Chemistry Reference
In-Depth Information
16
Experimental chemistry
Objectives for experimental skills and investigations
Suggestions for practical work and assessment
Safety
Redox
Notes on qualitative analysis
Appearance or smell
Flame colours
Tests for aqueous cations
Tests for aqueous anions
Tests for gases
Safety
In the suggested practical exercises, materials are
used which, although familiar in many cases, are of
a potentially hazardous nature, and appropriate care
and precautions should be taken. We believe that
the experiments can be carried out safely in school
laboratories. However, it is the responsibility of the
teacher to make the final decision depending on the
circumstances at the time. Goggles should be worn at
all times. In certain cases disposable gloves and fume
cupboards will be required.
Teachers must ensure that they follow the safety
guidelines set down by their employers, and a risk
assessment must be completed for
any
experiment
that is carried out. Teachers should draw students'
attention to the hazards involved in the particular
exercise to be performed.
●
Objectives for
experimental skills and
investigations
The IGCSE chemistry syllabus suggests that students
should be able to:
1
know how to safely use techniques, apparatus
and materials (including following a sequence of
instructions where appropriate)
2
plan experiments and investigations
3
make and record observations, measurements and
estimates
4
interpret and evaluate experimental observations
and data
5
evaluate methods and suggest possible
improvements.
All candidates must take a practical paper based on
the criteria above. You must take one of the following
papers:
●
Paper 5 - Practical Test, or
●
Paper 6 - Alternative to Practical (written paper).
Some examples of exam style questions from Paper 6
are given on pp. 264-74. The practical assessment is
20% of the available marks.
Redox
The concept of redox, either in its elementary form
(that is, as the loss or gain of oxygen) or as electron
transfer, is a constant theme throughout the syllabus
and the associated practical work. The list suggests
plenty of varied examples, designated by
R
, to
reinforce the theory.
Chapter 1 The particulate nature of
matter
Solids, liquids and gases
●
A simple demonstration to illustrate the three states
of matter and their interconversions - ice, water
and steam.
●
Demonstrate the compressibility of gases and the
incompressibility of liquids by using a syringe to
show that the volume of a gas (e.g. air) decreases
with pressure whereas that of a liquid (e.g. water)
does not.
●
Suggestions for practical
work and assessment
The following list suggests practical exercises that
could be used to both support the assessment
objectives given above and enrich the study of
chemistry; in addition, it should suggest plenty of
opportunities for the enhancement and assessment
of practical skills. The list is neither exhaustive nor
prescriptive: the actual selection of practical work,
whether from this list or from elsewhere, has to be
governed by local factors such as the facilities available,
safety considerations and the ability of the class.
