CLASS 7 ACIDS , BASES & SALTS
Properties of Acids
Properties of Bases
Have sour taste
Change blue litmus red
Acids are corrosive
Acids have replaceable hydrogen (H)
Have bitter taste
Change red litmus blue
Bases are corrosive
Bases have replaceable hydroxide ( OH)
Common Acids
in our daily life
INDICATORS
FA2  10 marks
( Table : TB page No. 50)
Substance which change colour in acidic medium and basic medium are called
indicators.
Types of Indicators
;- Two types Natural Indicators and Synthetic Indicators
Natural Indicators
Colour in Acid medium
Colour in Acid medium
1
2
3
Red
yellow
Dark pink
Blue
red
green
colorless
red
Pink
yellow
Litmus
Turmeric
China rose
SYNTHETIC indicators
1
2
Phenolphthalein
Methyl orange
LITMUS TEST FA2- (ACTIVITY)
SUBSTANCE
1
2
3
4
5
6
7
8
9
10
COLOUR OF RED
LITMUS
COLOUR OF BLUE
LITMUS
RESULT /
INFERENCE
Litmus  Litmus is a natural indicator. It is obtained from the Lichen which lives on the bark of the
tree. Litmus is available in two forms Litmus paper and Litmus solution.
Lichens Lichens are the symbiotic relationship between an alga and a fungus.
NEUTRAL SOLUTIONS The solutions which do not change the colour of either red
or blue litmus are known as neutral solutions. These substances are neither acidic nor
basic
Eg; Water, salt solution
ACIDS IN LABORATORY (FA2-5 marks)
NAME
FORMULA
SULPHURIC ACID
NITRIC ACID
HYDROCHLORIC ACID
PHOSPHORIC ACID
H2SO4
HNO3
HCl
H3PO4
BASES IN LABORATORY (FA2 – 5 marks)
NAME
FORMULA
SODIUM HYDROXIDE
POTASSIUM HYDROXIDE
CALCIUM HYDROXIDE
MAGNESIUM HAROXIDE
NaOH
KOH
Ca(OH) 2
Mg (OH) 2
S.No
1.
2
3
4
Test solution
TURMERIC INDICATOR TEST ( FA2 – 10 MARKS)
Colour
Orange juice
Lemon juice
Vinegar
Milk of magnesia
ACIDIC / BASIC
5
6
7
8
Baking soda
Lime water
Sugar
Common salt
CHINA ROSE INDICATOR TEST (FA2- 10 MARKS )
S.No
1
2
3
4
5
6
7
INITIAL COLOUR
TEST SOLUTION
FINAL COLOUR
Shampoo (dilute solution)
Lemon juice
. Soda water
. Sodium hydrogencarbonate
solution
. Vinegar
. Sugar solution
. Common salt solution
NEUTRALISATION
The reaction between an acid and a base to form Salt and water is called
Neutralisation . During this process heat is released.
Acid+Base  Salt+Water
(Heat is evolved)
Eg:
Hydrochloric acid + Sodium hydroxide  Sodium chloride + Water
HCl + NaOH NaCl + H2O
Eg;
Sulphuric Acid + Sodium hydroxide  Sodium sulphate + Water
H2SO4 + NaOH  Na2SO4 + H2O
NEUTRALISATION IN DAILY LIFE
1. Antacids and Indigestion
Stomach produces hydrochloric acid to help digestion. But too much of acid in the
stomach causes indigestion and pain.
. Antacids are mild bases used to relieve indigestion, It neutralises the effect of
excessive acid.
Eg: milk of magnesia, which contains magnesium hydroxide  Mg(OH)2
2. Ant bite
The sting of an ant contains formic acid. When an ant bites, it injects the formic acid into
the skin.
The effect of the sting can be neutralised by rubbing moist baking soda (sodium
hydrogen carbonate) or calamine solution, which contains zinc carbonate
3. Soil Treatment
Excessive use of chemical fertilizers makes the soil acidic. Plants do not grow well
when the soil is either too acidic or too basic.
If the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked
lime (calcium hydroxide).
If the soil is basic, organic matter is added to it. Organic matter releases acids which
neutralises the basic nature of the soil.
4. Factory Wastes
Factory wastes contain acids. If they are allowed to flow into the water bodies, the
acids will kill fish and other organisms.
Therefore the factory wastes are,neutralised by adding basic substances.