Acids are sour substances that turn litmus paper red, while bases are bitter substances that turn litmus paper blue. Examples of common acids include citric acid found in citrus fruits and hydrochloric acid. Common bases include sodium hydroxide found in soap and calcium hydroxide in limewater. Indicators like litmus paper, china rose, and turmeric can test whether a substance is acidic or basic by changing color in their presence. The reaction between an acid and base is called neutralization, which produces salt and water with the evolution of heat. Neutralization can be used to treat insect stings, indigestion, soil acidity, and neutralize acidic factory waste.

2. ACIDS
 Acids are those substances which are sour in taste,
produce burning sensation on touching and which turn
blue litmus to red. Examples – Citric acid, oxalic acid,
hydrochloric acid.
 Curd, lemon juice, orange juice and vinegar taste
sour. These substances taste sour because they
contain acids.
 The chemical nature of such substances is a acidic. The
word acid comes from the Latin word acere which
means sour.

3. ACIDS

4. NAME OF ACID FOUND IN
Acetic Acid Vinegar
Formic acid Ant’s sting
Citric Acid Citrus foods such as
oranges, lemons etc
Lactic Acid Curd
Oxalic Acid Spinach
Ascorbic Acid (Vit ‘C’) Amla, citrus fuits
Tartaric Acid Tamarid, grapes, unripe
mango etc

5.  Bases are those substances which are bitter in taste,
are soapy to touch and which turn red litmus to blue.
Example Sodium Hydroxide, Potassium hydroxide etc.
 The nature of such substances is said to be basic.
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6. NAME OF BASES FOUND IN
Calcium Hydroxide Lime Water
Ammonium Hydroxide Window Cleaner
Sodium
Hydroxide/Potassium
Hydroxide
Soap
Magnesium Hydroxide Milk of Magnesia

7.  The special substances which are used to test whether a
substance is acidic or basic are known as indicators
 The indicators change color when added to a solution
containing an acidic or a basic substance.
 Some of the naturally occurring indicators are turmeric,
litmus, china rose petals etc.
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8. 8
LITMUS PAPER

9. Acids
 turns blue litmus red
 taste sour
 Acids corrode metals
Bases
 turns red litmus blue
 taste bitter
 Feel Slipper
 Most hand soaps and drain cleaners are bases

10. TEST SOLUTION CHINA ROSE
INDICATOR
TURMERIC
INDICATOR
LITMUS SOLUTION
BLUE/RED
HCL (Hydrochloric
Acid)
Red No change Blue to Red
NAoH
Sodium Hydroxide
Green Red Red to Blue
Soap solution Green Red Red to Blue
Baking Powder Green Red Red to Blue
Lemon Juice/
Tomato Juice
Red No Change Blue to Red
Vinegar Red No Change Blue to Red
Sugar No Change No Change No Change

11.  The reaction between an acid and a base is known as
neutralization. Salt and water are produced in this
process with the evolution of heat.
 In neutralization reaction heat is always produced or
evolved.
 In neutralization reaction a new substance is formed.
This is called salt. Salt may be acidic, basic or neutral in
nature.

12. Insect Stings
Bee stings are acidic and can
be neutralized with baking soda.
Wasp Stings are alkaline and can
be neutralized with Vinegar.
Indigestion
Our Stomach carriers around
hydrochloric acid. Too much of
this leads to indigestion. To cure
indigestion, you can neutralize
the excess acid with Milk of
Magnesia or take antacid

13. Soil Treatment
When soils are too acidic they can
be treated with slaked lime, chalk or
quicklime, all alkalis. Plants and
Crops grow best in neutral soils.
Factory waste
Liquid waste from factories is often
acidic. If it reaches a river it will
destroy and kill sea life of many
forms. Neutralizing the waste slaked
lime can prevent this.