Download GRADE 12A: Chemistry 1

GRADE 12A: Chemistry 1
UNIT 12AC.1
17 hours
The periodic table
About this unit
Previous learning
This unit is the first of eight units on chemistry for
Grade 12 advanced.
To meet the expectations of this unit, students should already be able to
recognise periodicity in the properties of elements and their compounds,
with particular reference to elements of groups I, II, VII and VIII and the first
transition series. They should know a variety of processes by which useful
substances are made from raw materials, including useful metals. They
should know the properties of the common compounds of silicon and the
characteristic properties of the first-row transition elements. They should
know that transition metals are important redox reagents because they
exhibit multiple oxidation states.
The unit is designed to guide your planning and
teaching of chemistry lessons. It provides a link
between the standards for science and your
lesson plans.
The teaching and learning activities should help
you to plan the content and pace of lessons.
Adapt the ideas to meet your students’ needs.
For consolidation activities, look at the scheme of
work for Grade 11A.
You can also supplement the activities with
appropriate tasks and exercises from your
school’s textbooks and other resources.
Introduce the unit to students by summarising
what they will learn and how this builds on earlier
work. Review the unit at the end, drawing out the
main learning points, links to other work and real
world applications.
Expectations
By the end of the unit, students recognise the periodic variation in
ionisation energies, electron affinity and electronegativity, and predict
properties of elements from their position in the periodic table. They know
the trends in the general properties of the s-, p- and d-block elements and
the specific properties and structures of some of their compounds.
Students who progress further recognise and understand the periodic
variation in ionisation energies, electron affinity and electronegativity, and
predict a vide variety properties of elements from their position in the
periodic table. They know and understand the trends in the general
properties of the s-, p- and d-block elements and many specific properties
and structures of a wide range of their compounds.
Resources
The main resources needed for this unit are:
•
•
•
•
data and hint cards (for details see notes section in the activities)
cards listing element symbols and electronegativity values
group I and II elements, pneumatic trough, pH paper
video clips of caesium and rubidium reacting with water
• group I and II nitrates, carbonates and hydroxides
• class sets of equipment to heat solids and collect the gas evolved by
bubbling through limewater
• aqueous solutions of halogens, aqueous solutions of potassium (or
sodium) halides, cyclohexane
• HCl, HBr, HI, gas jars
• solutions of potassium chloride, potassium bromide, potassium iodide, silver
nitrate solution, aqueous ammonia solution, halide solutions labelled A–E
• aqueous aluminium sulfate, dilute hydrochloric acid, dilute sodium hydroxide
• Internet access
• strips of aluminium, copper(II) chloride , mercury(II) chloride
• class sets of equipment to carry out electrolysis, aluminium strips, sulfuric
acid, alizarin red (or other suitable dye)
• spreadsheet package
• molecular models of diamond and silicon
• tin, lead, nitric acid, hydrochloric acid (dilute and concentrated),
concentrated sodium hydroxide solution, potassium iodide
• ammonium vanadate(V), zinc granules, acidified potassium manganate(VII),
iron(II) ammonium sulfate, potassium iodide, sodium thiosulfate, sodium sulfite
• mode-building kit
• nickel(II) chloride, concentrated hydrochloric acid, sodium hydroxide
solution, Na2H2edta
Key vocabulary and technical terms
Students should understand, use and spell correctly:
•
•
•
•
•
455 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
ionisation energy, electron affinity, electronegativity
thermal stability
amphiprotic, anodise
orbitals, redox, oxidising agents, reducing agents
ligand, complex, ligand exchange, coordinate bond, coordination number
© Education Institute 2005
Standards for the unit
17 hours
SUPPORTING STANDARDS
Unit 12AC.1
CORE STANDARDS
Grade 12 standards
EXTENSION STANDARDS
12A.19.1 Understand and use the term ionisation energy. Explain the factors
3 hours
influencing the ionisation energies of elements and the trends in
ionisation energies across a period and down a group of the periodic
table.
Periodicity in
properties
12A.19.2 Understand the terms electron affinity and electronegativity and recognise
4 hours
s-block elements
6 hours
p-block elements
and explain their periodic variation.
10A.19.4 Describe trends in the physical and
chemical properties of the elements,
and their simple compounds, within
groups I, II, VII and VIII, and account
for these trends in terms of electronic
structure.
4 hours
12A.19.3 Know the general chemistry of the s-block elements, including:
• trends in the physical properties of the elements;
• trends in the chemical properties of the elements;
• general common properties of the compounds of the elements,
including the solubility, colour and thermal stability of the nitrates,
carbonates and hydroxides;
• the occurrence and extraction of the elements.
d-block elements
12A.19.4 Outline and explain qualitatively the trends in the thermal stability of group II
nitrates and carbonates and the variation in solubility of group II sulfates.
12A.19.5 Outline and explain trends in a number of properties down group VII:
• physical properties;
• the reactivity of the elements as oxidising agents;
• the thermal stability of the hydride;
• the reaction of the halide ions with silver nitrate followed by aqueous
ammonia.
10.18.5 Explain, including the electrode
12A.19.6 Know how aluminium occurs and how it is extracted. Describe the main
reactions, industrial electrolytic
processes such as: …
properties of aluminium, including:
• the extraction of aluminium from
molten aluminium oxide in
cryolite; …
• the suppression of the natural reactivity of the metal;
• the amphiprotic nature of the ion in its salts and solution;
• anodising.
12A.19.7 Explain how the small size and high charge of the aluminium ion leads to
partial covalent bonding and its amphiprotic properties.
11.21.15 Compare and contrast the physical
and (inorganic) chemical properties
of the group IV elements carbon and
silicon and their properties
12A.19.8 Outline and explain, in terms of structure and bonding, trends in a number
of properties down group IV:
• melting point and electrical conductivity of the elements;
• the increased stability of the lower oxidation state;
• the bonding, acid–base nature and thermal stability of the oxides;
• the bonding in the chlorides, their volatility and their reaction with water.
456 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005
17 hours
SUPPORTING STANDARDS
11.22.2 Know the electronic configurations
and the typical properties of the
first-row transition elements
CORE STANDARDS
Grade 12 standards
EXTENSION STANDARDS
12A.19.9 Know that in transition metals, d-electrons can be involved in bonding as
well as the outer s-electrons, resulting in multiple oxidation states. Predict
from its electronic configuration, the likely oxidation states of a transition
element.
11.22.4 Know that transition metals can
form one or more stable ions
through the involvement of electrons
from the inner (d) orbitals and know
that this results in multiple oxidation
states.
.
12A.19.10 Explain how the variable oxidation states can result in transition metal ions
acting as oxidising and reducing agents. Give examples of transition metal
redox systems.
12A.19.11 Know that transition elements combine with ligands through dative bonding
to form complexes and that these are often coloured. Give examples of
ligand exchange reactions.
12A.19.12 Know that ligands in transition metal complexes may be neutral or anionic,
and that the complexes usually exhibit four-fold (planar or tetrahedral) or
six-fold (octahedral) coordination.
12A.19.13 Explain the formation of complexes in terms of coordinate bonds and the
splitting of d-electron energy levels and know how this explains the colour of
many transition metals’ complex ions.
11.22.3 State some common uses of some
12A.19.14 Know the biochemical importance of cobalt and iron.
transition elements, including
examples of catalysis by transition
metals, and relate these uses to their
properties
457 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005
Activities
Unit 12AC.1
Objectives
Possible teaching activities
3 hours
Introduce the definition of ionisation energy to students and ask them to work individually to
produce an equation of the type
Periodicity in properties
Understand and use the term
ionisation energy. Explain the
factors influencing the
ionisation energies of
elements and the trends in
ionisation energies across a
period and down a group of
the periodic table.
Understand the terms
electron affinity and
electronegativity and
recognise and explain their
periodic variation.
4 hours
s-block elements
Know the general chemistry
of the s-block elements,
including:
• trends in the physical
properties of the elements;
• trends in the chemical
properties of the elements;
• general common
properties of the
compounds of the
elements, including the
solubility, colour and
thermal stability of the
nitrates, carbonates and
hydroxides;
• the occurrence and
extraction of the elements.
Notes
M (g) → M+ + e–
Then give small groups of students data for the ionisation energies of a given period, group 1or
group 7. Ask each group to prepare a short presentation explaining the data they have been
given. Each group then pairs up with another group with a different set of data and peer teach
their interpretations. This process is repeated with a third group so all the data has been
covered.
Prepare sets of suitable data.
Introduce the definition of electron affinity and electronegativity to students. Ask them, in small
groups, to list factors that will affect the electronegativity of an element. Give each group a set of
cards in two halves. One half has the symbols of elements and the other set has
electronegativity values. Tell them to match the element to its electronegativity, giving reasons
in each case.
Prepare cards listing element symbols and
electronegativity values.
School resources
Use this column to note
your own school’s
resources, e.g.
textbooks, worksheets.
Provide each group with a periodic table and ask them to predict the trends in electronegativity
across a period. Ask them then to predict the periodic variation in electronegativities. Provide
them with the appropriate data to check to see if their predictions are correct.
Allow students to view samples of lithium, sodium and potassium so that they can compare the
elements’ physical appearances at room temperature. Then ask them to research the Internet
for data on other physical properties (e.g. melting points, boiling points, atomic radius, electron
structure, principal oxidation number, electrical conductivity) in order to draw up a chart to
compare and contrast the properties.
Safety: Students should not handle sodium or
potassium.
ICT opportunity: Use of the Internet.
Get students to repeat the process for the group II elements magnesium and calcium.
Encourage students to use the data they have collected to draw comparisons between the two
groups and find common patterns in the properties across the two groups.
Demonstrate the reactions of sodium and potassium with cold water in a pneumatic trough and
check the pH of the resultant solution. Allow students to react lithium, calcium and magnesium
with cold water themselves and check the pH of the resultant solutions. Show video clips of the
reactions of more reactive s-block metals with water.
Ask students to place samples of magnesium oxide, calcium oxide and barium oxide in water
and check the pH of the resultant solutions.
Safety: Students should not handle sodium or
potassium. The reactions should be
demonstrated using a pneumatic trough.
Show video clips of caesium and rubidium
reacting with water.
Students will need pH paper.
Then ask them, in pairs, to produce a visual representation of any trends in reactivities.
Enquiry skill 12.3.4
Provide samples of group I and II nitrates, carbonates and hydroxides for visual inspection. Tell
students to record the visual features of these compounds.
Students will need appropriate equipment to
heat solids and collect the gas evolved by
bubbling through limewater.
[continued]
458 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005
Objectives
Possible teaching activities
[continued]
Ask students to heat samples of magnesium carbonate, calcium carbonate and barium
carbonate, passing any gas evolved through limewater to test for carbon dioxide. From their
observations they will be able to construct equations for the reactions and determine any trends
in the thermal stability of the metal carbonates.
Outline and explain
qualitatively the trends in the
thermal stability of group II
nitrates and carbonates and
the variation in solubility of
group II sulfates.
Notes
School resources
Enquiry skill 12.4.1
Ask students to design a simple experiment to determine the relative solubilities of group I and II
nitrates, carbonates and hydroxides then carry out their experiment. From this they can draw
out trends in solubilities.
Give students data for the solubility of the group II sulfates at a given temperature. Ask them to
work in small groups to try to interpret why the solubility decreases on going down the group.
You may like to produce ‘hint cards’ (e.g. one card might read ‘In order for a substance to
dissolve, what are the energy changes involved?’) On completion of the task, ask groups to
feed back their ideas to the whole group for class discussion.
Prepare hint cards.
Having established a trend of increasing thermal stability of the carbonates on going down
group II, ask students to work in small groups to discuss the findings and to explain why they
occur. You may like to produce a series of ‘hint cards’ to help students who are struggling
(e.g. one card might read ‘What is the charge density on a group II metal ion? What effect will
this have on a negative ion near it?’).
Prepare hint cards.
Enquiry skills 12.1.1–12.1.4
Once students have understood what is happening, ask them to predict (with reasons) what
they think is the relative stability of group II nitrates. On completion of the task, ask groups to
feed back their ideas to the whole group for class discussion.
6 hours
p-block elements
Outline and explain trends in
a number of properties down
group VII:
• physical properties;
• the reactivity of the
elements as oxidising
agents;
Give each student at random, the name of one of the group I or II elements. Then tell them to
team up with anyone else in the class who has the same element and together use the Internet
to research the occurrence and extraction of the element. Tell them to produce a summary
sheet of notes for the rest of the class.
ICT opportunity: Use of the Internet.
Allow students to view samples of chlorine, bromine and iodine so that they can compare the
elements’ physical appearances at room temperature. Then ask them to research the Internet
for data on other physical properties (e.g. melting points, boiling points, atomic radius, electron
structure, principal oxidation number, electrical conductivity) in order to draw up a chart to
compare and contrast the properties.
Safety: Chlorine must be kept in a sealed gas
jar and bromine in a sealed container. Both
should be kept in a fume cupboard and only
handled by a teacher.
Enquiry skill 12.3.4
ICT opportunity: Use of the Internet.
Show students the colours that form when aqueous solutions of chlorine, bromine and iodine
are added to cyclohexane.
Provide students with aqueous solutions of chlorine, bromine and iodine, and solutions of
potassium halides. Ask students to produce all the combinations of solutions of halogen
elements with solutions of halide salts and record their observations. In order to improve clarity,
• the thermal stability of the
students may wish to add a few drops of cyclohexane to each mixture and record any colour
hydride;
changes to the organic layer. Tell students to use their observations to deduce a balanced
• the reaction of the halide ions
formula equation for each reaction occurring. They can then work in small discussion groups to
with silver nitrate followed by
produce ion equations for each reaction. Explain why these are redox reactions and encourage
aqueous ammonia.
students to deduce an order for the relative oxidising power of the halogens.
[continued]
459 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
Enquiry skills 12.3.1, 12.3.3
© Education Institute 2005
Objectives
Possible teaching activities
[continued]
Demonstrate what happens on heating hydrogen halides: no decomposition of HCl on heating;
brown fumes on heating HBr; copious violet fumes on plunging a heated glass rod into a gas jar
of HI. Ask students to research the bond lengths and bond enthalpies of the hydrogen halides
and plot these against atomic number. Then tell them to interpret the data and relate it to the
observations of the practical demonstration.
Know how aluminium occurs
and how it is extracted.
Describe the main properties
of aluminium, including:
• the amphiprotic nature of
the ion in its salts and
solution;
• the suppression of the
natural reactivity of the
metal;
• anodising.
Explain how the small size
and high charge of the
aluminium ion leads to partial
covalent bonding and its
amphiprotic properties.
Outline and explain, in terms
of structure and bonding,
trends in a number of
properties down group IV:
• melting point and electrical
conductivity of the
elements;
• the increased stability of
the lower oxidation state;
• the bonding, acid–base
nature and thermal stability
of the oxides;
• the bonding in the
chlorides, their volatility
and their reaction with
water.
Notes
School resources
Safety: Carry out the demonstration in a fume
cupboard.
Allow students to add silver nitrate solution to aqueous solutions of potassium chloride,
potassium bromide and potassium iodide, and tell them to record the colours of the precipitates
formed. Then tell them to add aqueous ammonia solution to each precipitate and record their
observations. Students should be able to produce balanced equations for each reaction and
write a method to test for the presence of chloride, bromide and iodide, respectively. Give the
class unknown samples of halide solutions labelled A–E and ask them to use the tests they
have just developed to determine which halide ion (if any) is present in each solution.
Use a revision quiz to remind students about the occurrence and extraction of aluminium from
molten aluminium oxide in cryolite.
Prepare a suitable revision quiz.
Encourage students to find out the meaning of amphiprotic. Ask them, individually, to measure
the pH of an aqueous solution of aluminium sulfate. Then tell them to add alkali a drop at a time
until a precipitate forms and then redissolves. They can then reverse the process by adding
dilute acid a drop at a time. Provide students with a series of cards, each of which has a
reactant, a product or arrows drawn on it. Tell students, in pairs, to arrange the cards to
represent the reactions that have occurred. Once they have done this, they will be able to
identify how the aluminium salt in solution has behaved in an amphiprotic way. A class
discussion can lead to an understanding of how the high charge density on the small aluminium
ion leads to these reactions occurring.
Students will need an aqueous solution of
aluminium sulfate, dilute sodium hydroxide and
dilute hydrochloric acid.
Allow students to research the Internet for the uses for aluminium. Provide them with the
standard electrode potentials for aluminium and iron in order to pose the dilemma that
aluminium reacts easily, yet for the uses it is put, to aluminium needs to have minimal corrosion.
Ask students to observe and record what happens to strips of aluminium when they are:
(a) immersed in dilute sodium hydroxide solution; (b) immersed in dilute hydrochloric acid;
(c) left exposed to the air. Then tell students to treat aluminium strips with copper(II) chloride
solution and repeat the practical above. If you wish, you could, as a demonstration, treat
aluminium strips with mercury(II) chloride and repeat the practical. Both these treatments will
allow students to see the difference in reactivity of clean aluminium compared with oxidised
aluminium.
ICT opportunity: Use of the Internet.
Ask small groups of students to anodise aluminium (in the fume cupboard). The electrolyte used
can be 1 mol dm–3 sulfuric acid. After electrolysis, tell students to test the conductivity of the
anode and cathode. They could also try dyeing the anode and cathode with a solution of alizarin
red, or some other suitable dye. Encourage them to discuss the advantages and applications of
anodised aluminium.
Students will need equipment to carry out
electrolysis, aluminium strips, sulfuric acid and
alizarin red (or other suitable dye).
460 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
Enquiry skill 12.4.1
Safety: Mercury(II) chloride is highly toxic by
ingestion and skin absorption, so it must only be
used by a teacher.
Enquiry skill 12.4.1
© Education Institute 2005
Objectives
Possible teaching activities
Notes
Ask students to investigate the trend from non-metallic to metallic on going down group IV of
the periodic table. Ask them to research and plot graphs of the melting points, boiling points and
electrical conductivity of the group IV elements. Let them download images of the structures of
these elements and give them models of the giant structures of diamond and silicon to examine.
Then ask them to work in small groups to explain how the properties they have researched are
accounted for in terms of structure and bonding, and to present their ideas orally to the rest of
the class.
ICT opportunity: Use of the Internet and
suitable spreadsheet software to enter data in
order to plot graphs of melting points, boiling
points and electrical conductivity.
Give students a list of typical compounds of the group IV elements. This allows them to see the
relative increase in frequency of the +2 oxidation state (as opposed to +4) on going down the
group. Provide students with data relating to 1st, 2nd, 3rd and 4th ionisation energies for the
group IV elements. Divide the class in half. Ask one half to draw a bar chart of 1st + 2nd IE
values for each element and the other half to draw a bar chart of the 1st + 2nd + 3rd + 4th IE
values for each element. This can lead to a whole class discussion on how the relative increase
in the total energy needed to form Pb+4 compared with Sn+4 is so much greater than the relative
increase in the total energy needed to form Pb+2 compared with Sn+2
Students will need data relating to ionisation
energies and bond enthalpy data.
School resources
To help students understand why carbon normally forms four covalent bonds, give them bond
enthalpy data for Pb–Cl and C–Cl bonds and ask them to decide, on their own, what needs to
happen to outer electrons in order for four bonds to be formed. Ask them to use the data you
have provided to explain why it is energetically favourable for this to occur in carbon compounds
but much less likely in lead compounds.
Provide students with data referring to the melting points, boiling points and solubility in water
for carbon dioxide, silicon(IV) oxide and lead(II) oxide. Then let them download 3D animations
(Java applets) of the structures of these compounds and use these to explain the differences in
properties. Encourage them to research the reactions of group IV oxides with acids and bases
in order to establish that they become more basic in character on going down the group.
Ask students to prepare tin(IV) oxide and lead(IV) oxide by the action of concentrated nitric acid
on each metal. Then tell them to heat the oxides they have synthesised and observe their
reactions with dilute hydrochloric acid, concentrated hydrochloric acid, concentrated sodium
hydroxide and acidified potassium iodide. Ask them to write equations for what is occurring.
Ask students to research the thermal stability of the oxides and interpret any trends in terms of
structure.
ICT opportunity: Use of the Internet and Java
applets.
Safety: Concentrated acids and alkalis are
corrosive. The vapours are harmful to lungs,
eyes and skin. Concentrated nitric acid is an
oxidising agent. Students must wear eye
protection, gloves and protective clothing, and
carry out the activities in a fume cupboard.
Students will need: tin, lead, nitric acid,
hydrochloric acid (dilute and concentrated),
concentrated sodium hydroxide solution,
potassium iodide.
Enquiry skills 12.4.1, 12.4.2
All group IV elements form chlorides of the formula type XCl4. Encourage students to build
models of these compounds in order to explain their low boiling points. Tell them to look up the
reactions of the chlorides with water and work in small discussion groups to explain why CCl4
does not react with water, yet SiCl4 is readily hydrolysed. They also need to consider why PbCl2
does not react with water. Ask them to make a poster display of their findings.
461 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
Students will need model-building kits.
ICT opportunity: Use of the Internet.
Enquiry skill 12.3.4
© Education Institute 2005
Objectives
Possible teaching activities
4 hours
Revisit the work done in Grade 11 relating to the fact that transition metals can form one or
more stable ions through the involvement of electrons from the inner (d) orbitals and that this
results in multiple oxidation states. Ask students to write out the electronic configurations for
each of the first row transition metals. Taking into account the s3d and 4s electrons, ask them to
predict which ions they think would occur most readily and to check the literature to support this.
d-block elements
Know that in transition
metals, d-electrons can be
involved in bonding as well as
the outer s-electrons,
resulting in multiple oxidation
states. Predict from its
electronic configuration, the
likely oxidation states of a
transition element.
Explain how the variable
oxidation states can result in
transition metal ions acting as
oxidising and reducing
agents. Give examples of
transition metal redox
systems.
Know that transition elements
combine with ligands through
dative bonding to form
complexes and that these are
often coloured. Give
examples of ligand exchange
reactions.
Know that ligands in
transition metal complexes
may be neutral or anionic,
and that the complexes
usually exhibit four-fold
(planar or tetrahedral) or sixfold (octahedral) coordination.
Provide students with standard electrode potential values for the reactions to follow. Ask them
to reduce a solution of ammonium vanadate(V) to vanadium(II) using zinc granules, then
oxidise the vanadium(II) to vanadium(V) using acidified potassium manganate(VII), then work
out, using the electrode potential values. what reactions have occurred..
Notes
School resources
Students will need: data relating to standard
electrode potentials, ammonium vanadate(V),
zinc granules, acidified potassium
manganate(VII), iron(II) ammonium sulfate,
potassium iodide, sodium thiosulfate, sodium
sulfite.
Enquiry skill 12.3.4
Depending on time available and abilities of students, ask students to predict what they will
observe when:
• VO2+ reacts with Fe2+, VO2+ reacts with I- (followed by the addition of thiosulfate);
• VO2+ reacts with SO2 then has vanadium(II) added.
Then let them carry out these reactions, compare them with their predictions and complete half
equations for the reactions occurring.
Give students a series of diagrams and models of transition metal complexes. Ask them to
make a list of the features that constitute a complex. You may wish to guide them in their
observations (e.g. ‘What do they all have in common?’, ‘What overall charge does the complex
carry?’, ‘What type of bonding is present?’, ‘What shape has the complex adopted?’).
Students will need diagrams and models of a
wide range of complexes.
Develop the terminology needed for this topic through class discussion of these ideas.
Give students solid nickel(II) chloride and get them to make up an aqueous solution, add a few
drops of concentrated hydrochloric acid, dilute with water, add sodium hydroxide solution and
then add Na2H2edta. Tell them to record any colour change and write balanced equations for
the reactions at each stage. Students might also investigate the formation of complexes
between a number of transition metal ions and the ligands ammonia and edta4–.
Students will need nickel(II) chloride,
concentrated hydrochloric acid, sodium
hydroxide solution, Na2H2edta.
Enquiry skills 12.4.1, 12.4.2
Their findings will help them develop an understanding of ligand exchange.
Divide the class into two and ask one half of students (working individually) to prepare a 5minute lesson to explain the formation of complexes in terms of coordinate bonds and the
splitting of d-electron energy levels. Ask the other half of the class (also working individually) to
prepare a 5-minute lesson to explain how this brings about the colour of many transition metals’
complex ions. Tell all students to prepare some consolidation exercises on the topic
(e.g. crosswords, card-matching activities). When they have completed this, ask students to pair
up with someone in the opposite half of the class. Then tell each student to present their lesson,
possibly using PowerPoint or other presentation software, and ask their ‘pupil’ to complete the
consolidation exercise. The roles are then reversed.
Explain the formation of
complexes in terms of
coordinate bonds and the
splitting of d-electron energy
levels and know how this
Ask students to prepare a poster presentation for the class on the biochemical importance of
explains the colour of many
cobalt and iron.
transition metals’ complex ions.
ICT opportunity: Use of PowerPoint or similar
package.
Enquiry skill 12.3.4.
ICT opportunity: Use of the Internet.
Enquiry skill 12.3.4
Know the biochemical
importance of cobalt and iron.
462 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005
Assessment
Examples of assessment tasks and questions
Assessment
The halogens form a well-defined group of elements.
Set up activities that allow
students to demonstrate what
they have learned in this unit.
The activities can be provided
informally or formally during
and at the end of the unit, or
for homework. They can be
selected from the teaching
activities or can be new
experiences. Choose tasks
and questions from the
examples to incorporate in
the activities.
Explain how the following support this statement:
Unit 12AC.1
Notes
School resources
a. electron structure;
b. redox behaviour;
c. physical properties of the elements;
d. thermal stability of the hydride.
Explain, giving examples why the elements in group IV become more metallic on going down
the group.
Complexes formed by edta4– involve pairs of electrons on nitrogen and oxygen atoms in the
same way as complexes formed by NH3 and H2O. Explain why stability constants of edta
complexes in aqueous solution are generally so much larger than those of corresponding
complexes with NH3 and H2O.
From G. Burton, 2000, Salters Advanced Chemistry, Chemical Ideas, 2nd edn,
Heinemann, p.273
Describe and account for the trends in thermal stabilities of the group II carbonates.
463 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005
464 | Qatar science scheme of work | Grade 12 advanced | Unit 12AC.1 | Chemistry 1
© Education Institute 2005