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Doc Brown's Chemistry
KS3 SCIENCE-Chemistry QCA Unit 7E Acids and alkalis
KS3 Quizzes or task sheets based on this 7E summary: four word-fill worksheets * multiple choice quiz * X-word
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 QCA 7E "Acids and
alkalis" Multiple Choice Questions
for Science revision on common acids/alkalis - pH scale,
indicators, neutralisation reaction, uses etc.
 7Ewf1-4
four handy linked word-fill worksheets * 7Ewf2 *
7Ewf3 * 7Ewf4 *
The BIG hard
on-line crossword puzzle 
(with letter hints),
printout of the BIG version
OR the smaller
EASIER
(with letter hints), printout
of the smaller EASIER version
matching pair quiz
on pH (drag & drop version or printout)
and
on hazard symbols (drag & drop
version or printout)
The
7E crossword and word-fill
* KS3 Science multiple Choice Quizzes for
chemistry, worksheets and practice chemistry questions for pupils revising Key
Stage 3 science tests revision help for secondary students *
In the unit you should learn how to ...
- classify acids and alkalis as chemicals with distinct
properties and uses.
- use indicators to classify solutions as acidic, alkaline or neutral.
- use the pH scale to compare the acidity and alkalinity of different
solutions.
- begin to explore neutralisation i.e. the
reaction between an acid and an alkali.
- interpret observations, making comparisons and seeing simple patterns.
- investigate fairly the effectiveness of different antacids
i.e. compare their ability to neutralise acids
- recognise and deal
with risks and hazards relating to acids and alkalis.
- name some common acids and alkalis.
- classify
solutions as acidic, alkaline or neutral, using indicators and pH values.
- describe what happens to the pH of a solution when it is
neutralised
- describe
some everyday uses of acids, alkalis and neutralisation
Its handy if you ...
- know that soluble solids dissolve and form solutions,
substances that don't dissolve are insoluble
- have had experience of mixing materials and seeing that new materials are
formed as a result of a reaction between them
- understand the difference between a
reversible and irreversible change (physical or chemical)
Some important words for you to understand, use
and spell correctly
- names of laboratory acids and alkalis, eg hydrochloric acid,
sodium hydroxide
- names of classes of chemical, eg acid, alkali,
salts
- words with different meanings in scientific and everyday contexts, eg
indicator, solution, neutral, react, equation, weakly, strongly
- words with similar but distinct meanings, eg harmful, corrosive,
caustic, sour, irritant
- words and phrases relating to scientific enquiry, eg hazard, risk, pH
range, evaluate, strength of evidence, alkaline, acidic, neutral, indicator, universal indicator, colour
change, dilute, ?
What are acids and alkalis like and where do we use them?
- many household materials are acids and are not hazardous
eg lemon juice or vinegar
- identify some everyday uses of acids, eg
fruit juices or vinegar in foods, medicines like aspirin, using acids to
clean materials like metal plates, oven cleaners can be strongly alkaline
- recognise and interpret common hazard signs for harmful, irritant and corrosive
substances
- how to deal with acids or alkalis if they are spilt/splashed
on the skin eg dilute/wash with lots of water
- adding water to an acid or alkali solution dilutes it and
makes it less hazardous
- describe how to work safely with acids and alkalis and what to do
if a spill occurs, e.g. wear safety goggles, dilute split acids/alkalis
- acids are distinguished from alkalis using
indicators such as litmus or universal indicator
- (both turn red in acid (pH <3)
or blue in alkali (pH > 9), but universal has lots of colours to get
a more accurate estimate of the pH including green for neutral pH7 and
how strongly acid from pH 6 to 1 and how strongly alkaline from 8 to 1
etc.4)
- common names, eg caustic soda (sodium
hydroxide), bicarbonate of soda (sodium hydrogencarbonate), may be used where appropriate.
- Adding water to concentrated sulphuric acid is hazardous because
the reaction is highly exothermic, so concentrated sulphuric acid should be
diluted by adding a small amount of the concentrated acid to a lot of water.
- know that sulfur is the internationally
accepted spelling and sulphuric acid can be called sulfuric acid
How can acids and alkalis be identified and distinguished from each
other?
- how to extract the dyes from plant materials
and that acids and alkalis can change the colours of some of these natural dyes and
that this can be used to classify them eg from red cabbage, raw beetroot, blackcurrant, litmus,
- to test and classify solutions as acidic,
neutral or alkaline, using indicators
- compare the results with different dyes and
establish that there are two classes of solution
and that the dyes can indicate which is which
- recognise that solutions of dyes which show one
'indicator' colour in acids
and another in alkalis are called indicators
- recall the names of some common laboratory acids
eg hydrochloric acid, sulphuric acid, sodium hydroxide, and alkalis e.g.
sodium hydroxide, calcium hydroxide
Is there a range of acidity and alkalinity?
- universal indicator gives a range of colours in acidic and
alkaline solutions (typically from pH 0-14)
- that pH numbers indicate how acidic or alkaline a solution is
- that neutral solutions are pH 7, acidic solutions
are below pH 7 and
alkaline solutions are above pH 7
- the pH of a solution can be got from an appropriate colour
chart eg when using universal indicator
- classify the solution as strongly/weakly, acidic/alkaline,
or neutral
- relate their classification to the use of the acid or alkali and
associated hazards
- At this stage, pH can be used to describe strongly or weakly
acidic or alkaline solutions.
- predict the effect on pH of
making an acid more dilute or more concentrated and how this would
affect its corrosiveness. When diluted, acids still give a pH <7, but
when diluted the pH will rise since the solution would be less strongly
acidic.
What happens when an acid is added to an alkali?
- the uses of acids and alkalis in
a range of everyday situations, eg
hair and skin care, treatment of
stings and bites,
treatment of
indigestion, food preservation,
treatment
of soil.
- how living things use acids, eg
ants, nettles, humans in digestion.
- identify and note key points about the range of pH
used and potential harmful effects,
- that a neutral solution can be obtained by adding an acid to an
alkali in the right proportions
- the changes in pH when a solution of
an acid is added drop by drop to a solution of an alkali
- describe that when an acid is added to an alkali, the pH of the
mixture falls as it become neutralised
- describe that when an alkali is added to an
acid, the pH of the
mixture increases as it become neutralised
- explain how to obtain a neutral solution of
about pH7 by
mixing an acid and an alkali
- describe with a graph the way pH changes as more alkali
is added
- investigate changes in
temperature during neutralisation and be introduced to the idea that a
chemical reaction is taking place
- neutralisation is exothermic, which
means heat is given out, so the temperature rises.
Where is neutralisation important?
- the alkali lime is used to treat soil that is
too acid for healthy plant growth
- acid bee stings can be treated with a weak
alkali like bicarbonate of soda or calomine (zinc oxide paste)
- and alkaline wasp stings can be treated with a weak acid
like vinegar
- too much stomach acid! - common antacid
indigestion remedies - how are the remedies are
intended to work? what sort of solution would work and be
safe to take?
- antacids are mild alkalis including
bicarbonate of soda (alka-selza) and magnesium hydroxide ('milk of
magnesia')
- suggest ways in which one remedy might be more
effective than others
- investigating the effectiveness of antacids:
- does one
tablet of each antacid neutralise the same amount of acid?
- do the
antacids neutralise acid equally quickly?
- how can you follow the neutralisation?
e.g. by adding universal
indicator and following the colour change
- how can you measure how much acid
is neutralised by a particular mass of 'antacid' powder?
- is the
reaction is fast or slow to the neutralisation point?
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