Download C2.3 Atomic Structure, Analysis and Quantitative Chemistry

Y11 2.3 Atomic Structure, Analysis and Quantitative chemistry
Where to find resources:
 Look in k:\staff only\science\chemistry\AQA GCSE Chemistry Here you will
find the resources mentioned here and the learning objective sheets.
 Big red folder in prep room with a series of worksheets and practicals.
 Yellow folder in prep room with practicals for C2, each one allocated a
code to make ordering them easier.
 Longman p118-133 and Nelson Thorne textbooks p138-155 are available.
There are lots of good questions
 There is a teacher guide for the GCSE chemistry course in the prep room, it
is a yellow book giving a good deal of information about the course and
suggested teaching order broken down into lessons. It looks like this:
C2.3 Atomic Structure, Analysis and Quantitative Chemistry
Learning outcomes
Subject Area
Foundation
1 Atomic Structure



2 Analysing
substances



Know the use of mass number and
atomic number
Know the mass of each sub atomic
particle.
Atoms of the same element with a
different number of neutrons are
known as isotopes
Elements and compounds can be
detected using instrumental methods
Intermediate



Chemical analysis can be used to
identify additives in foods

gas chromatography allows the
separation of a mixture of
compounds



3 Quantitative
Chemistry

Know that is not always possible to
obtain the calculated amount of
product in a chemical reaction
because:
(a)
The reaction is reversible and
does not go to completion
(b)
Some of the product is lost
when it is separated from the
reaction mixture
(c)




Some of the reactants will react
in different ways to the
expected reaction
The amount of product is known as
the yield

The relative atomic mass(Ar) of an
element compares the mass of
atoms of that element with the mass
of a126C isotope
The Ar value is an average value of
the isotopes of an element
Instrumental methods are accurate,
sensitive and can be carried out
rapidly
Higher



Instrumental methods are useful
when the amount of sample is small
The relative formula mass of a
substance in grams is known as one
mole of that substance
The relative formula mass (Mr) is
the sum of the relative atomic
masses of the atoms shown in the
formula that substance
The mass spectrometer can give
the relative molecular mass of
each of the substances from the
column
Paper chromatography can be used
to identify artificial food colours
The time taken for a substance to
travel through the column can be
used to identify the substance
The output from a gas
chromatography column can be
inked to a mass spectrometer to
identify the substances
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
.When the actual yield is compared
to the theoretical yield it is known as
the percentage yield
Some chemical reactions are
reversible, in which the products of
the reaction can react to produce the
original reactants.
These reactions are represented by
an equation such as
:
A+B
C+D



Be able to calculate empirical
formula from the masses or
percentages of the elements in a
compound
Be able to calculate the masses of
individual products in a chemical
reaction from the mass of a given
reactant and the balanced
equation
Calculate percentage yield from
Actual yield
x 100%
Theoretical yield
Overview
This topic covers some very fundamental ideas in chemistry. The first part is a recap of
atomic structure and the nature of sub- atomic particles, particularly in terms of the mass
of these particles and the ideas of atomic number and Mass number. The idea of isotopes
and the definition of relative atomic mass (Ar) is now introduced. Higher candidates will
have to calculate the Mr for compounds from a given formula and the concept of the mole
is introduced.
The next part of the unit relates to analysis in terms of chromatography both paper and gas
chromatography. The idea of a mass spectrometer attached to a GC is used to reinforce the
idea that compounds can be identified from their Mr value, determined from the molecular
ion peak of a mass spectrometer trace for higher candidates
The last section is on quantitative chemistry and introduces the idea of various calculations
for higher tier with calculations on empirical formula as well as reacting mass calculations
and percentage yield
All candidates need to know that there are reasons why not all reactants are converted to
products as they could be lost in transfer, bi- products can be produced or that the reaction
is reversible
C2.3 - Atomic Structure, Analysis and Quantitative chemistry Lesson 1
Aims

Recap ideas from C1.1

Identify each of the three subatomic particles – protons, neutrons and electrons

Recall location, mass and charge of each of the three subatomic particles

Identify the numbers of protons, neutrons and electrons for each element in the periodic table
including the electron arrangement up to atomic number 20 – calcium

Identify the numbers of protons, neutrons and electrons for isotopes of a given element
Language and definitions
Term
Proton
Neutron
Electron
Nucleus
Shell /
energy level
Atomic
number
Mass
number
Isotope
Definition
A sub atomic particle with a mass of 1 and a charge of +1
A sub atomic particle with a mass of 1 and no charge
A sub atomic particle with no mass and a charge of -1
The centre of an atom where protons and neutrons are found
The location of an electron in an atom
Number of protons in an atom
Number of protons plus number of neutrons in an atom
Atoms of the same element with a different number of neutrons
Resources
Resource (type)
Description
Periodic table (WS)
A period table for use in GCSE
chemistry / science
C2.3Fundamentals (PPT)
Atomic Structure Card loop (WS)
L- C2 3.1c
Atomic Structure 1 and 2 (WS)
L C2 3.1 b and d
A WS which reviews the
properties and arrangement of
sub atomic particles first covered
in C1.1
A worksheet to practice
calculating the number of sub
atomic particles from the mass
number and atomic number and
demonstrate difference between
isotopes
Location
Electronic copy in folder
In resources folder
In resources folder
In resources folder
In resources folder
C -2.3 - Atomic Structure, Analysis and Quantitative chemistry Lesson 2
Aims

Use the term of relative atomic mass (Ar)

Understand that relative atomic mass compares the mass of atoms with the 12C isotope

Understand that the relative atomic mass is the average value for the isotopes of the element

Be able to calculate relative formula mass (Mr) of a substance using Ar for each element present in
the substance

Describe that the mass of one mole of a substance equals the M r in grams

Use the relationship mass = Mr x number of moles
Language and definitions
Term
Relative
atomic mass
(Ar)
Relative
formula
mass (Mr)
Mole
Definition
The relative mass of an atom of a given element compared to an atom of
the 12C isotope ( This value is an average which takes account of all the
isotopes of the element and their relative abundance
This relative mass of a substance is calculated by adding up the relative
atomic mass of each atom in the formula for the substance
The number of particles found in 12g of a of 12C atoms (6.02 x 1023)
Resources
Resource (type)
The relative mass of animals
L C2 3.1a
Relative masses (worksheet)
LC2 3.2a
Finding moles by weighing
(practical W/S)
L C2 3.2b
Using moles / Relative masses
and moles
(W/S)
L C2 3.2c and L C2.3d
Also echalk - moles
Description
This is a good introduction to
relative atomic mass particularly
for students who struggle with
abstract concepts
This is simply practice at
calculating Relative formula mass
If you have time this practical
breaks up these theory lessons
and may help some students
visualise the concept of a mole
These worksheets give plenty of
examples of questions which
allow students to practice
questions linking Mr and moles
The echalk animation makes a
good activity for whole class (a
good starter/plenary activity)
Location
In resources folder
In resources folder
In yellow chemical practicals
folder –
In resources folder
C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 3
Aims

Be able to complete reacting mass calculations (higher)

Work out the percentage of an element within a compound by its mass

Explain what the empirical formula of a compound is (higher)

Be able to calculate the empirical formula from the mass or percentages of the elements in a
compound
Language and definitions
Term
Empirical
formula
Molecular
formula
Definition
The simplest ratio of the relative number of atoms of each element in a
compound expressed as a formula
The formula of a compound which expresses the actual number of atoms of
each element within one molecule
Resources
Resource (type)
Empirical formulae 1 and 2
L C2 3.5b and c (W/S)
(Higher)
Reacting Mass calculations 1
and 2 (W/S)
L C2 3.3 a and b
Description
These are difficult questions
used to practice empirical
formula calculations and use
of moles
Plenty of quite difficult
calculations to work through
Location
In resources folder
In resources folder
C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 4
Aims

Explain why instrumental methods are used to analyse substances

Explain how food colourings can be analysed using paper chromatography

Describe how gas chromatography can be used to separate mixtures

(higher) describe how substances can be used using mass spectroscopy
Language and definitions
Term
Instrumental
techniques
Gas
chromatography
Mass
spectroscopy
Molecular ion
Definition
An automated method of analysing chemicals
A method of analysis that separates chemicals in a very small sample in
order to identify their constituents
Analytical technique that breaks up molecules into ions and measures their
mass/charge ratios
The ion formed when a molecule is passed through a mass spectrometer
that has not been fragmented
Paper
Analytical technique that that separates compounds by their relative speeds
chromatography in a solvent as it spreads through paper
Retention time
Time taken for a substance to reach the detector at the end of a gas
chromatography column
Resources
Resource (type)
C 2 3.6a Paper
Chromatography
(practical)
C2 3.6b Gas
chromatography (W/S)
C2 3.6c (Higher) Mass
spectroscopy
C2 3.6d(higher)
Instrumental analysis
of food
Description
A simple practical where the
food colourings are analysed
using paper chromatography
A simple worksheet which
shows the use of GC to
separate mixtures and shows
retention time
Powerpoint Chromatography
This worksheet shows some
examples of mass spectra and
the idea of molecular ion peak
but you do not need to know
about fragmentation peaks!
This worksheet is a good
round up for all the ideas used
in this analysis section and
Location
In yellow chemical practicals
folder –
In resources folder
GC/MS
http://alpha.chem.umb.edu/chemistry/ch361/G
C%20and%20GC-MS.ppt
In resources folder
In resources folder
In resources folder
revises all the important terms
C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 5 and 6
Aims

The amount of product obtained during a reaction is known as the yield

The maximum amount of product that can be formed is known as the theoretical yield

The percentage yield is = actual yield
x 100 %
theoretical yield

The reaction may not go to completion because it is reversible

Some of the product may be lost when it is separated from the mixture

Some of the reactants may in different ways to the expected reaction and therefore produce
different products
Language and definitions
Term
Actual yield
Theoretical
yield
Percentage
yield
Reversible
reaction
Definition
Actual yield of product obtained during a chemical reaction
Maximum yield obtainable in a chemical reaction based on the reacting
mass calculation
The yield expressed as a percentage of product obtained divided by the
theoretical yield x 100%
A reaction in which the products can re-form the reactants
Resources
Resource (type)
C2 3.4b Measuring a
percentage yield
/Practical
C2 3.4a Reversible
reactions / practical
Description
Location
This practical involves weighing Yellow practical folder
magnesium in a crucible and
then heating it to make
magnesium oxide and weighing
it to calculate percentage yieldneeds accurate balance
These 3 practicals show
Yellow practical folder
examples of reversible reactions
– some significant risk
assessment for these reactions