The document discusses the pH scale and importance of pH in various contexts. It begins by explaining the pH scale ranges from 0-14, with 7 being neutral. Solutions below 7 are acidic and above 7 are basic. It then discusses how pH is important biologically, as the human body and most living things can only survive within a narrow pH range. Other areas discussed where pH is important include agriculture, medicine, preventing milk and tooth spoilage, and some animals' and plants' self-defense mechanisms rely on releasing acidic substances.

1. BY : VEENU GUPTA
(PGT CHEMISTRY)
APS RAKHMUTHI

2. STRENGTH OF ACIDS AND BASES
The strength of acids or bases is
expressed on a scale known as
pH scale.

4. pH SCALE
A scale for measuring hydrogen ion
concentration in a solution, called pH
scale has been developed. The p in pH
stands for ‘potenz’ in German,
meaning power.
p= potential or Power
H = Hydrogen

7. pH =7 Neutral Solution
pH>7 Basic Solution
pH<7 Acidic Solution

8. pH range Nature of substance
0-2 Strongly acidic solution
2-4 Moderately acidic solution
4-6 Weak acidic solution
7 Neutral solution
7-10 Weak basic solution
10-12 Moderately basic solution
12-14 Strong basic solution

10. pH SENSITIVITY OF PLANTS AND
ANIMALS
 Human body works in a narrow range of pH 7
to 7.8. Acidity can be lethal for plants and
animals.
 pH of Digestive System: Stomach secretes HCl
to kill bacteria in the food. The inner lining of
stomach protects vital cells from this acidic
pH.

11.  • pH and tooth decay: Lower pH because of sour
food and sweet food can cause tooth decay. The pH
of mouth should always be more than 5.5.
• pH as self defense mechanism in plants &
animals: Certain animals like bee and plants like
nettle secrete highly acidic substance for self
defense.

12. IMPORTANCE OF pH IN EVERYDAY LIFE
 BIOLOGICAL IMPORTANCE
 AGRICULTURAL IMPORTANCE
 MEDICINAL IMPORTANCE
 IN PREVENTING SPOILAGE OF MILK IN DARIES
 PREVENTING TOOTH DECAY
 SELF DEFENCE BY ANIMALS AND PLANTS
THROUGH CHEMICAL WARFARE

13. BIOLOGICAL IMPORTANCE
 Biochemical reactions occurs at a definite pH
value our body works within a pH range of 7-7.8.
 Living organism can survive only in a narrow
range of pH change.
 Also when pH of rain water become less than
5.6,it is called as acid rain. when this acid flows
into rivers, it lowers the pH of river water and
therefore the survival of aquatic life in such rivers
become difficult

14. AGRICULTURAL IMPORTANCE
 Plants require a specific pH range for their healthy
growth.
 pH value of different type of soils is determined for
increasing agricultural production.
 Farmers usually add basic salts to neutralise the
effect of excess acids in soils and vice versa

15. MEDICINAL IMPORTANCE
 pH of urine and blood are determined for the diagnoses of various
diseases.
 Our stomach produces HCl which help in digestion of food. But if
during ingestion ,the stomach produces too much acid ,it causes
pain and irritation
 To relieve this pain antacids such as Magnesium hydroxide( milk of
magnesia) or aluminium hydroxide solution or ENO ,a mild base, is
used which brings the pH in stomach in normal range by
neutralising the acid in stomach
 Antacids are the chemical compounds which are used to neutalise
the effect of acids .They provide relief from the painful effects
arising due to acidity in stomach and maintain the pH of stomach.

16. PREVENTING SPOILAGE OF MILK IN DARIES
 In dairies ,pH of milk is adjusted to about 6.6.
 If pH of milk is less than 6.6 then taste of milk become sour.
 Milkman usually add Baking soda in milk to prevent the
change of its pH below 6.6 as baking soda is basic in nature
and thus neutralise the excess acid formed during the
curdling of milk.
 Milk having the addition of baking soda take more time to
convert into curd as firstly lactic acid neutralise the baking
soda present in milk and after that pH of milk decreases and
curdling process take place by lactobacillus bacteria present
in milk.

17. PREVENTING TOOTH DECAY
 Tooth decay starts when pH of mouth is lower than 5.5.this is
because the excess acid reacts with calcium phosphate of the
tooth enamel and causes its corossion.
 Bacteria present in the mouth produce acid by the
degradation of sugar and food particles remaining in mouth
after eating. Due to the production of acid, pH of mouth
become less than 5.5 and acid formed corrodes tooth enamel
 In order to prevent tooth decay ,clean mouth after eating
food and use basic tooth paste to neutralise the excess acids
present in mouth.

18. SELF DEFENCE BY ANIMALS AND PLANTS
THROUGH CHEMICAL WARFARE
 Bee sting and ant sting releases Formic acid which
causes pain and irritation.
 Use of mild base on the sting area gives relief by
neutralising acid.
 Similarly, stinging hair of leaves of neetle plant inject
formic acid causing burning pain which can be
neutralised by rubbing with the leaf of dock plant as its
leaves contain alkaline solution.

19. THANKS