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Course
Subject Topic
Pages
Additional science
Chemistry
Pages 108–109
C2 3.1 The mass of atoms
Learning
objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 what atomic number
and mass number
mean
 the relative masses
of subatomic
particles
 what isotopes are.
Most students should be able to:
 define atomic number and mass
number
 use the periodic table to get
atomic numbers and mass
numbers for any atom and work
out the number of each
subatomic particle that an atom
has state a definition of isotopes.
Some students should also be able
to:
 compare the physical and
chemical properties of isotopes
of an element.
Atoms can be represented as shown in this example:
Mass number
Chapter map:
How much?
Teacher notes:
How much?
Support: All
about atoms
Atomic number [C2.3.1 a)]
The relative masses of protons, neutrons and electrons … .
[C2.3.1 b)]
The total number of protons and neutrons in an atom is called
its mass number. [C2.3.1 c)]
Atoms of the same element can have different numbers of
neutrons; these atoms are called isotopes of that element.
[C2.3.1 d)
Lesson structure
Support, Extend and Practical
notes
Starters
True or false – If students agree with these statements they should show a thumbs-up sign. If they
disagree, their thumbs should point downwards, and if they don’t know their thumbs should be
horizontal.
 Atoms are charged particles. [False]
 Atoms contain charged particles. [True]
 Electrons are found in energy levels or shells. [True]
 Electrons have a negative charge. [True]
 Protons are in the nucleus of an atom. [True]
Neutrons are found in shells around the nucleus. [False]
Support students by putting a labelled diagram of the atom on the board for them to refer to. Extend students
by asking them to reword the false statements, so that they are true. (5 minutes)
Definitions – Give the students the definitions on the board. Students should match each
definition with a key word:
 A positive particle in an atom’s nucleus. [Proton]
 A neutral particle with a relative mass of 1. [Neutron]
 The subatomic particle that is found in energy levels. [Electron]
 The number of protons in an atom. [Atomic number or Proton number]
 The number of protons and neutrons in an atom. [Mass number]
Students could then be asked to draw a diagram of an atom and label it to demonstrate all these key
terms. (10 minutes)
Main
The structure of the atom can be summarised in a spider diagram. Encourage the students to include
information about atomic number, mass number, subatomic particles. Students first met the terms
‘mass number’ and ‘atomic number’, as well as the structure of the atom in C1 Chapter 1.
Later in the lesson, this spider diagram could be extended to include isotopes and uses of isotopes.
Students could be asked to include a key in their diagram. For example, use specific colours for key terms:
red – proton, green – neutron, blue – electron, orange – atom, purple – isotope.
Students need to be able to use the periodic table to work out the number of each subatomic particle
in an atom. With a question and answer session, draw out how the periodic table can be used to
supply information about an atom.
Show the students how to calculate the number of each subatomic particle using mass number and
proton number.
Then ask the students to design a table to record the number of each subatomic particle in the first 20
elements. Then ask them to complete their table.
Introduce the students to isotopes with the examples given in the Student Book.
Plenaries
Association – Split the class into pairs. Students should face their partners. All students on the right
should start first, saying a word or phrase about the lesson. Then the next person says another
fact/key word based on the lesson. The activity swaps between partners until all the facts are
exhausted. If a student hesitates or repeats previous statements, then they have lost the association
game. (5 minutes)
Think – On the board, write the symbol for carbon-12 and carbon-14 isotopes. Ask the students to
use the periodic table and their knowledge of isotopes to list all the similarities between the atoms
and all their differences. [Similarities – same number and arrangement of electrons, same number of
protons in the nucleus, same chemical properties, same atomic number. Differences – different
number of neutrons in the nucleus, different mass numbers, different physical properties.] You could
support students by using hydrogen isotopes and having the structure, including the subatomic
particles of the three isotopes on the board. Extend students by asking them to draw the structures of
the isotopes of carbon. They could be asked to find out about the third isotope of carbon: carbon-13
and also draw this structure. (10 minutes)
Support
Some students will struggle with the
vocabulary used in this topic area. Write a
list of key words on to the board so they can
use these throughout the lesson. You may
wish to further support them by also having
the definitions next to each word.
Extend
Ask students to draw the structure of the two
chlorine isotopes (35Cl and 37Cl). They could
then try to explain why the relative atomic mass
of chlorine is 35.5.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.2 Masses of atoms and
moles
Pages 110–111
Learning objectives
Learning outcomes
Specification link-up
Students should learn:
 that the masses of atoms can
be compared by their relative
atomic masses
 that carbon-12 is used as a
standard to measure relative
atomic masses [HT only]
 that the relative formula mass
of compounds can be
calculated.
Most students should be able to:
 give a definition of relative formula
mass
 calculate relative formula mass if the
formula and the relative atomic
mass are given
 state what a mole is.
Some students should also be able to:
 give a full definition of relative
atomic mass. [HT only]
The relative atomic mass of an element (Ar)
compares the mass of atoms of the element with
the 12C isotope. It is an average value for the
isotopes of the element. [C2.3.1 e)] [HT only]
The relative formula mass (Mr) of a compound is
the sum of the relative atomic masses of the
atoms in the numbers shown in the formula.
[C2.3.1 f)]
The relative formula mass of a substance, in
grams, is known as one mole of that substance.
[C2.3.1g)]
Kerboodle
Lesson structure
Support, Extend and Practical notes
Starters
Demonstration – Have a mole of different elements premeasured in sealed containers, e.g. 12 g
of carbon, 24 g of magnesium. Allow the students to handle different samples. Explain to these
students that all these examples have something in common – but what? Encourage the students
to use the Student Book and discuss in small groups how these samples relate to each other.
They should realise that these are all examples of moles. Then ask students to raise their hands if
they can tell you the mass of, e.g. 1 mole of carbon (and hold up the sample), etc. Repeat for all
the samples that you have. (5 minutes)
Word search – Give the students a word search for the key words that they will be using in the
lesson: ‘relative’, ‘atomic’, ‘mass’, ‘formula’, ‘mole’, ‘atom’. Instead of just asking the students to
find the words, give clues. Support students by giving them both the clues and the key words.
They can then match them up before finding the key words in the word search. Extend students
by asking them to write a definition for each of the keywords. (10 minutes)
Main
Higher Tier students should understand that the masses of atoms are compared to 1/12 of
the mass of a carbon-12 isotope. It is also worth noting that many periodic tables give the
mass number of the most common isotope rather than the relative atomic mass based on
natural proportions of different isotopes.
Students need to be able to obtain Ar from the periodic table or a data book and calculate
Mr. Give the students a set of cards showing the symbols of different elements (single
atoms and molecules) and compound formulas. Write numbers that represent Ar or Mr on
separate cards.
Students should complete calculations and match the formula with its Ar and Mr. They
should also decide if the number represents Ar or Mr. This could be made into a
competition, by splitting the class into small teams.
Students need to be able to define the key terms: ‘relative atomic mass’ [HT only for full definition
including the use of carbon-12 as a standard], ‘relative formula mass’ and ‘moles’.
Give the students a template of a cube. They should write definitions of relative atomic
mass, moles and relative formula mass on three faces. They should include a worked
example of calculations relating to this topic on each of the remaining faces, using lots of
colours. Then they cut out the template and score the lines to create sharp folds and stick
the cube together.
Plenaries
Difference – Ask the students to explain the difference between the symbols Ar and Ar.
Choose a volunteer to explain to the class. [Ar is the symbol for the element argon, Ar is
the shorthand notation for relative atomic mass]. (5 minutes)
In the bag – Put the key words: ‘relative atomic mass’, ‘relative formula mass’ and ‘mole’
into a colourful bag. Ask for three volunteers to come to the front and remove a word in
turns. After they have removed their word, they should show the class the word and
explain what it means. You should interject with a question-and-answer session to help
rectify any misconceptions. Support students by giving them a list of definitions on the
board: the student chooses a word and then looks at the definition, picking the one they
think the word matches. Extend students by listing words under the key word that they
cannot use in their explanation. (10 minutes)
Support
Provide students with a precut-out cube template that is
also ready scored. To help further, add some
information already on it, for example the titles or prose
with missing words.
Extend
Ask students to work out the formulae of compounds
(either by using the Student Book or using dot and
cross diagrams). Then encourage them to use the
periodic table to get the Ar before working out the Mr.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.3 Percentages and
formulae
Pages 112–113
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn that:
 how to calculate the
percentage of an element in
a compound from its formula
 how to calculate the
empirical formula of a
compound from its
percentage composition.
[HT only]
Most students should be able to:
 calculate the percentage composition
of an element in a compound.
Some students should also be able to:
 calculate the empirical formula of a
compound if the percentage
composition of the elements is given.
[HT only]
The percentage of an element in a
compound can be calculated from the
relative mass of the element in the formula
and the relative formula mass of the
compound. [C2.3.3 a)]
The empirical formula of a compound can
be calculated from the masses or
percentages of the elements in a
compound. [C2.3.3 b)] [HT only]
How Science Works:
You need the right
formula
Bump up your grade:
Chemical
calculations
Lesson structure
Support, Extend and Practical notes
Starters
Measurement – Show the students different mass values on balances. Ask them to note
the values shown to the nearest two decimal places. Read out the answers and ask the
students to put up their hands if they got them all right, one wrong, two wrong, etc.
Approach students who have been having difficulty and help them to see why they
recorded the wrong answer. Support students by a worked example on the board to help
them truncate data. Extend students by showing them different methods of measuring
mass (bathroom scales, kitchen scales, top pan balance, accurate level balance) and
using these to measure the mass of the same item. Ask students to comment on reliability
and accuracy of the results and to suggest why truncation is useful. (5 minutes)
Concept cartoon – Show the students a concept cartoon to highlight the conservation of
mass theory. Ask them to discuss the cartoon in small groups. Then feed back to the rest
of the class. Address any misconceptions at this stage. (10 minutes)
Main
Calculations often involve a set order of steps. Choose an example question to calculate
the percentage composition of an element and write out each step onto separate cards.
Encourage the students to order the cards and copy out the worked example correctly.
Then give the students other examples to work out themselves.
The same idea can be repeated with Higher Tier students, but for generating a formula of a
compound from percentage composition data can be used instead. [HT only]
Give the students two flash cards. On one side of the first card they should write how to
calculate the percentage composition of an element in a compound. On the reverse, they
should make up some questions of their own.
Higher Tier students should write how to generate the formula on one side of the second
card, and some questions on the reverse. [HT only]
The students can then work out the answers and write them upside down on their revision card.
In pairs, students swap their revision cards, tackle each other’s questions and check their
answers. They should be encouraged to feed back any problems that they are having to
their partner.
Higher Tier students could experimentally determine the formula of magnesium oxide. This
requires them to be able to read a balance accurately to two decimal places. They should design
their own results table and show all their working to generate the formula from their experimental
data. They should calculate the mass of magnesium used (mass of initially full crucible minus
mass of empty crucible). Then they should calculate the mass of oxygen in the compound (mass
of crucible after heating minus mass of initially full crucible). [HT only]
Once the mass of each element in the compound is known, the formula can be calculated
as detailed in the Student Book. [HT only]
Plenaries
Calculation – Ask the students to calculate the percentage composition of each element in
ammonia. They should recall the formula of ammonia from previous work. [N = 82 per cent;
H = 18 per cent.] Support students by giving them the formula of ammonia and the Ar for H
and N. Extend students by asking them to calculate the mass of nitrogen in 25 g of
ammonia. [20.5 g.] (5 minutes)
On the spot – Ask for a volunteer to stand at the front of the class, and give the other
students scrap paper. Read out questions to the volunteer, who should give an answer.
The other students then write numbers and hold them up to show how strongly they agree
with the answer. (If they strongly disagree they hold up 1; if they strongly agree they hold
up 10, for example.) You could reveal the true answer. (10 minutes)
Support
Some students will struggle with calculations. These
students will benefit from having a worked example that
they can refer to with the steps explicitly shown.
Thought processes could be written in prose as
reminders. Provide a writing frame that follows the
worked example can also help to formalise the working.
Extend
Give students more complex empirical formula
questions to attempt, e.g. P2O5.
Practical support
Determining the formula of magnesium oxide
Equipment and materials required
Small strips of magnesium ribbon (less than 2 cm
length), ceramic crucibles and lids, Bunsen burner and
safety equipment, tongs, pipeclay triangle, tripod,
accurate balance, eye protection.
Details
Students should note the mass of the crucible and lid.
They should twist the magnesium ribbon into a coil
shape and put it into the crucible. They should note the
new mass of the crucible, put it onto the pipeclay
triangle and heat it strongly in a blue Bunsen flame,
lifting the lid gently and occasionally to boost the
oxygen flow. They must not lift the lid up high, as some
of the product will be lost as white smoke. When the lid
is lifted and there is no white light, then the reaction is
complete. Then they turn off the Bunsen and allow the
crucible to cool, noting the mass of the crucible at the
end of the reaction. [HT only]
Safety: Eye protection should be worn throughout the
reaction and students should be warned that the
crucible will retain heat for a surprising amount of time
and may crack. CLEAPSS Hazcard 59 – Magnesium
ribbon.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.4 Equations and
calculations
Pages 114–115
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that balanced symbol equations show
the relative numbers of molecules of
reactants and products in a reaction
[HT only]
 that balanced symbol equations can be
used to calculate the masses of
reactants and products. [HT only]
Most students should be able to:
 interpret how many moles of
reactants/products are shown in a
balanced symbol equation [HT only]
 balance symbol equations [HT only]
 use a balanced symbol equation to
calculate the mass of reactants or
products. [HT only]
The masses of reactants and
products can be calculated from
balanced symbol equations.
[C2.3.3 c)] [HT only]
Maths skills:
Equations and
calculations
Extension:
How much?
Lesson structure
Support, Extend and Practical notes
Starters
Multiple-choice – Give each student three coloured flashcards, e.g. blue, green and red.
Then create a few multiple-choice questions, one per slide on PowerPoint, with three
answers, each one written in a different colour to match the flash cards. This could also be
achieved using Word or whiteboard software. Then show each question in turn and the
students hold up the card that represents the answer they think is correct. (5 minutes)
Chemical equations – Ask the students to complete the following chemical equations:
1 Mg + [O2] → 2MgO
2 CH4 + O2 → [CO2] + 2H2O
3 Zn + CuSO4 → [Cu] + [ZnSO4]
4 [NaOH] + HCl → NaCl + H2O
Then students could turn these into balanced symbol equations. Support students by giving
them the missing words. To extend this activity, you could ask the students to say what type
of reaction each of the above represents [1 oxidation; 2 combustion/oxidation; 3
displacement; 4 neutralisation]. (10 minutes)
Main
Students may have been introduced to balancing symbol equations in Key Stage 3 and will
have covered it during their studies of C1. You may wish to return to the familiar equation for
the oxidation of hydrogen, which is often used to demonstrate balancing equations. Advance
students by explaining that the numbers that are used to balance the equation can be
thought of as a ratio. Therefore two molecules of hydrogen will react with one molecule of
oxygen to make two molecules of water. However, as this is a ratio, we can also say that two
moles of hydrogen will react with one mole of oxygen to make two moles of water. You may
then wish to work through the calculation example given in the Student Book for the reaction
between hydrogen and chlorine.
Students need to be able to work out the masses of different substances in balanced symbol
equations. Create a card loop by drawing a rectangle 10 cm by 15 cm. Draw a dotted line to
make a square 10 cm by 10 cm. In the square, write out questions that involve balancing
equations and calculating reacting masses. Then, in the 5 cm by 10 cm rectangle, write an
answer (not one that matches the question on the card). Ensure that the questions match
answers on other cards so that a loop is made. Give the question loop set to small groups of
students and allow them to complete the card sort. Then encourage the students to pick two
of the questions and answers to copy into their book, but show their working out stage by
stage (as demonstrated in the Student Book).
Split the class into pairs, and on separate pieces of paper write enough calculation questions
for one per group. Give out the questions and allow the students to start to answer for 3
minutes (timed using a stopwatch). Then ask the students to hand the paper to another
group. Give the next group 3 minutes to correct the previous work and then continue with the
answer. Repeat this a number of times until there has been enough time for the answers to
be completed. Then return the paper back to the ‘owners’ where they should copy up the
question and the full answer.
Plenaries
Reflection – Ask students to think about the objectives for today’s lesson. Ask them to consider if
they have been met, and discuss this in small groups. Ask a few groups to feed back to the rest of
the class, explaining how they know that they have met the objectives. (5 minutes)
AfL (Assessment for Learning) – Give students some calculations but, instead of tackling
the questions, encourage them to create the mark scheme. Ask the students to work in small
groups discussing the questions and devising the marking points, and include alternative
answers that could still be given credit, and those that definitely should not be awarded
marks. This activity can be differentiated by using questions from the tier of entry students
are being entered for. (10 minutes)
Support
Some students will find the calculations difficult. Give
them half-finished calculations, where they need to
add numbers into the working out to generate the
answers. Peer mentoring could also be used, where
the students are split into pairs, with Higher Tier
students supporting Foundation Tier students.
Extend
Give students more complex symbol equations to
complete calculations. Include data that would
encourage students to truncate answers.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.5 The yield of a
chemical reaction
Pages 116–117
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that the amount of product
made can be expressed as
a yield
 how to calculate percentage
yield [HT only]
 that it is important to
maximise yield in industrial
processes and reduce the
waste of energy.
Most students should be
able to:
 give a definition of yield
 list factors that affect yield
 describe why sustainable
production in industry is
important.
Some students should also
be able to:
 calculate percentage yield.
[HT only]
Even though no atoms are gained or lost in a chemical
reaction, it is not always possible to obtain the calculated
amount of a product because:
 the reaction may not go to completion because it is
reversible
 some of the product may be lost when it is separated
from the reaction mixture
 some of the reactants may react in ways different from
the expected reaction. [C2.3.3 d)]
The amount of a product obtained is known as the yield.
When compared with the maximum theoretical amount as
a percentage, it is called the percentage yield. [C2.3.3 e)]
Evaluate sustainable development issues relating the
starting materials of an industrial process to the product
yield and the energy requirements of the reactions
involved. [C2.3]
Viewpoint:
Making chemistry
better
Practical:
Calculating the
percentage yield
of a reaction
Lesson structure
Support, Extend and Practical notes
Starters
Mirror words – Ask the students to work out these key words, which will be used in the
lesson:
 stnatcaer [reactants]
 stcudorp [products]
 dleiy [yield]
 egatnecrep [percentage]
 noitaluclac [calculation] (5 minutes)
Definition – Ask the students to explain what a yield is. If they are a Higher Tier, ask how it
can be calculated. Support students by encouraging them to use the Student Book to help
them. Extend students by asking them to look at the worked example and find the actual,
theoretical and percentage yields (including the units). (10 minutes)
Main
Split the class into teams of about five students. Prepare ten questions for each group, they could
be written on colour-coded paper. The questions should be face-down on a front desk. A volunteer
from each group should retrieve their first question and take it back to his or her table. If the students
are Higher Tier candidates, the team should complete the calculation. As soon as they have an
answer, they take it to you to be checked. If they are correct, then they can get their next question. If
they are incorrect, they should try again, with help where needed.
Ask Higher Tier students to look carefully at the worked example for calculating the
percentage yield. Ask them to draw two flow charts to show the steps of how to complete
these calculations. Then give the students a number of questions they can answer using
their flow charts to help them.
Discuss the importance of sustainable production. Students can then list the advantages.
Plenaries
Steps – Write a question on the board that involves the calculation of a yield (an example
could be used from the Student Book). Put each separate number or mathematical
procedure on to separate sheets of A3 paper and arrange them on the floor in the wrong
order. Ask for a volunteer to stand on the starting number and move on to the next sheet
physically, showing the order of the calculation. Encourage the students to describe how
they would do the calculation as they stand on the different pieces of paper. Support
students by asking them to work in small groups to order the steps. Extend students by
having parts of the equation missing. Students should therefore not only order the steps but
also complete them. (5 minutes) [HT only]
What’s the question? – Give students an answer such as yield, mass lost, 100 per cent
yield, reversible reaction, etc. Encourage them to work in small groups to generate questions
that match the answer given. You could support students by listing questions on the board:
they could then choose the question that best fits their answer. For Higher Tier students, you
could include answers to calculations of percentage yield. (10 minutes)
Support
Use a flow chart to show the steps that cause yield to
be reduced in a chemical process. The different steps
in the flowchart, such as transferring glassware etc.,
could be given to the students. They could then cut
them out and stick them in the correct order into a
pre-drawn flow chart outline.
Extend
Ask students to complete yield equations that require
manipulation of units, e.g. data given in tonnes or kg.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.6 Reversible reactions
Pages 118–119
Learning objectives
Learning outcomes
Specification link-up
Students should learn:
 that reactions can be
reversible
 how reversible reactions can
be represented.
Most students should be able to:
 define a reversible reaction
 recognise a reversible reaction from its
word or symbol equation.
Some students should also be able to:
 explain what a reversible reaction is,
giving an example.
In some chemical reactions, the products of the
reaction can react to produce the original
reactants. Such reactions are called reversible
reactions and are represented:
A+B
Kerboodle
C+D
For example: ammonium chloride
ammonia + hydrogen chloride. [C2.3.3 f)]
Lesson structure
Support, Extend and Practical notes
Starters
Card sort – Create a card sort for the students to match the key words with
their definitions. Put the cards into envelopes and give each pair of students a
set to sort out on their desk. Then ask students to pick three new words and
write them in their book, including the definition. Reactants – starting
substances in a chemical reaction. Products – substances left at the end of a
chemical reaction. Reversible reaction – where the reactants make the
products and the products make the reactants. Indicators – chemicals that
react with acids and alkalis to make different-coloured compounds. Chemical
reaction – a change in which a new substance is made. Support students by
encouraging them to use the Student Book to help them. Extend students by
encouraging them to use the Student Book to give examples of each of the key
words. (5 minutes)
Reflection – Ask students to draw a table with three columns headed ‘What I
already know’, ‘What I want to know’, ‘What I know now’. Encourage the
students to look at the title of the page and the objectives. Then ask them to fill
in the first column with facts they already know about the topic, presented as
bullet points. Then ask them to think of questions that they think they need to
have answered by the end of the lesson and note these in the second column.
(10 minutes)
Main
Students will be familiar with the use of indicators from their work on acids and
alkalis at Key Stage 3. The colour changes produced by indicators are
reversible reactions. Students could find out (experimentally or using
secondary resources) the colour changes of different indicators in
acidic/neutral/alkaline solutions.
Heating ammonium chloride causes thermal decomposition to form ammonia
and hydrogen chloride. This reaction can be completed experimentally in the
lab by heating ammonium chloride in a boiling tube with a loosely fitted plug of
mineral wool, then relating this to reversible reactions. Encourage the students
to focus their attention on the cool part of the boiling tube. Ask them to explain
in the form of a flow chart what is happening in the boiling tube.
Plenaries
True or false – On separate sheets of sugar paper, write the words ‘true’ and
‘false’. Then stick them on opposite sides of the classroom. Read out the
statements below. Students should stand next to the wall to represent their
answer. If they don’t know, they should stand in the centre of the room.
 A double-headed arrow in an equation shows that it is a non-reversible
reaction. [False]
 In a reversible reaction, reactants make products and products make
reactants. [True]
 All chemical reactions are reversible. [False]
 Indictors react with acids but not with alkalis. [False]
 The decomposition of ammonium chloride is a reversible reaction. [True]
Support students by giving them statements on a card and they discuss them
in small groups before the movement commences. Extend students by asking
them to rephrase the incorrect statements so that they are correct. (5 minutes)
Reflection – Ask students to review their starter table (‘Reflection’) and use a
different colour pen/pencil to correct any misconceptions from the start of the lesson.
Then ask the students to answer the questions they posed. If they can’t, encourage
them to talk in small groups, consult the Student Book and, if necessary, ask you.
Finally, students should record, in bullet-point format, any other facts that they have
picked up during the lesson, in the last column. (10 minutes)
Support
You could take the reactants and products in a reversible reaction to
form a flow chart to explain the term ‘reversible reaction’. This could be
made into a ‘cut-and-stick’ activity which would generate a cycle.
Extend
Ask students to find examples of reversible reactions that they
benefit from in everyday life, e.g. oxygen binding to haemoglobin in
their blood.
Practical support
Litmus
Equipment and materials required
A test tube, test tube holder, red or blue litmus solution, 1.0
mol/dm3 hydrochloric acid, 0.04 mol/dm3 sodium hydroxide, 2 ×
dropping pipettes, eye protection.
Details
Put a few drops of litmus indicator into a test tube. Add a few drops
of acid and observe. Add a few drops of alkali and observe. Repeat
to demonstrate the reversible reaction.
Safety: CLEAPSS Hazcard 47A Hydrochloric acid – corrosive.
CLEAPSS Hazcard 31 Sodium hydroxide – corrosive. Both
solutions at the concentrations used are low hazard, but eye
protection should be worn throughout the experiment.
Heating ammonium chloride
Equipment and materials required
A boiling tube, boiling tube holder, Bunsen burner and safety
equipment, mineral wool, spatula, ammonium chloride, eye
protection.
Details
Put about half a spatula of ammonium chloride into a boiling tube and
insert a mineral wool plug at the top. Gently heat in a Bunsen flame.
Safety: Eye protection should be worn at all times. As acidic
hydrogen chloride gas and alkaline ammonia gas are produced, the
mineral plug must be used and the reaction should be carried out in
a well-ventilated room. CLEAPSS Hazcard 9A Ammonium chloride
– harmful.
Heating copper sulfate
Equipment and materials required
A boiling tube, boiling tube holder, Bunsen burner and safety
equipment, spatula, hydrated copper sulfate, wash bottle, eye
protection.
Details
Put about half a spatula of hydrated copper sulfate into a boiling
tube and heat gently on a Bunsen flame until the colour change to
white is complete. Remove from the heat and allow the boiling tube
to cool. Then add a few drops of water and observe.
Link
This reaction will be studied in the next chapter in terms of the
energy changes involved in reversible reactions.
Safety: Be careful to allow the boiling tube to cool before adding water
as the glass could crack. Eye protection should be worn throughout this
experiment. CLEAPSS Hazcard 27C Copper sulfate – harmful.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C2 3.7 Analysing
substances
Pages 120–121
Learning objectives
Learning outcomes
Specification link-up
Students should learn:
 how to detect and identify
artificial food colourings
 that there are advantages
of using instrumental
analysis.
Most students should be able to:
 describe an experiment to separate
coloured additives
 list advantages of modern analysis
techniques.
Some students should also be able to:
 explain in detail how coloured food
additives can be detected and
identified using paper
chromatography.
Chemical analysis can be used to identify additives
in foods. Artificial colours can be detected and
identified by paper chromatography. [C2.3.2 b)]
Elements and compounds can be detected and
identified using instrumental methods. Instrumental
methods are accurate, sensitive and rapid and are
particularly useful when the amount of a sample is
very small. [C2.3.2 a)]
Controlled Assessment: AS4.5 Analyse and
interpret primary and secondary data. [AS4.5.4 c) d)]
Kerboodle
Lesson structure
Support, Extend and Practical notes
Starters
Original additive – Show students a picture of some spices and salt fish.
Ask students to suggest their connection [food additives]. Spices are used
to improve the taste, colour and smell of a food and salt can act as a
preservative. Ask students to suggest any examples of modern-day
additives that would not have been available 200 years ago (e.g. MSG).
(5 minutes)
Dominoes – Give the students a card sort with the key words: ‘preserve,
food additive, solvent, chromatography’ written on. Each card should also
have a definition. Students should work in pairs to match the ends up, as in
a domino game. (10 minutes)
Main
Food colourings are often added to food to make them more appealing.
Colours can be added to sweets and savoury foods. Students can
complete chromatography experiments of different food colourings. Then
the chromatograms could be stuck into their book and conclusions drawn
from their results. Students can evaluate the reproducibility, repeatability
and validity of the experiment as a means of detecting and identifying
artificial colourings.
If chromatography is being used to identify additives, then it is essential for
the conditions to be the same. This allows test chromatograms to be
compared with standard ones. You may wish to allow students to make
‘standard’ chromatograms for food colourings, then analyse a mystery food
colouring (prepared in advance by mixing some of the food colouring
available to the students) to determine which food colourings are present.
Chromatography can be completed using a variety of different materials
such as TLC plates. You may be able to make chromatograms using
different stationary phases and solvents.
Explain to students that using instruments for analysis has advantages and
disadvantages. Give the students the six statements as detailed in the
bullet points featured in the Student Book. Students should cut out and
stick each statement into a table with two columns, headed ‘Advantages’
and ‘Disadvantages’ respectively. Support students by encouraging them
to use their Student Book to help them. To extend students, ask them to
consider why it has taken time to develop instrumental analysis [it is
dependent on technological development].
Plenaries
AfL (Assessment for Learning) – Ask students to compare
chromatograms produced – which group produced the best one for
analysis purposes? Take a class vote on the best chromatogram and why.
(5 minutes)
Explain – Ask the students to explain how chromatography works. Then
pick three students randomly from the register to read their explanations.
Reward the best explanation. Support students by giving them statements
in the wrong order to explain chromatography. Extend students by
suggesting other applications for chromatography. (10 minutes)
Support
You could use a simpler method of creating a chromatogram. An easier
way to generate a chromatogram is to give the students a disk of filter
paper. Ask them to use a paintbrush to put a sample of a food colouring
into the centre. Then cut a wick (a wedge shape towards the centre).
Balance the paper over a beaker with water in it. The wick must be
submerged. The colours will then separate into rings.
Extend
Encourage students to find out more about the stationary and mobile
phases in paper chromatography and use them to give a more detailed
explanation of chromatography.
Practical support
Detecting dyes in food colourings
Equipment and materials required
Different food colourings, capillary tubes, boiling tube, boiling tube
rack, ruler, pencil, strips of chromatography paper that fits into the
boiling tube.
Details
Draw a pencil line 2 cm from the bottom of the chromatography paper.
Draw three pencil crosses on the base line, an equal distance apart.
Dip a clean capillary tube into a food colouring. The colour will suck into
the tube. Gently dot one of the crosses, trying to add only a small
amount of colouring. Repeat with two further colours on the remaining
crosses. Put a small amount of water in the boiling tube (about 1 cm
deep). Lower the chromatography paper into the tube and place in the
rack. Leave the chromatogram to develop, until the solvent line is past
the last separated colour. Try not to move the chromatograms while
they develop or it will not be easy to compare them. Students will see
which colourings were pure substances and which were mixtures of
dyes, and can list the component colours in any mixtures.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Chemistry
C3 3.8 Instrumental analysis
Pages 122–125
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that gas chromatography
can be used to separate
compounds
 that mass spectrometers
can be combined with gas
chromatography to identify
the components in a
mixture.
Most students should be able
to:
 describe the use of gas
chromatography linked with
mass spectrometry to
identify what is in a mixture.
Some students should also be
able to:
 explain in detail the
technique of gas
chromatography – mass
spectrometry
 explain how mass
spectrometry is used to
determine relative molecular
masses. [HT only]
Elements and compounds can be detected and identified
using instrumental methods. Instrumental methods are
accurate, sensitive and rapid and are particularly useful
when the amount of a sample is very small. [C2.3.2 a)]
Gas chromatography linked to mass spectroscopy (GCMS) is an example of an instrumental method: gas
chromatography allows the separation of a mixture of
compounds. The time taken for a substance to travel
through the column can be used to help identify the
substance. The output from the gas chromatography
column can be linked to a mass spectrometer, which can
be used to identify the substances leaving the end of the
column … . [C2.3.2 c)]
… The mass spectrometer can also give the relative
molecular mass of each of the substances separated in
the column. [C2.3.2 c)] [HT only]
Interactive activity:
How much?
Revision podcast:
Mass and atoms
Test yourself: How
much?
On your marks:
How much?
Examination-style
questions: How
much?
Answers to
examination-style
questions: How
much?
Lesson structure
Support, Extend and Practical notes
Starter
Think – Show students an image of a science lab 100 years ago and a modern science
laboratory. Ask students to think about why instrumental analysis has only recently
developed. Allow students to discuss their ideas as a class. (5 minutes)
Main
Instrumental analysis is very precise. It gives similar readings every time the same sample
is analysed.
Gas chromatography is often used with mass spectrometry. A sample made of a mixture of
chemicals is injected into a gas chromatography machine in order to separate the mixture.
The separate samples then go into a mass spectrometer for identification.
Ask students to imagine that they have been commissioned to write an instruction leaflet to
be in the packaging of a GC-MS machine. You could show some example leaflets such as
those that are supplied with toasters or TVs. Students should include a schematic diagram
of how the machine works. They could create a flow chart to detail the stages involved in
separation and identification.
Ask students to work in pairs to compare their leaflets. Students should comment on the
science content, choice of language, activity and presentation, giving a mark out of 10 for
each of these aspects. Then they can award an overall mark out of 40. They could make
amendments as homework.
Plenaries
Persuade – Ask students to work in small groups, and imagine that they are research
chemists who have made a new fertiliser. Each group should make a persuasive argument
for a board of directors on why they should finance the use of instrumental analysis
technique rather than using traditional laboratory techniques. Support students by giving
them some statements that could provoke discussion. Extend students by asking some of
them to role play the board of directors and encourage them to be biased against using the
techniques. (5 minutes)
Paper round – Give each student a piece of A4 paper. Students should work in groups of
six. Ask them to write an example of instrumental analysis at the top of the paper, then fold
the paper over and pass to the student at the right. Then ask the next person to write, on
the folded paper from another student, one new fact that they have learned. Again fold
over the paper and pass it to the right. Ask the students to continue to fold over and pass
the paper after writing a revised fact, an advantage of instrumental analysis, a
disadvantage of instrumental analysis and one use of mass spectrometry. After the sixth
paper move, ask each student to unfold the paper and read what has been written. If time
allows, ask a few students to share the work from their paper. Examination technique can
be highlighted from this exercise, as some students should have answered in sentences,
whereas others may have used key words that might be ambiguous. (10 minutes)
Support
Refer to chromatography as detailed in C2 3.7
Analysing substances as a scaffold to understanding
gas chromatography (GC).
Extend
Give students simple mass spectra and a list of
compounds. They could then try to match the
compound to the spectra. N.B. Students do not need to
know about fragmentation patterns.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011