Aim To test water hardness
Equipment
Distilled water, dilute magnesium sulfate solution, solution of calcium hydrogen carbonate,
suspension of calcium carbonate in water, small chips of bath soap, shampoo, detergent, 5 test tubes, rubber stoppers to fit test tubes
Method
1 Put about 2 cm of distilled water and 2 cm of tap water
into two separate test tubes.
2 Put about 2 cm of each solution into the other test
tubes.
3 Add a small chip of soap to all five tubes and stopper
lightly.
4 Shake the tubes vigorously and watch for any lather that
forms.
5 Record your results in order from the solution that
produced the most lather (the softest) to the one that produced the least lather (the hardest).
6 Repeat the experiment but use a few drops of shampoo. 7 Repeat again with a few drops of detergent.
Questions
1 Describe what soap does in hard water.
2 Identify the solution that was the hardest. Justify your
answer.
3 Deduce whether the water showed any hardness when
it contained shampoo or detergent.
4 Outline the advantage of detergent over soap. 5 Design a test to see if temperature has an effect on
water hardness. Hold stopper and shake. stopper Look for lather. solution of different salts small chip of soap
Fig 2.5.6 Is the water hard or soft?
Chapter review
[Summary questions]
1 State an example of an alloy and its base metal. 2 State whether the additives in alloys are usually metals
or non-metals.
3 List the carbon content of:
a cast iron b tool steel c mild steel 4 State how many carats are in pure gold.
5 If gold is 18-carat, state the percentage of gold present. 6 State a use for each of these materials:
a aluminium d Duralumin g bauxite b zinc e bronze h celluloid c cast iron f haematite i Kevlar 7 State one example each of:
8 Identify a metal that is extracted by:
a electrolysis b smelting c roasting 9 List the ingredients for a blast furnace.
10 State the special name given to the corrosion of iron. 11 Outline what is meant by ‘anodised aluminium’. 12 List four properties of a thermosetting plastic.
[Thinking questions]
13 Rose-gold is a pink-gold colour. Propose a metal that
could be added to the base metal to create this colour.
14 It is thought that iron simply oozed out of the rocks
used to surround the cooking pits of ancient hunters.
Compare these conditions with those of a blast furnace. 15 Primitive prospectors found gold and silver before any
other metal. Explain why.
16 Salt is often used in Europe and North America to help
melt ice on roads. Their cars also rust more quickly than ours. Explain why.
17 Explain why stainless steel is ideal for use as
replacement bone (hips, tooth implants, knees).
18 Corrugated iron (steel) is galvanised and is commonly
used for roofing.
a Explain what will happen after all the zinc coating has
corroded away.
b Explain whether the zinc can be replaced.
19 If car bodies are galvanised, propose reasons why they
are also painted.
20 Identify problems associated with using plastic
shopping bags.
21 An optic fibre is transparent fibre that carries light
unbroken from one end to the other. Explain whether an optic fibre needs to be a monofilament.
22 Explain why natural fibres cannot drip-dry.
[Interpreting questions
]
23 Use a diagram to describe the bonding in metals that
allows:
a conduction of electricity b conduction of heat
24 Use the data in the table on page 34 to construct
the following graphs:
a a pie chart showing the amount of metals used each
year
b a bar graph showing when each metal is estimated to
run out
25 Construct a diagram showing what happens in the
electrolysis of copper chloride. Label the diagram and use chemical equations to show the chemical reactions at each electrode.
26 Aluminium metal is high on the activity series, yet is a
commonly used metal. Use Figure 2.3.5 to explain why it does not rust.
27 Phenylethene is an ethene molecule with one hydrogen
replaced by benzene, C6H6.
a Construct a diagram of a phenylethene molecule. b Polystyrene foam uses phenylethene as its monomer.
Construct a diagram showing ten phenylethene
monomers joined to form the polymer polystyrene. Worksheet 2.7 Materials crossword
Worksheet 2.8 Sci-words
a an alloy of copper b an alloy of iron c an impurity commonly
added to iron
d a commonly used pure
metal
e a non-metal abundant in
the Earth’s crust
f a scarce metal
g a metal that is cheaper to
recycle than to produce
h an ore i a native metal j a natural fibre k a synthetic fibre
made from wood products
l a monofilament fibre m a surfactant n an organic solvent
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By the end of this chapter you should be able to: use an analogy to describe voltage, current and
resistance
compare series and parallel circuits and describe everyday applications of each describe the relationship between voltage,
resistance and current, and use Ohm’s law to calculate values of each
contrast AC with DC electricity
describe how some electromagnetic devices operate
describe the main components needed for efficient transmission of electricity explain how waves transmit energy list and describe the different forms of
electromagnetic radiation
contrast analogue with digital signals and their use in communication
explain how communication signals can be transmitted
1 What do AM and FM on the radio dial stand for?
2 What are the voltage and frequency of the AC electricity that comes from our power points?
3 How do mobile phones find each other?
4 Describe an appliance that uses electromagnetism.
5 Who invented the telephone?
6 What is a digital message made up of?
Outcomes
5.3, 5.6.1, 5.6.3, 5.12