KEY:
Topic:
Definitions + Calculations + Theory Answers
QW: Question Word and How to do Question (e.g. Evaluate)
Graph Calculations + Explain Trend:
Method for Core Practicals:
Mistakes in Practical Methods + Improve Accuracy:
Exam Practice Additions
CHEMISTRY
1. States of Matter:
Solute – substance being dissolved
Solvent – liquid that solute dissolves into
Solution – mixture of solute and solvent
Saturated solution – a solution where no more solute can dissolve in the solvent.
Solubility – the maximum mass of solute that can dissolve in 100g of a solvent at a given
temperature. Solubility of most substances increases as temperature increases.
Solubility per 100g = (mass obtained/ mass of water) * 100
Diffusion – net movement of particles from an area of high to low concentration
Potassium permanganate + Water: Crystal slowly dissolves in water, purple colour
diffuses evenly throughout liquid (dilution).
Ammonia + hydrogen chloride: Ring forms closer to HCl, ammonia molecules have a
lower mass so move faster.
Takes time for ammonium chloride ring to form: Collide with air particles in tube +
collide with walls of tube.
Bromine gas + air: Half gas and half air, when plate is removed, diffusion occurs, paler
colour.
Graph:
Substance cooled from temperature to different temperature:
Ans = old temp Ans – new temp Ans
If cm3 of graph is less than 100:
Solubility = (100/ cm3 of water on graph) * graph value
Method:
Saturated solution of ammonium chloride in distilled water in boiling tube.
Transfer to water bath at 25C and stir, check all excess solid has sunk to bottom.
Weigh evaporating basin, pour some solution in basin (not undissolved solid).
Weigh basin and contents.
Gently heat using Bunsen burner.
Once all water has evaporated, reweigh basin and contents.
Repeat at different temperatures (e.g. 35, 45, 55)
Mistakes:
Not stirred enough, not enough water, not right temperature.
Some ammonium chloride evaporated, heated too strongly.
,2. Elements, Compounds and Mixtures:
Element – pure substance made up of only one type of atom.
Compound – pure substance made up of multiple elements chemically bonded
together.
Mixture – group of substances, not chemically bonded together.
Pure substance – element/compound, fixed m.p and b.p.
Impure substance – mixture, melts/boils over a range of temperatures.
Simple distillation – used to separates liquids with very different
boiling points (one with dissolved solid):
1. Solution is heated and vapourised.
2. Vapour is cooled, condensed and collected
Fractional distillation – used to separate liquids with boiling points:
1. Liquids evaporate at different temperatures.
2. Liquid with lowest b.p evaporates first and reaches top of
fractionating column.
3. When first liquid is collected, raise temperature and
collect next liquid.
Chromatography:
QW: Deduce conclusions- How many colours in the ink? Which Dyes?
Rf Value = Distance moved by spot/ Distance moved by solvent
Rf Value cannot be greater than 1 as solvent will always move further.
If spot does not move, dye is insoluble in water. (Use different solvent).
The further the spot moves, the more soluble it is.
Method:
Pour solvent in beaker.
` Place paper (containing dots on baseline) in solvent so baseline is above
level of solvent.
Leave paper and let solvent rise until it reaches almost the top of the
paper.
Mistakes:
Solvent should be below baseline to prevent spots dissolving in solvent.
Baseline should be drawn in pencil because ink would interfere with
results by dissolving in the solvent.
Crystallisation Method:
1. Filter out … from solution (other product/ undissolved solute)
2. Heat the solution until crystals form on a glass rod
3. Leave the solution out to cool and crystallise
4. Filter off excess liquid to obtain the crystals
5. Dry the crystals using a filter paper
Crystals form when left to cool, as they are less soluble in cold water.
, 3. Atomic Structure:
Atom – smallest particle of an element that can take part in chemical change.
Molecule – atoms that are chemically bonded together.
Proton – Mass = 1, Charge = +1
Neutron – Mass = 1, Charge = 0
Electron – Mass =1/2000, Charge = -1
Atomic number – number of protons/electrons
Mass number – sum of protons and neutrons
Isotopes – atoms of the same element with the same number of protons but different
number of neutrons.
Ar = (mass * percent/100) + (mass*percent/100) …
Relative atomic mass is the average mass of one atom of an element compared to 1/12
of a 12C atom.
QW: Evaluate – What is correct? + What is incorrect?
4. Periodic Table:
Periodic table is arranged by atomic number in periods (rows).
Groups: Elements with similar properties, same number of electrons on outer shell.
Noble Gases are monatomic: They exist as single atoms, Contain full outer shell of
electrons, unreactive.
Group 1: Metals, Contain 1 electron on outer shell, Form positive ions, Lose 1 electron.
Group 7: Covalently bond, Form negative ions, Need 1 electron.
Compare? Details about X? Details about Y?
Why X rather than Y? Why not X? Why Y?
Topic:
Definitions + Calculations + Theory Answers
QW: Question Word and How to do Question (e.g. Evaluate)
Graph Calculations + Explain Trend:
Method for Core Practicals:
Mistakes in Practical Methods + Improve Accuracy:
Exam Practice Additions
CHEMISTRY
1. States of Matter:
Solute – substance being dissolved
Solvent – liquid that solute dissolves into
Solution – mixture of solute and solvent
Saturated solution – a solution where no more solute can dissolve in the solvent.
Solubility – the maximum mass of solute that can dissolve in 100g of a solvent at a given
temperature. Solubility of most substances increases as temperature increases.
Solubility per 100g = (mass obtained/ mass of water) * 100
Diffusion – net movement of particles from an area of high to low concentration
Potassium permanganate + Water: Crystal slowly dissolves in water, purple colour
diffuses evenly throughout liquid (dilution).
Ammonia + hydrogen chloride: Ring forms closer to HCl, ammonia molecules have a
lower mass so move faster.
Takes time for ammonium chloride ring to form: Collide with air particles in tube +
collide with walls of tube.
Bromine gas + air: Half gas and half air, when plate is removed, diffusion occurs, paler
colour.
Graph:
Substance cooled from temperature to different temperature:
Ans = old temp Ans – new temp Ans
If cm3 of graph is less than 100:
Solubility = (100/ cm3 of water on graph) * graph value
Method:
Saturated solution of ammonium chloride in distilled water in boiling tube.
Transfer to water bath at 25C and stir, check all excess solid has sunk to bottom.
Weigh evaporating basin, pour some solution in basin (not undissolved solid).
Weigh basin and contents.
Gently heat using Bunsen burner.
Once all water has evaporated, reweigh basin and contents.
Repeat at different temperatures (e.g. 35, 45, 55)
Mistakes:
Not stirred enough, not enough water, not right temperature.
Some ammonium chloride evaporated, heated too strongly.
,2. Elements, Compounds and Mixtures:
Element – pure substance made up of only one type of atom.
Compound – pure substance made up of multiple elements chemically bonded
together.
Mixture – group of substances, not chemically bonded together.
Pure substance – element/compound, fixed m.p and b.p.
Impure substance – mixture, melts/boils over a range of temperatures.
Simple distillation – used to separates liquids with very different
boiling points (one with dissolved solid):
1. Solution is heated and vapourised.
2. Vapour is cooled, condensed and collected
Fractional distillation – used to separate liquids with boiling points:
1. Liquids evaporate at different temperatures.
2. Liquid with lowest b.p evaporates first and reaches top of
fractionating column.
3. When first liquid is collected, raise temperature and
collect next liquid.
Chromatography:
QW: Deduce conclusions- How many colours in the ink? Which Dyes?
Rf Value = Distance moved by spot/ Distance moved by solvent
Rf Value cannot be greater than 1 as solvent will always move further.
If spot does not move, dye is insoluble in water. (Use different solvent).
The further the spot moves, the more soluble it is.
Method:
Pour solvent in beaker.
` Place paper (containing dots on baseline) in solvent so baseline is above
level of solvent.
Leave paper and let solvent rise until it reaches almost the top of the
paper.
Mistakes:
Solvent should be below baseline to prevent spots dissolving in solvent.
Baseline should be drawn in pencil because ink would interfere with
results by dissolving in the solvent.
Crystallisation Method:
1. Filter out … from solution (other product/ undissolved solute)
2. Heat the solution until crystals form on a glass rod
3. Leave the solution out to cool and crystallise
4. Filter off excess liquid to obtain the crystals
5. Dry the crystals using a filter paper
Crystals form when left to cool, as they are less soluble in cold water.
, 3. Atomic Structure:
Atom – smallest particle of an element that can take part in chemical change.
Molecule – atoms that are chemically bonded together.
Proton – Mass = 1, Charge = +1
Neutron – Mass = 1, Charge = 0
Electron – Mass =1/2000, Charge = -1
Atomic number – number of protons/electrons
Mass number – sum of protons and neutrons
Isotopes – atoms of the same element with the same number of protons but different
number of neutrons.
Ar = (mass * percent/100) + (mass*percent/100) …
Relative atomic mass is the average mass of one atom of an element compared to 1/12
of a 12C atom.
QW: Evaluate – What is correct? + What is incorrect?
4. Periodic Table:
Periodic table is arranged by atomic number in periods (rows).
Groups: Elements with similar properties, same number of electrons on outer shell.
Noble Gases are monatomic: They exist as single atoms, Contain full outer shell of
electrons, unreactive.
Group 1: Metals, Contain 1 electron on outer shell, Form positive ions, Lose 1 electron.
Group 7: Covalently bond, Form negative ions, Need 1 electron.
Compare? Details about X? Details about Y?
Why X rather than Y? Why not X? Why Y?
