Spec. 5.4.2.4
NEUTRALISATION AND THE PH SCALE
DO NOW – Connect Task (Green pens please)
Pink 0-3 marks
Yellow 4-6 marks
• List the equipment
• State the test used to
required to produce a
identify carbon dioxide
sample of a pure dry salt
gas
• Organise the following
• Write a method for the
into a method
practical as a flow chart
-Leave to crystallise for
• Create a risk
24hours in a cool place
assessment for this
-Gently heat 10cm3 of acid
practical.
-Filter the solution
- Add a spatula of copper
oxide and stir, keep adding
till in excess
- Gently heat the filtrate
till half the solution has
evaporated
Green 7-8 marks
• Write a method that
would produce a pure
dry sample of Magnesium
sulfate from magnesium
oxide and sulfuric acid.
Include the equipment
needed and a brief risk
assessment
PROGRESS INDICATORS
Good progress
Outstanding progress
Grade 1-3
Use the pH scale to identify
acidic or alkaline solutions.
Define the following terms:
acid, base, alkali, neutral.
Describe the use of
universal indicator or a wide
range indicator to measure
the approximate pH of a
solution.
Grade 4-6
Recall the ionic equation for
a neutralisation reaction.
Interpret the ionic equation
for a neutralisation reaction.
WORD CONSCIOUSNESS
pH Scale – A scale used to show how acidic/basic a
substance is.
Neutral - a substance that is not acidic or alkaline e.g.
water
Neutralisation - a reaction where an acid is reacted
with an alkali to produce a salt and water. The products
are neutral.
PH SCALE
Key Facts
• Ranges from pH 0-14. Any pH below 7 is an acid, any pH above 7 is an
alkali. pH 7 is neutral.
• The colours shown above are seen when using universal indicator.
• H+ ions make a substance an acid. OH- ions make a substance an alkali.
ACTIVITY 1 - DEFINE THE FOLLOWING
TERMS: ACID, BASE, ALKALI, NEUTRAL
Match the key term to its definition.
acid
base
A substance that forms an aqueous solution with a
pH of less than 7
A base that dissolves in water to form a solution
greater than 7
alkali
neutral
Any substance that will react with an acid to form
a salt
The product when an acid neutralises a base
Add these to your word consciousness in your books please
ACTIVITY 2 - USE THE PH SCALE TO
IDENTIFY ACIDIC OR ALKALINE SOLUTIONS.
Substance
Colour with
universal indictor
pH
Acid / alkali / neutral
Pure water
Vinegar
Bleach
Soap
Stomach acid
Washing up liquid
Normal rain
Acid rain
Pancreatic juices
Caustic soda (drain cleaner)
CHALLENGE: Can you distinguish between strong and weak acids and alkalis, if so add it
to the last column, e.g. strong acid
ACTIVITY 2 ANSWERS
Substance
Colour with
universal indictor
pH
acid / alkali / neutral
Pure water
7
neutral
Vinegar
3
(weak) acid
Bleach
12
(strong) alkali
Soap
11
(weak) alkali
Stomach acid
1
(strong) acid
Washing up liquid
9
(weak) alkali
Normal rain
5
(weak) acid
Acid rain
4
(weak) acid
Pancreatic juices
10
(weak) alkali
Caustic soda (drain cleaner)
14
(strong) alkali
SA
In red pens please
ACTIVITY 3 -DESCRIBE THE USE OF UNIVERSAL
INDIC ATOR OR A WIDE RANGE INDIC ATOR TO
MEASURE THE APPROXIMATE PH OF A SOLUTION.
QUESTIONS
1. Universal indicator is a wide range indicator. What is meant by
the term ‘wide range indicator’?
2. Give one advantage of using a wide range indicator.
3. Give one advantage of using a pH probe attached to a pH meter.
ACTIVITY 3 ANSWERS
QUESTIONS
1. Universal indicator is a wide range indicator. What is meant by
the term ‘wide range indicator’?
A dye that gradually changes colour over a broad range of
pH
2. Give one advantage of using a wide range indicator.
Useful for estimating pH of a solution
3. Give one advantage of using a pH probe attached to a pH meter.
It is more accurate than an indicator
SA
In red pens please
ACTIVITY 4 -RECALL THE IONIC EQUATION
FOR A NEUTRALISATION REACTION
Fill in the gaps.
hydrogen ions (H+) in aqueous
Acids produce h_________
solutions.
hydroxide ions
Aqueous solutions of alkalis contain h__________
(OH-).
In neutralisation reactions between an acid and an alkali,
hydrogen ions react with hydroxide ions to produce
w________.
water
Using the coloured cards in your
planner show red for false, green for
true
An acid is anything with a pH below 7
An alkali is anything with a pH of 7 or above
A substance is acidic due to the H+ ions
Neutralisation produces a salt and hydrogen
An substance is an alkali because of the OHions
pH 2 is an alkaline substance