The pH scale
Substance
pH number
Lemon juice
2
Oven cleaner
Colour with UI
Acid or alkali?
(Strong or weak)
Dark blue
Milk
Weak acid
Vinegar
Stronger acid
7
Tooth paste
Stomach acid
(hydrochloric acid)
Green
9
Red
Find the odd one out- why?
Acid or alkali
pH less than 7
Turns universal
indicator blue
Contains
H+
ions
HCl
Weak has a pH of
8-10
Feel soapy to
touch
Contains OH- ions
Nitric acid
Sulfuric acid
Sodium hydroxide
Strong has a pH of
1-3
H2SO4
Turns
universal
indicator
red
NaOH
pH more than
7
Makes a
salt when
added to a
metal
Often have
a sharp
bitter taste
May be an
irritant or
corrosive
1
What is universal indicator and what does it do?
2
Name a strong household acid and its pH
3
Name the 3 acids used in the science classroom
4
What do we call a reaction when we add an acid
to an alkali?
5
Give an everyday example of reaction (4)
6
What do all acids have in common?
7
How can we recognise an acid?
8
What does the hazard “irritant” mean?
9
What does the hazard “ corrosive” mean?
10
Reactions between acids and alkalis often give
out heat- what is the science name for this (hint
heat exits)
Reacting acids
Acid used
Metal salt name
Hydrochloric acid
Metal + Acid → metal salt + hydrogen
Magnesium + nitric acid →
Sulfuric acid
Nitric acid
Copper + hydrochloric acid →
Iron + sulfuric acid →
Copper oxide + hydrochloric acid →
Metal carbonate + Acid → metal salt + water + carbon dioxide
Copper carbonate + nitric acid →
Iron carbonate + hydrochloric acid →
Magnesium hydroxide + hydrochloric
acid →
Magnesium carbonate + sulfuric acid →
Metal oxide or hydroxide + Acid → metal salt + water
Lead oxide + sulfuric acid →
Reacting acids
Magnesium + sulfuric acid →
Zinc + hydrochloric acid →
Calcium carbonate + sulfuric acid →
Potassium hydroxide + hydrochloric acid →
Extension: can you write the BALANCED symbol equations
Writing ionic formula
If the charges are the same, they
cancel out directly
Example 1:
+
Magnesium
oxide
If the charges are the different, use the
crossover method- but remember the brackets
Example 1:
Example 2:
-
+
potassium
hydroxide
Example 2:
-
Iron oxide
Sodium sulfate
Name
1
Copper (II) sulfate
2
Magnesium sulfate
3
Lithium sulfate
4
Copper (II) nitrate
5
Calcium nitrate
6
Potassium sulfate
7
Copper (II) chloride
8
Zinc chloride
9
Sodium chloride
Positive ion
Negative ion
Chemical formula