Chemistry Reference
In-Depth Information
●
Diffusion of a coloured solute in water. A large
crystal of copper(ii)
ii
) sulfate is added to a measuring
cylinder of water and is observed over several days.
●
Illustrate the use of chromatography as a test of
purity and an analytical tool. Suitable examples
include coloured inks, food colouring, pigments
from flowers or grass, metallic cations and
identification of sugars. At least one exercise should
involve developing a chromatogram and at least
one should involve the measurement of
R
f
values.
Chapter 2 Elements, compounds and
experimental techniques
Elements
●
Display samples of as many elements as possible,
either on information cards or on a copy of the
Periodic Table. This is an effective observation
exercise.
●
Set up a circus of activities which includes both
collecting data from computers or data topics
(e.g. melting and boiling points and density)
and practical exercises on comparing electrical
conductivities. These activities will illustrate the
physical differences between metals and non-metals.
Gels, sols, foams and emulsions
●
Set up a circus of gels, sols, emulsions and foams, e.g.
'jelly', milk, pumice stone, polyurethane foam, bread,
emulsion paint, cola, hair cream, aerosol dispenser,
salad cream. A silica gel can be made from sodium
silicate and hydrochloric acid. Classify the examples
according to type of colloidal system.
●
Make a colloidal sol of iron(
iii
) hydroxide by
adding aqueous iron(
iii
) chloride to boiling water,
or a colloidal sulfur sol by adding dilute aqueous
sodium thiosulfate to hydrochloric acid. For both
of these sols, it can be shown that the solid phase is
not separated by filtration.
Compounds and mixtures
●
Demonstrate the combination of elements to form
compounds, for example magnesium and oxygen,
iron and chlorine, hydrogen and oxygen, zinc and
sulfur, carbon and oxygen, and aluminium and
iodine.
●
Demonstrate the iron and sulfur experiment
described in the text (p. 16).
Chapter 3 Atomic structure and
bonding
Ionic bonding
●
Look up the melting and boiling points of ionic
compounds in data topics.
●
Show that most ionic compounds dissolve in water.
●
Demonstrate that an ionic compound, potassium
iodide or lithium chloride, conducts electricity in
the molten state but not as a solid.
Separating mixtures
●
Filtration, decanting and centrifuging to separate a
solid from a liquid (p. 18).
●
Evaporation to obtain a solute from a solution
(p. 19).
●
Crystallisation of impure benzoic acid. Benzoic
acid is contaminated with a
trace
of a blue dye
and then dissolved in the minimum amount of
boiling water. Allow to cool and separate crystals
by filtration. The blue colour will have disappeared
or become fainter, showing that crystallisation has
removed the impurity.
●
Simple distillation to separate a solvent from a
solution (p. 20).
●
Separation of immiscible liquids using a separating
funnel (p. 20).
●
Fractional distillation of a mixture of ethanol
and water will separate two miscible liquids and
illustrates that an impure liquid does not boil
at a specific temperature but over a range of
temperatures (p. 21).
Covalent bonding
●
Look up the melting and boiling points of simple
covalent compounds in data topics.
●
Show that they are not good conductors of
electricity in the liquid phase - demonstrate this
with hexane, ethanol or phosphorus trichloride.
●
Show that graphite is both soft and a good
conductor of electricity.
●
Use a glass cutter to illustrate the hardness of
diamond.
Glasses and ceramics
●
Heat a piece of glass tubing to demonstrate that it
gradually softens, will bend and can be pulled into
a finer tube. These changes show that glass is a
supercooled liquid, not a solid.
