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Chemistry Textbook Notes
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Module 1- The Chemical Earth
Week 1/2:
Homogeneous substances are substances of uniform composition e.g. Pure water
Heterogeneous substances are substances of variable composition e.g. Tap water
Impure substance is a substance contaminated with other substances (mixture)
A compound is a pure substance that can be decomposed into smaller substances
They are broken down into elements (which cannot be decomposed)
Lithosphere (crust+ top part of mantle)- contains rocks, sand, soils, minerals
Hydrosphere (water of the Earth's crust)- contains water, sea water
Atmosphere (layer of gas above the Earth)- contains gases, nitrogen, oxygen, argon
Biosphere (inhabited portion of Earth)-contains living matter, organisms, plants
Sieving can separate solids of different sizes
Filtration, sedimentation, decanting can separate solids and liquids
Evaporation can separate dissolved solids in liquids
Distillation can separate two liquids if they have a different boiling points. Fractional
distillation is utilised when boiling points are <40 degrees in difference.
Separating funnels can be used to separate liquids of different densities
A solvent can be added to a mixture where one substance is soluble
Gases can be separated by using different boiling points or solubilities
Week 3:
Common properties of purse substances are colour, physical state, melting/boiling points,
density electrical conductivity, solubility in different liquids and mechanical properties.
Distinct colours e.g. Deep brown- liquid bromine, solid copper- reddish brown etc.
States of matter are solid, liquid or gas
Changes from solid to liquid to gas and vice versa are called changes of state
The melting point of a solid is the lowest temperature at which the solid changes to a
liquid
Melting points are sharp unless it is a mixture.
Opposite of melting point is freezing point which is exactly the same
Lowest temperature at which bubbles of vapour form is called the boiling point.
Boiling points are quite sharp can test purity of a substance
Converting a gas to a liquid is condensation or liquefaction
Density is defined as mass per unit volume e.g. Kg/meter cubed
Gravimetric analysis is determining the masses of substances in a sample
Free elements include oxygen and nitrogen, including noble gases
Most elements form as compounds because they are reactive
The more reactive an element is, less chance of finding it as an element
Metals are elements which are solid, shiny, good conductors and malleable/ductile
Semi-metals display characteristics of both metals and non-metals.
Elements are used due to their physical properties e.g. Aluminium- light but strong,
copper-high electrical conductivity, liquid nitrogen- low freezing and boiling points.
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Chemistry Textbook Notes
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Vertical columns of a Periodic Table are called groups (Valence electrons)
Horizontal rows of a Periodic Table are called periods (number of shells)
Two elements are liquids (mercury/ bromine), 11 are gases (noble gases + fluorine+
chlorine) while the rest of them are solids at room temperature.
Week 4:
Matter is made up of small particles
In solids, particles are packed tightly, liquids, less tightly and in gases, they are free
When heated, energy is transferred to the particles, causing them to vibrate
Atom is the smallest particle of an element
A molecule is the smallest particle of a substance that can exist alone.
Symbols are used to represent elements- lowercase for elements and uppercase for
compounds
Combination of symbols is called formulae.
A pair of atoms bonded in a molecule is called diatomic (O2) and one atom is called
monatomic, usually the noble gases.
In an atom, there exists a small dense nucleus and several electrons rapidly moving
around
Electrons move randomly in a volume described as the electron cloud
Atomic number of an element is the number of protons, mass number is protons +
neutrons
Each energy level can hold a certain amount of electrons, where 1st= 2, 2nd= 8, 3rd= 8 or
18 etc.
Most elements like to obtain its nearest noble gas electron configuration- losing or gaining
electrons to become an ion.
Electrons in the highest energy level (valence shell) are called valence electrons.
Formulae that give the ration of atoms by elements are called empirical formulae
Positive ions are called cations. Negative ions are anions
Elements in the same group tend to either gain or lose the same amount of electrons,
giving it similar properties (except for Group 4)
A covalent molecule is when an element shares electrons to obtain noble gas
configuration
Substances made from covalent molecules are called covalent molecular substances
Lewis dot structure is used to show electron configuration visually (see right)
Forces between pairs of molecules are called intermolecular forces (usually weak)
Covalent network solids are solids where covalent bonding occurs (covalent lattices)
Delocalised electrons hold positive ions in a lattice- making it malleable and ductile yet
hard.
Week 5:
Physical change- no new substance is formed
A change in which at least one new substance is formed is called a chemical change
Also called chemical reactions
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Chemistry Textbook Notes
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Usually defined by a gas being produced, a precipitate, change in colour, temperature
change, disappearance of a solid or an odour is produced.
In a chemical reaction, starting substances are reactants and products are formed
Mass and the number of atoms are conserved (Law of conservation of matter)
Physical properties e.g. melting and boiling points, chemical properties e.g. reactivity,
effect of light and decomposition of heat
Substances can be decomposed by heating them e.g. copper nitrate or through electricity
e.g. electrolysis of water, or through light e.g. silver salts
In physical change- particles are not changed, only in a chemical reaction
Direct combination reactions is when the elements react to form a compound e.g.
magnesium oxide.
The stronger a chemical bond is, the more energy is required to break the bonds.
Word equations are used to represent a reaction with symbolic equations- they must be
balanced.
Week 6:
The number of positive charges are equal to the negative charges in ionic compounds.
The valency is the numerical value of the charge that the ion of the element carries.
Binary compounds consist of two elements only. Ionic binary compounds consist of two
ionic substances. Named with positive ion than negative ion.
Compounds with three or more atoms are called polyatomic ions such as sulfur.
The valency of a covalent compound is the number of covalent bonds the element can
form.
Module 2: Metals/ The Mole
Week 1:
Alloys are homogeneous mixtures of a metal with one or more other elements.
Common examples are brass (copper+ zinc), bronze (copper+ tin), solder (tin+ lead),
stainless steel (iron+ chromium or nickel), steel (iron+ carbon)
Mild steel contains less than 0.2% carbon and is soft, structural steel contains up to 0.6%
carbon and is hard, while high-carbon steel contains up to 1.5% carbon and is very hard.
Electrical conductivity is the current passing through a metre cube when a voltage of 1
volt is applied across the opposite faces (megohm-1m-1)
Thermal conductivity is the energy transmitted per second through a metre cube of the
substance when there is a 1 degree temperature difference (Js-1m-1K-1)
Hardness can be measured through Mohs scale: from 1-10
Tensile strength is a measure of how well a material resists bending, twisting or
stretching.
Iron (usually in mild steel or structural steel) can be used for buildings, as it is cheap and
malleable, however it corrodes so it needs to be painted or galvanised with zinc.
Aluminium alloyed with copper, magnesium or manganese is light and strong, and does
not corrode. It is used for aeroplanes, windows, door frames, household utensils and
drink cans.
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Chemistry Textbook Notes
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First metal to be extracted was copper (copper oxide heated with charcoal) but it was
soft. Mined from 3000BCE, called the copper age.
When bronze was discovered (tin and copper ores) it became a favourite metal (hard, low
melting point and malleable) for ploughs and weapons (2000BCE)
Iron was extracted from iron oxide using a high temperature from 1200BCE which were
used for tools and weapons. This was known as the Iron Age.
Steel and iron increased during the Industrial Revolution with new alloys and metals in the
Modern Age e.g. cobalt, nickel, zinc, manganese, tungsten, titanium and chromium.
A mineral is a pure crystalline compound that occurs in the Earth's crust.
An ore is a compound or mixture of compounds from which it is economic or
commercially profitable to extract a desired substance such as a metal.
Week 2-3:
The reactivity of metals is ranked on an activity series, with oxygen or other substances.
Group 1 metals react rapidly with air, Group 2 react slowly but burn rapidly in air or
oxygen. Group 4 metals react slowly with air but only if heated forming ionic compounds.
Similarly the metals react with water in different ways as shown above.
A net ionic equation shows the actual ionic species that undergo change in the reaction.
A complete ionic equation shows all ions involved in the solution, including spectator ions
which do not undergo any change during a reaction.
Metals that react with oxygen, water and dilute acids lose electrons to form positive ions,
known as oxidisation reactions. The opposite is a reduction reaction known as electron
transfer reactions.
When there is a oxidisation and reduction reaction, it is called a redox reactions or a
electron-transfer reaction.
Half-reactions are reactions that describe the oxidation and reduction processes
separately in terms of electrons lost or gained.
An activity series is a list of metals in order of decreasing reactivity with oxygen, water or
dilute acids.
The first ionisation energy of an element is the energy required to remove an electron
from a gaseous atom of the element, usually measured in kilojoules per mole of atoms.
Reactivity of metals concerns the environment it is used in e.g. piping, body implants, roof
guttering- all of which use inert metals so they do not react with water etc.
Aluminium used to be an expensive metal due to its extraction process. Now Aluminium
can be converted to alumina (Al2O3) through the Bayer Process and melted with cryolite
and then electrolysed, the aluminium ions would be reduced to metal at the cathode.
However high cost of electrolysis and melting made it expensive. Now it is much cheaper
Alternative is to recycle aluminium, it uses less than 10% of the production energy costs.
Week 4-7:
Stoichiometry is the study of quantitative aspects of formulae and equationsstoichiometric equations are calculations based on this aspect.
Isotopes have a different mass of neutrons in the nucleus hence have different masses.
Atomic weight is the average mass of the element in the naturally occurring element
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Chemistry Textbook Notes
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Molecular weight of a compound is the sum of the atomic weights of the atoms
Formula weight is the sum of the atomic weights in a compound.
A mole of an element contains 6.022 x 10^23 atoms, same for a compound. Also known
as the Avagadro constant, number of atoms in 12 grams of carbon.
Molar mass is the mass of a mole, e.g. oxygen's molar mass is 16grams/mol. Be careful of
molecules and atoms, oxygen molecules is 32g/mol, oxygen atoms are 16g/mol
No. of moles = mass/ molar mass
No. of atoms = no. of moles x Avagadro constant.
Percentage compositions are used to determine the composition of an ore e.g. In Fe2O3,
70% is iron. % of iron = mass of iron in one mole/ mass of one mole of Fe2O3
Empirical formula tells us the ratio in which the atoms are present (simplified ratio). Can
be calculated by finding the moles of each substance, dividing by the smallest amount and
then rounding them or making them whole numbers.
The molecular formula is the unsimplified empirical formula e.g. C6H12O6 is molecular,
while empirical would be CH2O. To calculate have molecular mass/ empirical mass x
Empirical formula.
Write a balanced chemical equation- then find how much moles are needed, using
stoichiometry.
Look for the limiting reagent- a substance that runs out before the other does. Calculated
from the stoichiometry.
The yield of a metal is the mass of metal that is obtained from an ore. In theoretical
calculations we assume 100% yield, but there are real life problems like precipitating all of
the mineral out, and we can't achieve 100% efficiency. Using the yield percentage at the
end of the solution from your theoretical yield to your actual yield.
Gay-Lussac and Avagadro combined- one volume reacts with one volume to form two
volumes, works between hydrogen and chloride, two volumes reacts with one volume to
form two volumes e.g. 200ml hydrogen + 100ml oxygen = 200ml water
Week 8:
Dobereiner developed triads of elements that had similar properties
Newlands proposed a law of octaves of increasing atomic weight.
Mendeleev was the forerunner of the modern Periodic Table as was Meyer who arrange
in order of increasing atomic weight, those that had similar properties were called the
periodic law. Mendeleev was very successful, recognising gaps were elements were not
yet discovered.
However with atomic weight there were discrepancies, Moseley rearranged them by
atomic number and proposed the modified periodic law, properties of elements vary
periodically with their atomic numbers.
Atomic radius decreases across a period (as more protons slightly shrink the radius) while
it increases going down a group (another shell is added).
Melting and boiling points peak at Group 4 while they are at their lowest at noble gases
Ionisation energy is the minimum energy required to remove an electron from an atom of
an element in a gaseous state. Peaks at noble gases, reaches lowest at Group 1. The
more electrons lost, the more energy required until it finishes the shell and starts on the
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Chemistry Textbook Notes
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one underneath, in this case the energy jumps significantly. This trend can identify how
many valence electrons an element has. Ionisation energy decreases going down a period
since it is more reactive, loses electrons more readily.
Valency goes from 1-4. Anything with more than 4 valence electrons is subtracted form 8
Metal to non metal across a period, more metallic going down a group.
Reactivity decreases across a period, more reactive going down a group
Electronegativity is the ability to attract an electron when it forms compounds. It is
greatest near Group 7 and decreases going down a group.
Module 3: Water
Week 1:
Water is a raw material, a necessity for all living things, a solvent, a transport medium and
a thermal regulator.
Surface tension is the resistance of a liquid to increase its surface area. Higher surface
tension means it beads in a spherical drop rather than spread out.
Viscosity is the resistance of a liquid to flow through a tube, higher the viscosity, the less it
flows e.g. honey
Specific heat capacity of water is 4.18 J/K/g, it is how much energy required to heat one
gram of a substance by one kelvin.
Water has a bent structure/ shape of around 100 degrees.= as does hydrogen sulfide.
Ammonia has a pyramidal shape and methane has a tetrahedral structure.
Heteroatomic molecules like water have electron pairs distributed unevenly, forming
polar covalent bonds. These creates areas of charge called dipoles and thus these polar
molecules have a net dipole.
Electronegativities of atoms determine whether they are polar bonds and the shape
determines whether it has a net dipole.
Dipole-dipole forces are intermolecular forces present in polar covalent molecules like
hydrogen sulfide while dispersion forces are apparent in non-polar molecules like
methane.
The strongest of these bonds, the hydrogen bond occurs between hydrogen, oxygen,
nitrogen or fluorine atom. This means water which has hydrogen bonds has the highest
boiling point.
Surface tension occurs when the surface molecules have unbalanced forces since there
are no attractions above it, causing a inward force. Water is strong (H- bonds) and hence
has a high surface tension.
Viscosity depends on how long the molecule chains are, the longer the higher, and the
strength of the intermolecular bonds, more stronger, the more viscous.
The tetrahedral structure of atoms in ice leaves space in between which is why it expands
on freezing.
Week 2:
The solvent dissolves the solute to make a solution, occurs when a component is in larger
amount than the other.
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Chemistry Textbook Notes
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Ionic compounds are soluble in water, they break up into ions. Polar water molecules are
strongly attracted to the charged ions. Hence the ions become hydrated, and water is a
polar solvent, because it consists of polar molecules.
Water of crystallisation is when water becomes bound to a pure substances, known as
hydrates
Most molecular substances are non-polar and do not form hydrogen bonds with water,
and are hence insoluble or have poor solubility. Sugars can form hydrogen bonds hence it
dissolves. However non-polar substances dissolve in non-polar substances such as iodine.
Covalent lattices or large molecules do not dissolve since they are so big and have many
strong covalent bonds.
Week 3:
A solid is produced (precipitate) by two soluble solutions. This is called a precipitation
reaction.
Net ionic equation does not show spectator ions, complete ionic equation shows all ions
while neutral species equation shows normal balanced chemical equation.
A saturated solution is when a given amount of solvent in a temperature cannot dissolve
any more solute, e.g. too much salt in water- can't dissolve.
Concentration is the amount of solute present in a solvent or solution.
Different measures of concentration include mass/100ml (w/v), volume/100ml, (v/v),
%(w/v and % (v/v) are percentages of before. Also %(w/w) and ppm, grams of solute per
million grams of solution.
Measuring cylinders, pipettes, burette or volumetric flasks can be used
Dilution can change the concentration of a substance c1v1= c2v2
Molarity is no. of moles/ vol. of solution
Specific heat capacity can be measured by q= mc change in temperature.
Exothermic reactions release energy and endothermic reactions absorb energy.
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Chemistry Textbook Notes