Chemical Earth - Engaging with the Syllabus (Prelims)

MODULE 1: THE CHEMICAL EARTH
3.1.1: Elements in Earth 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
Matter: anything that has mass and occupies space. Exists in three different states: solid (s), liquid (l) and gas (g)
The Particle Theory: “All matter is made up of small, indivisible particles called atoms that are continuously moving” | Solid | Liquid | Gas | Particle Position | Closely packed.Vibrations only. | Less closely packed.Vibrations and translations. | Widely spread. Rapid translation. | Volume | Definite volume | Definite volume | Takes the shape and volume of container. | Shape | Definite shape | Takes the shape of the container. | | Compressibility | Negligible compressibility. | Negligible compressibility | High compressibility. |

1.1.2 The living and non-living components of the earth contain mixtures * Identify the difference between elements, compounds and mixtures in terms of particle theory
The Particle Theory: “All matter is made up of small, indivisible particles called atoms that are continuously moving”
Elements: simplest and pure substance consisting of same type of atom. Cannot be decomposed by ordinary physical and chemical means
E.g.H2,O2 Mg, C, Zn, Na.

Compounds: pure substance consisting of two or more atoms of different types of elements chemically combined in a fixed ratio. Can only be decomposed by chemical means
E.g. H2O, CO2, NaCl, C6H12O6.

Mixtures: impure substance consisting of two or more substances in a variable proportion. Either homogenous or heterogeneous * Homogenous: substance with uniform composition and properties throughout. * 1 phase * Uniform physical appearance
E.g. Salt water (H2O andNaCl) - Salt is soluble – dissolve in water – uniform appearance. * Heterogeneous: substance with variable composition and properties throughout. * More than 1 phase * Non-uniform physical appearance
E.g. Sand and water - Sand is not soluble – won’t dissolve in water – 2 phases doesn’t give uniform appearance.

Difference between pure substances and mixtures | Pure substances (Element/Compound) | Mixture | Cannot be separated into 2 or more substance by physical means | Can be separated into 2 or more substances using their physical properties | Homogenous | Homogenous or Heterogeneous | Has a fixed composition | Has variable composition with variable amounts of each pure substance | Has constant property | Displays the characteristics of each component making up the mixture. |

1.1.3: The living and non-living components of the earth contain mixtures * Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds
Lithosphere:
* The earth’s crust that contains many different types of minerals * A mixture of these minerals sedimental with sand, rock and soil Element | Abundance in crust | Oxygen | 46.6 | Silicon | 27.7 | Aluminium | 8.2 | Iron | 5 |

Hydrosphere: * Water is the most abundant compound, therefore, oxygen and hydrogen is the most abundant element * Sea water consists of many dissolved minerals such as salt
Biosphere:
* Region where living organisms are found * Most living things are composed of cells which contain complex carbon compounds, such as carbohydrates, fats and proteins Element | Abundance | Oxygen | 60 | Carbon | 21 | Hydrogen | 11 |

Atmosphere: * Layer of a mixture of gases above the earth’s surface * Nitrogen and oxygen are the most abundant gases in the atmosphere Gas | Composition | Nitrogen | 75.3 | Oxygen | 23.1 | Argon | 1.3 |
2.1.1: 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
Elements: simplest and pure substance consisting of same type of atom. Usually exist as compounds. * The more reactive an element is, the less likely it is to exist in nature itself – because it would be more likely to react with another element. * Monatomic: having one atom in the molecule, found uncombined in nature because they don’t react (inert).
E.g. Noble gases – He, Ne, Ar * Diatomic: having two atoms in the molecule, found in nature bonded to atom of same element.
E.g. Hydrogen (H2), Oxygen (O2), Nitrogen (N2)

2.1.2: Although most elements are found in combinations on Earth, some elements are found uncombined * Classify elements as metals, non-metals and semi-metals according to their physical properties Property | Metals | Non-metals | Semi-metals | Elements | Iron (Fe), Silver (Ag), Gold (Au), Aluminium (Al), Zinc (Zn), Copper (Cu) | Carbon (C), Oxygen, (O), Nitrogen (N), Helium (He), Chlorine (Cl) | Boron (B), Silicon (Si), Germanium (Gs), Arsenic (As) | Melting point | Usually high | Usually low | High | Boiling point | Usually high | Usually low | Usually high | Electrical conductivity | High | Very low | Low | Heat conductivity | High | Very low | Low | Appearance | Lustrous | Usually not lustrous / Dull | Variable | Malleability and ductility | Malleable and ductile | Brittle | Ductile and malleable |

2.1.3: Although most elements are found in combinations on earth, some elements are found uncombined * Account for the uses of metals and non-metals in terms of their physical properties
Metals:
Physical property | Use | Relatively high densities (except for lithium, sodium and potassium which are less dense than water) | Useful in being a strong material used for manufacturing and infrastructure | Good conductors of heat and electricity | Used to create electricity | Malleable (can be beaten into sheets) and ductile (can be drawn into wires) | Can be moulded to fit its purpose in terms of manufacturing products, such as light stand or a swing set. | Relatively high melting points (except for mercury and gallium which have quite low melting points | Reliable material for infrastructure as it won’t break easily | E.g. Aluminium widely used for utensils, drink cans, saucepans, cooking foils, building construction as roofing and window frames, and in boat construction – relating to aluminium’s thermal conductivity, malleability and attractive lustre. |
Non-metals:
Physical property | Use | Usually not lustrous | Can be used to make objects that are not meant to be shiny, such as tables (Wood) | Poor conductors of heat and electricity (Except for carbon in the form of graphite) | Makes good insulators, can be used to make protective gear against heat and electricity, such as gloves | Not malleable or ductile, often brittle | Can be used to manufacture products that are easy to open/break, such as cardboard boxes | E.g. Carbon (graphite) – used in lead pencils and as a lubricant because of its softness and layer structure, allowing layers of atoms to slide over each other - Also used in electrodes in batteries and electrolytic processes because of its electrical conductivity |
2.2.1 Although most element are found in combinations on Earth, some element are found uncombined * 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
2.2.2: Although most elements are found in combinations on Earth, some elements are found uncombined * Analyse information from secondary sources to distinguish the physical properties of metals and non-metals Property | Metals | Non-metals | Semi-metals | Melting point | Usually high | Usually low | High | Boiling point | Usually high | Usually low | Usually high | Electrical conductivity | High | Very low | Low | Heat conductivity | High | Very low | Low | Appearance | Lustrous | Usually not lustrous / Dull | Variable | Malleability and ductility | Malleable and ductile | Brittle | Ductile and malleable |

Metals | Non-metals | Malleable | Not malleable | Ductile | Not ductile | Not brittle | Generally brittle | Strong and have high tensile strengths | Not strong with low tensile strength | Good conductors of heat and electricity | Bad conductors of heat and electricity (except graphite) | Good lustre | Poor lustre | Solids at room temperature (except mercury) | Solids, liquids or gaseous at room temperature | High melting points (except sodium and potassium) | Solid non-metals have low melting points | Generally high densities | Generally low densities |

Metals are usually dense, strong and not brittle with high melting points (except sodium and potassium). At room temperature metal are solids (except for mercury which is a liquid). It is shiny and lustre and also malleable and ductile. They also make good conductors of heat and electricity.
Non-metals are usually light, brittle and not strong with low melting points. They can exist in any state (solid, liquid or gas) at room temperature. They aren’t malleable and ductile; they aren’t shiny and make bad conductors of heat and electricity.
2.2.3 Although most elements are found in combinations on earth, some elements are found uncombined * 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˚C and normal atmospheric pressure

5.1.1: 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 | Elements | Compounds | Mixtures | Definition | Substance made of 1 type of atom | Substance made up of 1 type of molecule OR made up of 2 or more elements chemically bonded together | Substance made up of 2 or more different elements or compounds | Chemical property | Cannot be separate into 2 or more substance by physical means | Cannot be separate into 2 or more substance by physical means | Can be separated into 2 or more substances using their physical properties | Physical property | Homogenous | Homogenous | Homogenous or Heterogeneous | | Has a fixed composition | Has a fixed composition | Has variable composition with variable amounts of each pure substance |
1.1.4: The living and non-living components of the earth contain mixtures * 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
Solids of different sizes – based on particle size: * Sieving - is the process of separating solid particles of various sizes. The mixture is separated based on their particle size. The mixture is poured onto the sieve, the smaller particles will pass through leaving the larger particles in the sieve.
E.g. Dirt and pebbles - The large pebbles will be left behind as the dirt will pass through the sieve. * Magnetism – is used to separate certain substances (such as iron filings) on their ferromagnetism. These ferromagnetic substances will attach to the magnet and hence becomes separated from the mixture. * Ferromagnetism – the basic magnetic property where a substance is naturally attached to a magnet.

Solids (insoluble) and liquids – based on solubility: * Filtration - is the process where undissolved solid particles are separated from a liquid by passing the mixture through a screen such as a filter paper that is fine enough to collect the particles of the solid. * The liquid that passed through – is the filtrate. * The solid left - is the residue

* Sedimentation - occurs when solid particles are allowed to settle from the mixture (solvent). The two types of sedimentation are: * Decanting - where the mixture is left to settle completely. Gravity will eventually make the heavier, insoluble solid settle to the bottom, leaving a clear solution above. The liquid can be poured out to separate the mixture. * Centrifugation - separates the mixture of chemicals using a fast spinning motion in a machine called a centrifuge; it is much faster than decanting. The outward force from the spinning motion will make the particle settle faster.

Dissolved solids in liquids – based on boiling point/volatilities: * Evaporation - will allow the liquid to evaporate off leaving the solid behind – this occurs because liquids have a lower boiling point than solids. Heat the mixture using a Bunsen burner or a source of heat, let the liquid evaporate leaving the solid behind.

* Distillation - will allow the liquid to evaporate and still be kept, as well as leaving the solid behind. It’s similar to evaporation; however, the liquid will be kept. Connect a condenser column to the head of the tube, when the liquid evaporates, the gas particles will travel through the condenser, returning to its liquid form.

Liquids – immiscible (do not mix with each other), miscible (mix with each other): * Separating immiscible liquids - Immiscible liquids do not mix with each other forming a heterogeneous mixture – a separating funnel can separate the distinct layers of liquid. The liquid with the highest density will sit at the bottom, and the liquid with the lowest density will sit at the top – releasing the tap of the separating funnel will allow the liquid with the highest density to drip out. * Separating miscible liquids - Miscible liquids mix with each other forming homogenous mixture – cannot use separating funnel. * Distillation - Used when the boiling points of liquids have vast differences – both liquids are boiled and the one with a lower boiling point will evaporate and condense back to its quid state through the condenser. * The liquid in the external beaker is called the distillate. * Fractional distillation - Used when the boiling points of liquids have similar boiling points. The arrangement of the fractionating column allows for repeated condensations and vaporisations up the column which effectively distils the mixture.

Gases: * Fractional distillation - the gas will be condensed into its liquid state before being distilled.
E.g. With nitrogen and oxygen gas, the mixture must be cooled down to about -200°C so both gases will condense into liquids. Nitrogen has the lower B.P. N2(g) = -196°C, O2(g) = -183°C * Zeolite sieve - This uses selective adsorption. A particular type of gas will be adsorbed (stick onto) the sieve while the other gases passes through.
E.g. separating oxygen gas from an air mixture
1.1.5: The living and non-living components of the earth contain mixtures * Assess separation techniques for their suitability in separating examples of earth materials, identifying the differences in properties which enable these separations Separation method | Property used in separation | Technique | Filtration | Solubility | Undissolved solid particles are separated from a liquid by passing the mixture through a filter | Sieving | Particle size of solids | The smaller particles will pass through the sieve, leaving unwanted bigger particles in the sieve | Evaporation | Solubility | One of the components of a mixture evaporates more readily | Crystallisation | Solubility | | Distillation | Boiling points (Volatility) (very different boiling points) | Components with different boiling points in a liquid mixture are evaporated by boiling and condensing the mixture | Fractional distillation | Boiling points (Volatility) (similar boiling points) | Components with different boiling points in a liquid mixture are evaporated by boiling and condensing the mixture | Separating funnel (Decantation) | Density of immiscible liquids) | Used to separate immiscible liquids | Magnetic separation | Magnetic properties / Ferromagnetism | Components with different magnetic properties are separated by passing the mixture through a magnetic field | Froth flotation | Difference in density | To separate wanted minerals from unwanted gangue. Wanted minerals float in the froth, unwanted sink into the gangue | Zeolite sieve | Selective adsorption | Used to separate particular gases from the air mixture |
1.2.4: The living and non-living components of the earth contain mixtures * Identify data sources, gather, process and analyse information from secondary sources to identify the industrial separation processes used as a mixture obtained from the biosphere, lithosphere, hydrosphere 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 water from the processes used
1.1.6: The living and non-living components of the earth contain mixtures * Describe situations in which gravimetric analysis supplies useful data for chemists and other scientists
Gravimetric analysis is a method of analysis that involves the measurement of masses (quantitative analysis – how much of each substance is present?) * The percentage composition of a compound can be determined experimentally – for example, information about chemical composition can be determined by decomposing the compound and weighing one or more of the products.
E.g. Water (H20) consists of 11.1% of hydrogen and 88.9% of oxygen. Therefore, 100g sample of water contains 11.1g of hydrogen and 88.9g of oxygen. * Mm(H2) = 2(1.008) = 2.016
Mm(O) = 16.00
Mm(H20) = 2(1.008) +16.00 = 18.016
% Hydrogen =2.01618.016 x 100 = 11.1% % Oxygen = 16.0018.016 x 100 = 88.9%
E.g. A mineral weighing 273kg in total is known to contain the compound, lead (II) chloride (PbCl2). A sample weigh 4g contains 2.1g of PbCl2. Determine:
a) The mass of PbCl2 in the mineral * Mass of PbCl2 = 0.00210.004 x 273
= 143. 325 kg
b) The mass of the lead in the mineral * Mm(Pb) = 207.2
Mm(CL2) = 2(35.45) = 70.9
Mm (PbCl2) = 207.2 + 70.9 = 278.1
% = 207.2278.1 x 100 =74.5 %
∴ m(Pb) in mineral = 207.2278.1 x 143.325 106.785 kg.
E.g. If you were given a solid mixture of sand and salt, how could you determine the percentage of each in the residue?
Sample results * Mass of sample = 3.45g * Mass of sand = 1.27g * Mass of salt = 2.08g
% Sand in sample = mass of sandmass of sample × 100 = 1.273.45 × 100 = 36.8%
% Salt in sample = mass of saltmass of sample × 100 = 2.083.45 × 100 = 60.3%
E.g. A mineral weighing 273kg in total. It is known to contain the compound, lead (II) chloride (PbCl2). A sample weigh 4g contain 2.1g ofPbCl2. Determine:
a) The mass of PbCl2 in the mineral.
Mass of PbCl2 = 0.00210.004 × 100 = 143.325kg
b) The mass of the lead in the mineral.
Mm(Pb) = 207.2
Mm(Cl2) = 2(35.45) = 70.9
Mm(PbCl2) = 207.2 + 70.9 = 278.1 % = 207.2278.1 × 100 ≈ 74.5%
∴ m(Pb) = 207.2278.1 × 143.325 = 106.785kg (3dp)
1.2.2: The living and non-living components of the earth contain mixtures * 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.
1.2.3: The living and non-living components of the earth contain mixtures * Gather first-hand information by carrying out a gravimetric analysis of a mixture to estimate its percentage composition.
3.1.3 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe atoms in terms of mass number and atomic number * Atomic number (Ζ): number of protons of an atom. * Each element has its own unique atomic number. * No two atoms of different elements can have the same atomic number. Thus, they cannot have the same number of protons. * Mass number (A): the sum of the number of protons and neutrons in the nucleus. * In neutral atoms: number if protons = number of electrons.
3.1.2 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe qualitatively the energy levels of electrons in atoms * The electron configuration is the arrangement of electrons around a nucleus. * The 2n2 rule: used to determine the maximum of electrons that occupy each level. * 1st shell (n=1) - 2(1)2 = 2 * 2nd shell (n=2) - 2(2)2 = 8 * 3rd shell (n=3) – 2(3)2 = 18
3.1.4 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe the formation of ions in terms of atoms gaining or loosing electrons * Since electrons are 2000th the mass of a proton or neutron – atoms can gain or lose electrons but not protons or neutrons. * Atoms gain, lose or share electrons in order to gain a full outer shell, to become stable like the noble gases (He, Ne, Ar, Kr etc), which all have 8 electrons in their outer shell. * Octet Rule (Rule of eight):
“Atoms in nature will tend to copy the stable electron configuration of the closest noble gas. Investigations have shown that except helium, all noble gases have 8 electrons in their outermost shell.” * Anion (negatively charged ion) – when an atom gains electron, has a surplus of electrons and become negatively charged. * Cation (positively charged ion) – when an atom loses electrons, has a surplus of protons and is positively charged.
3.1.5 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Apply the Periodic Table to predict the ions formed by atoms of metals and non-metals * Valency is the combining power of the atom, indicating the number of electrons lost or gained by an atom to obtain its stable electron configuration. * It generally indicates the charge of its stable ion.
Note:
* Electrons in the outermost shell = valence electrons * Outermost shell = valence shell
E.g. Magnesium (2,8,2) has 2 valence electrons, Fluorine (2,7) has7 valence electrons.

* Periodic Table Group | I | II | III | IV | V | VI | VII | VIII | Element | Na | Mg | Al | Si | P | S | Cl | Ar | Valency | +1 | +2 | +3 | ±4 | -5 | -6 | -7 | 0 | Electron Configuration | 2,8,1 | 2,8,2 | 2,8,3 | 2,8,4 | 2,8,5 | 2,8,6 | 2,8,7 | 2,8,8 | | Metals: tendency to lose electrons (becoming cations) to achieve a stable electron configuration | | Non-metals: tendency to gain electrons (becoming anions) to achieve a stable electron configuration | |

3.1.6 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Apply Lewis electron dot structures to: * The formation of ions * The electron sharing in some simple molecules * Lewis electron dot diagrams: visual representation of the valence electrons of an element, ion or compound.

Formation of ions

Electron sharing

3.1.7 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe the formation of ionic compounds in terms of the attraction of ions of opposite charge * The bonding of an ionic compound rises from the electrostatic attraction between oppositely charged ion. * Ionic bonds involve atoms losing and gaining electrons, henceforth forming ions, charged atoms. The attraction of opposite charges (electrostatic force) bonds the ions in the ionic compound together.
3.2.2 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Construct ionic equations showing metal and non-metal atoms forming ions.

3.1.8 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe molecules as particles which can move independently of each other * The intermolecular force between molecules is a weak force in comparison to the intramolecular force holding the atoms of the molecule together. This weak force allows the molecule to use the ability to move independently.
3.1.9 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Distinguish between molecules containing one atom (the noble gases) and molecules with more than one atom Diatomic molecules | O2, Cl2, F2, etc. | Triatomic molecules | H2O, CO2, O3, etc. | Tetratomic molecules | PCl3, NH4, H2O2, etc. | * Note:
Only noble gases can exist as monatomic particles (molecules containing one atom.
3.1.10 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Describe the formation of covalent molecules in terms of sharing of electrons * Covalent bonds are attractive forces between atoms that occur because the atoms are sharing one or more pairs of electrons. * The shared pair of electrons orbits the nuclei of both atoms an equal amount of times, hence holding the atoms together and form a covalent compound.
3.1.11 Elements in Earth materials are present mostly as compounds because of interactions at the atomic level * Construct formulae for compounds formed form: * ions * atoms sharing electrons Ions | Sharing electrons | * Na++Cl-→NaCl(s) * Mg2++ O2-→MgO * Ca2++Cl-→CaCl2 * Al3++S2-→Al2S3 | * 2H2++O22-→2H2O * C4++O22-→CO2 * N23++3H2+→2NH3 * H2++2Cl-→2HCl |
1.1.7 The living and non-living components of the Earth contain mixtures * Apply systematic naming of inorganic compounds as they are introduced in the laboratory
Ionic compounds: * Write the name of the metal first (Cation) * Write the beginning of the non-metal * Add “ide” as a suffix
Covalent compounds: * Use the normal element name for the first element and add – ide for the second * The first element is the one which occurs further to the left in the periodic table * If both elements occur in the same group then the one lower down the group is named first * An exception to the above rules is that oxygen is named last in the compounds with chlorine, bromine and iodine * The number of atoms of each type are given by using the prefixes mono, di, tri, tetra, penta, hexa, hepta in front of each part of the name (though more is usually committed from the 1st name element)
1.1.8 The living and non-living components of the Earth contain mixtures * Identify IUPAC names for carbon compounds as they are encountered * IUPAC – International Union of Pure and Applied Chemistry * All livings things are made up largely of compounds of carbon at the molecular level of life. * Carbon atoms can combine covalently with each other and with different elements to form an enormous variety of compounds, such as * Drugs * Synthetic and natural fibres * Plastics * Foods * Fuels * Hydrocarbons: covalent compounds that only contains hydrogen and carbon. * IUPAC naming of straight chain hydrocarbons using chain and suffix * Chain (length of carbon chain) * (1) -> meth- * (2) -> eth- * (3) -> prop- * (4) -> but- * (5) -> pent- * (6) -> hex- * (7) -> hept- * (8) -> oct- * (9) -> non- * (10) -> dec- * Suffix (which family or homogenous series the compound belongs to) * - ane (Alkane) (CH2N+2) * - ene (Alkene) (CH2N) * - yne (Alkyne) (CH2N-2)
5.1.2 The properties of elements and compounds are determined by their bonding and structure * Describe the physical properties used to classify compounds as ionic or covalent molecular or covalent network Physical properties of covalent molecular substances | Physical properties | Explanation | Low MP, BP | Weak intermolecular forces means low amount of energy (heat) required to break the forces apart (reason why most covalent substances are gases). | Poor conductors of electricity in all physical states (S, L, G) | Lack of moving charge carriers or free moving charged particles (e.g. electrons). | Solids are usually soft (i.e. not hard) | Have weak intermolecular forces which are easily overcomed. |

Physical properties of covalent network substances | Physical properties | Explanation | Extremely high MP and BP | Extremely strong covalent bonds between all molecules. | Poor electrical conductors in all states | No free moving charge carriers (held rigidly in the covalent bonds). | Extremely hard and brittle | Strong covalent bonds held rigidly in a tetrahedral fashion. |

Physical properties of ionic compounds | Physical properties | Explanation | High MP and BP | Strong electrostatic attraction between oppositely charged particles. | Poor electrical conductors in solid state but are good electrical conductors in aqueous and molten states | Ions are tightly bound by the strong electrostatic attraction. When ionic bonds are broken, ions become freely moving, allowing a flow of electrons. | Hard and brittle | Distortion usually brings like charges together, causing repulsion. This forces the crystal (lattice) to shatter. |

Physical properties of metallic bonds | Physical properties | Explanation | High MP and BP | Strong metallic bond = more energy (heat) required to break the bond. | Good electrical conductor in all states | Presence of delocalised electrons which are free to move throughout the lattice. | Malleable and ductile | Delocalised electrons means that the structure will not shatter (like ionic crystals). |

5.1.3 The properties of elements and compounds are determined by their bonding and structure * Distinguish between metallic, ionic and covalent bonds Physical properties | Metallic bonds | Ionic molecular | Covalent molecular | Covalent network | Melting point (MP) and boiling point (BP) | High MP and BP- Strong metallic bond = more energy (heat) required to break the bond. | High MP and BP- Strong electrostatic attraction between oppositely charged particles. | Low MP and BP- Weak intermolecular forces means low amount of energy (heat) required to break the forces apart (reason why most covalent substances are gases). | Extremely high MP and BP- Extremely strong covalent bonds between all molecules. | Electrical conductivity | Good electrical conductor in all states- Presence of delocalised electrons which are free to move throughout the lattice. | Poor electrical conductors in solid state but are good electrical conductors in aqueous and molten states- Ions are tightly bound by the strong electrostatic attraction. When ionic bonds are broken, ions become freely moving, allowing a flow of electrons. | Poor conductors of electricity in all physical states (S, L, G)- Lack of moving charge carriers or free moving charged particles (e.g. electrons). | Poor electrical conductors in all states- No free moving charge carriers (held rigidly in the covalent bonds). | Hardness and malleability | Malleable and ductile- Delocalised electrons means that the structure will not shatter (like ionic crystals). | Hard and brittle- Distortion usually brings like charges together, causing repulsion. This forces the crystal (lattice) to shatter. | Solids are usually soft (i.e. not hard)- Have weak intermolecular forces which are easily overcomed. | Extremely hard and brittle- Strong covalent bonds held rigidly in a tetrahedral fashion. | | | | | |
5.1.4 The properties of elements and compounds are determined by their bonding and structure * Describe metals as three-dimensional lattices of ions in a sea of electrons * Metals are made up of metallic bonds which are strong electrostatic forces of attraction between the positive lattice ions and the sea of delocalised electrons. * Metals are formed as the result of positive ions arranged in a three-dimensional lattice with delocalised electrons moving throughout the lattice. The delocalised electrons are lost from the valence shell from each metal atom and belong to the lattice as a whole. The attraction between the positive metal ions and delocalised electrons stabilises the lattice. This attraction is called the metallic bond.

5.1.5 The properties of elements and compounds are determined by their bonding and structure * Describe ionic compounds in terms of repeating three-dimensional lattices of ions * Ionic compounds are made up of ionic bonds which are electrostatic forces of attraction between oppositely charged ions. These compounds have a regular 3D structure called ionic lattice where the ions are arranged in an infinite alternating positive and negative pattern.

5.1.6 The properties of elements and compounds are determined by their bonding and structure * Explain why the formula for an ionic compound is an empirical formula * In ionic compounds, there are no infinite 3D arrays of positive and negative ions. * Thus, the chemical formula specifies a simple whole number ratio in which the ions are present, known as the empirical formula..
5.1.7 The properties of elements and compounds are determined by their bonding and structure * Identify common elements that exist as molecules or as covalent lattices * Magnesium – metallic * Barium chloride – ionic * Silicon dioxide – covalent network * Iodine – covalent molecular * Tetrabromomethane – covalent molecular * Phosphorous trioxide – covalent molecular * Lithium sulphide – Ionic * Diamond – covalent network
5.1.8 The properties of elements and compounds are determined by their bonding and structure * Explain the relationship between the properties of conductivity and hardness and the structure of ionic, covalent molecular and covalent network structures * They all have low conductivity * Ions in ionic compounds are strongly bonded by strong electrostatic forces of attraction, thus no freely moving electrons to produce electricity. * Covalent molecular substance have balanced or neutral charges, therefore they cannot produce electricity. * Covalent network lattices do not have any freely moving electrons in their structure, thus it has low electrical conductivity.
Covalent molecular Covalent network 5.2.3 The properties of elements and compounds are determined by their bonding and structure * 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
3.2.1 Element in Earth materials are present mostly as compounds because of interactions at the atomic level * Analyse information by constructing or using models showing the structure of metals, ionic compounds and covalent compounds
5.2.1 The properties of elements and compounds are determined by their bonding and structure * 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 (e.g. magnesium and oxygen)
5.2.2 The properties of elements and compounds are determined by their bonding and structure * 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 * Benefits of a scientific model * ‘A model is a representation of an abstract or conceptual scientific principle or reality’ * Advantages: * Provide a visual representation of the object or throughout makes it easier to understand and comprehend. * Can be used to predict any additional possibilities * Can be used to highlight similarities or differences between different phenomenon. * Limitations of a scientific model * Models are only approximations of natural phenomena and are inherently inexact. * Disadvantages: * They are only theories based on assumptions which may be false. * Can change overtime as new discoveries are made. * Are simplifications for the principle of conveying a main concept. * May not be able to accurately predict the future behaviour of the phenomenon correctly.
4.1.1 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 * Physical changes are changes where no new substances are formed.
E.g. boiling of water, bending of metal * Chemical changes are changes where that involve the breaking of chemical bonds and formation of new chemical bonds to form new substances.
E.g. electrolysis of water, metal dissolving in a solution of acid
4.1.2 Energy is required to extract elements from their naturally occurring sources * Summarise the differences between the boiling and electrolysis of water as an example of the difference between physical and chemical change | Boiling H2O(l)→H2O(g) | Electrolysis 2H2O(l)→O2(g)+2H2(g) | Physical VS Chemical change | Physical change where no new substances are formed | Chemical change where new substances are formed | Energy | Only requires a small amount of energy (2.3kJ) | Requires a large input of energy (30kJ) | Reversible | Easy to reverse as it involves a change in state | Difficult to reverse as it involves the breaking and formation a chemical bonds |

4.1.3 Energy is required to extract elements from their naturally occurring sources * 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
4.1.4 Energy is required to extract elements from their naturally occurring sources * 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 * Bonds in a compound are broken when they are heated, forming new separate atoms. * Heat is a form of energy. The more energy required to break the bond, means that the atoms in the compound are held strongly together, thus a strong force of attraction. * Hence: * More energy indicates a strong force of attraction
e.g. covalent network substances (strong, rigid lattice and also strong intramolecular bonds), ionic compounds (strong fore of attraction) and metals (positive lattice) * Less energy indicates a weak force of attraction
e.g. covalent molecular substances (weak intermolecular bonds)
4.2.1 Energy is required to extract elements from their naturally occurring sources * 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
4.2.2 Energy is required to extract elements from their naturally occurring sources * 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 and identify an application of the use of this reaction
4.2.3 Energy is required to extract elements from their naturally occurring sources * Analyse and present information to model the boiling of water and the electrolysis of water tracing the movements of and change sin arrangements of molecules
1.2.1 The living and non-living components of the Earth contain mixtures * Gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the Preliminary course