lakes, water vapour and glaciers)

- 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 metabolismBecause water is a good solvent many reactions take place in it, so that means cells are able to complete complex reactions in the medium of water. Water is used in one of the most fundamental reactions of life. Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2

- A habitat in which temperature extremes are less than nearby terrestrial habitatsWater has a High Heat Capacity meaning that it is able to absorb large amounts of heat before increasing in temperature. This means that aquatic life experience less temperature changes over the day allowing life to be able to grow better. - An agent of weathering of rocks both as liquid and solidWater in both liquid and ice states can break rocks down physically and chemically. This is called Weathering. Water can dissolve some of the minerals on the surface of the rock and carry them away. This is known as dissolution. Another form of physical erosion is Erosion, this is when water gathers up in the cracks of rocks, and when frozen expands. This means that the rock splits.- A natural resource for humans and other organismsWater is a versatile substance used for recreation, irrigation, electricity generation and drinking.

2. The wide distribution and importance of water on Earth is a consequence of its molecular structure and hydrogen bonding

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

Arrange bonded atoms around central atom.Count valence shell electrons and determine the number of bonds each atoms forms.Assign bond pairs around the central atom.Assign lone pairs to central atom.Assign lone pairs to peripheral atoms.

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

Ammonia is a tetrahedral shape with a bond angle of 107.3. There is an orbital occupied by a lone pair of valence electrons which repels the three bonding electron pairs. In both water and hydrogen sulphide, there are two pairs of unshared electron pairs (lone pairs). Thus the repulsion is greater and bond angle smaller at 104*.Hydrogen sulphide has the weakest intermolecular forces since the electro negativities of sulphur and hydrogen are similar. Water has two pairs of lone pairs that are regions of negative charge whereas ammonia only has one. Since the intermolecular forces are weaker in ammonia than the melting/boiling point of water is the highest (more heat energy is required to break the forces in the water).

- Describe hydrogen bonding between moleculesHydrogen bonding occurs between a hydrogen, and oxygen, fluorine and nitrogen. This is due to the extreme electro negativity difference. Hydrogen bonds are extremely strong.

- Identify the water molecule as a polar molecule

A polar molecule is a molecule which has a net dipole. That means that one side of the molecule will have stronger dispersion forces applied to it than another side. This can be seen in water (as seen in diagram).

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

As seen in the diagram polar molecules will have both a positive and a negative end. As in the case of water, there are two positive’s (hydrogen) and one negative (oxygen). These poles are only slightly negative and are not to be confused with ions. The positive end of the water is attracted to the negative end of another water molecule and they become a lot closer.

- Explain the following properties of water in terms of its intermolecular forces:- Surface tensionSurface tension occurs when there is an imbalance of forces in a substance. This can be seen on the surface of water. Because water is a polar molecule it is attracted to the surrounding ones. However, on the surface there are no molecules above it so it is drawn inwards creating a “tight surface”.

- Viscosity

Viscosity is the ability for a liquid to flow. Viscosity is determined by 2 things. Molecular size and complexity, (the larger the molecule the higher its viscosity) and strength of intermolecular forces (The stronger the intermolecular forces the higher the viscosity).Since water is an extremely small molecule, and when compared to other molecules its size the intermolecular forces are high, this means that water is relatively high.-Boiling and melting pointsBoiling and melting points are determined by the intermolecular forces of the molecules. Because water has 2 hydrogen bonds and a relatively high polarity it means that it has a high M.P. and B.P. for its molecular size.

3. Water is an important solvent

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

Soluble ionic compound (sodium chloride): ions attracted to water molecules, bonds between sodium and chloride ions break and move around solution, becoming hydrated (chemically combined with water molecules).Soluble molecular compound (sucrose): when sucrose is added to water electrostatic attractions from between the hydroxyl groups of the outermost molecules of the sucrose crystal and the water molecules that come into contact with them. Partially soluble molecular element or compound (hydrogen chloride): non-polar, forms weak dispersion forces with water. Covalent network substance (silicon dioxide): the component atoms are held together by very strong intramolecular covalent bonds. When water is added the forces that are possible of forming are significantly lower than the forces already present in water and sand. Thus, sand is insoluble in water. A substance with large molecules (cellulose): Covalent bonds between giant cellulose molecules do not break when added to water. It is insoluble in water.

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

Water’s dipole is attracted to many other substances which carry a partial or full electron charge. “Like dissolve like.” If the forces of attraction which can form between the substance and water are stronger the forces for the substance, it dissolves.

4.The concentration of salts in water will vary according to their solubility, and precipitation can occur when the ions of an insoluble salt are in solution together.

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

Compounds that are Soluble

Exceptions Compounds that are insoluble

Exceptions

Group 1 and NH4+

compoundsCarbonates Group 1 and NH4

+ compounds

Nitrates Phosphates Group 1 and NH4+

compounds

Chlorides , Bromides and Iodides

Ag+ Pb+2 Hydroxides Group 1 and NH4+,

Ba+2, Sr+2, Ca+2

Sulphates Ag+, Pb+2, Ba+2, Oxides Group 1 and NH4+,

Sr+2, Ca+2 Ba+2, Sr+2, Ca+2

Common Precipitates:AgClPbSO4

- Identify the dynamic nature of ion movement in a saturated dissolution

Ions break off lattice and go into solution. As more ions become hydrated the rate of dissolving slows down. The rate at which the ions leaving and rejoining the crystalline lattice increases. This rate is constantly changing (dynamic). MX (s) <-> M+ (aq) + X- (aq)- Describe the morality of a solution as the number of moles of

solute per litre of solution using: c = n/vNumber of moles of solute/ volume of solution (mL)

- Explain why different measurements of concentration are important

Different measures of concentration are important for the strength of drugs, commercial labelling of products.

5.Water has a higher heat capacity than many other liquids.

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

Heat Capacity is how many Degrees it takes for a substance to increase by one Degree.

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

Water C = 4.18Ethanol: 2.44Petrol: 2.22Hexane: 2.26Propenol: 2.17

- Explain and use the equation ΔH = -mC ΔT

ΔH= Change in enthalpy (measured in J)M = mass (measured in Kg)C= Specific Heat Capacity (Measured in J.kg-1.K-1)ΔT= Change in Temperature (Measured in K)

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

Using the Change in Enthalpy we can find how many degrees a substance has increased by. This can then tell you how many joules the reaction has created.

- Describe dissolutions which release heat as exothermic and give examples

Exothermic reactions RELEASE energy into its surroundings this is because the bonds broken do not need to use up all its energy to create the new bonds and an example would be sodium hydroxide and sulphuric acid being reacted together.

- Describe dissolutions which absorb heat as endothermic and give examples

Endothermic reactions ABSORB heat, this is because the bonds that are broken are not as strong as the bonds that are created, this means that energy is needed from the environment to help the reaction work. An example of this would be ammonium nitrate and potassium chloride.

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

Because of the high heat capacity of water, the oceans are able to stay at a relatively stable temperature, encouraging life to grow, with tout the worry of drastic habitat changes. If water had a very low heat capacity it would mean that it would be very hard for human’s to survive as most cooling methods involve water. It would lead to more rainfall (water cycle) and more flooding.

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

Thermal pollution is temperature in natural water bodies caused by human influence. This usually means a change in temperature of approximately 2-5 degrees. When this happens it results in a decreased solubility of oxygen, disruption of spawning and kill organisms that cannot live in the new temperature. However some positives is that some places thrive with the new increase in temperature, one case is the Manatee which moves towards power plant sites during winter.

8.5 –Energy:

1. Living organisms make compounds which are important sources of energy

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

Photosynthesis is one of the most important chemical reactions. This is because this is the only way that light energy is converted into chemical energy and stored as glucose. The formula for photosynthesis is represented by 6CO2 + 6H2O C6H12O6 + 6O2. This formula shows that photosynthesis is endothermic and also shows that it forms a Carbohydrate.

- 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

Photosynthesis is used to change light energy (from the sun) into chemical potential energy (carbohydrates). Photosynthesis uses the sun’s energy to change carbon dioxide and water to glucose and oxygen. Using high energy carbohydrates also means that you are able to store energy much more efficiently. It also means that it is going to be a long term fuel storage system.

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

The three main fossil fuels are coal, petroleum and natural gas. Coal is made up of plants that have been buried in swamps and compressed into pure carbon. Petroleum and Natural gas are both originated from marine plankton and bacteria, which is then heated under high temperatures and pressure. Fossil fuels contain large amounts of chemical energy. This means that all the energy found in fossil fuels is derived from plants. Plants get there energy from the sun thus all energy in fossil fuels is derived from the sun.

2. There is a wide variety of carbon compounds.

- Identify the position of carbon in the Periodic Table and describe its electron configuration

Carbon is the 6th element on the periodic table. It is in Group 4 and Period 2. Its electron configuration is 2, 4.

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

Allotrope: a structural variant of an element. It has different bonding patterns which lead to different physical and chemical properties.

Diamond 3-D covalent latticeHardest known substanceHigh M.P., B.P.InsolubleDoes not conduct electricity

Graphite High M.P., B.P.

Conducts ElectricitySoftLayers (held by dispersion forces)

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

Hydrocarbons are a great example. Alkanes form carbon-carbon single bonds, alkenes form carbon-carbon double bonds and alkynes form carbon-carbon triple bonds.

- 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

Carbon atoms have four valence electrons capable of forming four covalent bonds and can form single, double or triple bonds with itself. Carbon-carbon bonds are strong and not easily broken. There are numerous compounds containing carbon-carbon bonds e.g. hydrocarbons, allotropes of carbon. There are several million organic: carbon-based molecules have been discovered.

- 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)

The M.P. and boiling points of hydrocarbons goes up as there overall mass increases. All forms of hydrocarbons except the –ynes are non polar. Alkanes have a higher boiling point than Alkenes (this is because of the higher Molar mass). Alkenes are more reactive because they contain a double bond.

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

Because Alkanes are extremely flammable it is suggested that they should be kept well away from naked flames or cigarette butts. It is also recommended that they are kept under high pressure (to remove the problems of flash point).4. Combustion provides another opportunity to examine the conditions under which chemical reactions occur

- Describe the indicators of chemical reactionsIrreversible change in appearanceEnergy produced or absorbedFormation of a gasFormation of a precipitateDisplacement of a metal from its compound

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

The breaking of chemical bonds is an endothermic process. The amount of energy required to break all the bonds is known as the activation energy.

- Identify combustion as an exothermic chemical reactionCombustion = substances burns in oxygen. The energy produced is much greater than the activation energy.

- Explain the relationship between ignition temperature and activation energy

Activation energy: minimum energy required for colliding particles to react.Ignition temperature: minimum temperature required for a fuel/air mixture to spontaneously ignite.Reactions that have large activation energy tend to not spontaneously react.

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

Complete combustion produces both carbon dioxide and water vapour. CO2 is a greenhouse gas. Incomplete combustion produces carbon monoxide, carbon dioxide, particulate carbon and water vapour. CO is harmful to humans and the environment. When hydrocarbon fuels burn they produce many pollutants, some of which assist in the formation of photochemical smog. Catalytic converters in car exhaust systems break down CO and hydrocarbons into CO2 and H2O.

5. The rate of energy release is affected by factors such as types of reactants

- Describe combustion in terms of slow, spontaneous and explosive reactions and explain the conditions under which these occur

Slow: not enough air/oxygen to combust substance quickly. E.g. rust. Spontaneous: A slow build up to the combustion of a substance. E.g. Liquid ethanol. Explosive: fast, uncontrolled combustion reactions. E.g. Methane leaking from a gas tap.

- Explain the importance of collisions between reacting particles as criterion for determining reaction rates

For a reaction to occur, particles must collide. The more successful collisions i.e. where a chemical reaction takes place, the faster the rate of chemical reaction. The rate of reaction is directly proportional to the concentration of reactant particles. Average energy of collision and orientation of collision are two important factors in the rate of chemical reactions.

- Describe the role of catalysts in chemical reactions, using a named industrial catalyst as an example

Vanadium (V) oxide. It is a very important chemical, used as a catalyst in the manufacture of sulphuric acid, which is produced in massive quantities around the world for various chemical and industrial purposes.

- Explain the relationship between temperature and the kinetic energy of particles

When the particles get hotter, it means that they move faster, increasing the possibility of a productive collision.

- Explain the role of catalysts in changing the activation energy and hence the rate of chemical reaction

Catalysts are used to lower the activation rate. This means that it is more likely of chemical reactions to occur. Catalysts lower the activation energy by increasing the number of particles that collide with favourable orientation, attract reactant particles to its surface thus increasing reactant concentration, increase the reactivity of reactant molecules and provide a series of low activation energy reactions to form products.