Chapter 4 discusses acids, bases, and neutral substances, defining acids as sour-tasting chemicals and bases as bitter and soapy. It explains the use of indicators like litmus, turmeric, red cabbage, and phenolphthalein for testing acidity and alkalinity, and explores the environmental impact of acid rain. The chapter also covers neutralization reactions between acids and bases, highlighting their applications in everyday life, such as in treating indigestion and soil balance.

1. CHAPTER - 4
ACIDS, BASES & SALTS

3. • An acid is a chemical substance
that has a sour taste.
• The word acid comes from the
Latin word acere – means sour
• Many food items such as
lemons, curd, vinegar and
orange taste sour because of the
presence of acid in them.
• Acidic Substances are the
substances that contain acid in
them.
ACIDS

4. EXAMPLES OF ACIDS
• Lemon juice
• Orange juice
• Vinegar
• Curd
• Tamarind
• Amla
• Unripe Mango
• Grapes

9. BASE
(ALKALINE)
Base bitter to taste
Soapy to touch
Bases are found in different
substances such as bleach, ammonia,
washing powder and soap.

10. EXAMPLES
OF BASE
DETERGENT BAKING SODA DRAIN CLEANER
ANTACID
BASE
AMMONIA
SOPS(HAND, DISH)
LIME WATER

11. NAME OF
BASE
- FOUND IN
Sodium hydroxide/ Potassium hydroxide - Soaps
Calcium hydroxide - Lime Water
Ammonium hydroxide - Window
cleaners
Magnesium hydroxide - Milk of magnesia

13. NEUTRAL SUBSTANCE
Neutral Substance is any
substance which is neither acidic
nor basic in nature. Examples are
pure water, table salt, sugar
solution etc.

15. INDICATORS
•We cannot taste every object
and find its nature.
•Special type of substances used
to test whether a substance is
acidic or basic -indicators.
•The indicators indicate the
presence of an acid or base in a
substance by changing their
colour.

16. EXAMPLES
OF
INDICATOR
Litmus (paper/solution)
Turmeric
China rose
Phenolphthalein Indicator

17. NATURAL
INDICATO
R
(LITMUS)
Litmus: A natural indicator
It is extracted from lichens. It has a mauve
(purple) colour in distilled water.
When added to an acidic solution, it turns red
and when added to basic solution it turns
blue.
It is available in the form of a solution or in
the form of strips of paper.
Generally, it is available as red and blue
litmus paper.

20. ACTIVITIES

21. LITMUS
PAPER

22. Can we expect the same
result using solid baking
soda and dry litmus paper??

23. Neutral Solutions
The solutions which do not
change the colour of
either red or blue litmus
are known as neutral
solutions

24. TURMERIC
(NATURAL
INDICATOR
)
• To use turmeric as an indicator it is generally mixed with
water to form a paste which is then put on blotting paper
and dried to form thin strips of turmeric paper.
• The turmeric paper is then put into the solutions in order
to determine their acidic or basic nature.

25. Turmeric is a natural
indicator
which changes
colour from yellow to
red-orange when
added to a basic
solution.
It stays yellow in
acidic solution.

26. Prepare a greeting card
using turmeric and a base

27. TURMERIC (NATURAL
INDICATOR)

28. Turmeric stain on
white shirt turns red
when it is washed with
soap

29. CHINA ROSE
China Rose petals are kept in warm water and a coloured solution is
obtained. This coloured solution is used as an indicator to identify the
acidic or basic nature of substances.
Acidic solution turns dark
pink (magenta)
Basic solution turns green

31. Natural indicators

32. Red cabbage is another acid-base indicator
Red cabbage changes color in acid, base, and neutral solutions as
follows:
Acidic: Red cabbage turns red or pink in acidic solutions
Basic: Red cabbage turns green or yellow in basic solutions
Neutral: Red cabbage remains purple or blue in neutral solutions

35. Acid Rain
• The rainwater containing a higher level of acid
than normal is called acid rain.
• The rainwater becomes acidic when gases like
sulphur dioxide, nitrogen dioxide and carbon
dioxide are released into the air as pollutants
during the burning of various types of fuels.
• These gases then dissolve in rain drops to form
sulphuric acid, nitric acid and carbonic acid
respectively and makes rain water acidic.

36. Impact of Acid Rain on the Environment
• Acid rain eats up the leaves of the trees which then gradually
die. By losing leaves, the trees die.
• Acid rain also damages crop plants in the fields

37. Impact of Acid Rain on the Environment
• Acid rain makes the water of lakes, ponds and rivers too acidic
due to which fish and other aquatic animals get killed.

38. Impact of Acid Rain on the Environment
• Acid rain damages the metal
structures like steel bridges and
the surfaces of buildings and
monuments made of stone.
• This damage can be noticed by
the change in the colour of
these buildings/structures.

39. PHENOLPHTHALEIN
INDICATOR
• Phenolphthalein is a synthetic
indicator which is colourless in
acidic solution but turns pink to
bright pink ( in strong bases) as the
solution becomes alkaline(basic).
• Phenolphthalein is colourless in
nature

41. What happens when an acid is mixed with a
base?
Video

42. NEUTRALISATION
When an acidic solution is mixed
with a basic solution, both the
solutions neutralise the effect of
each other.
the reaction between an acid and a
base is known as neutralisation.
Salt and water are produced in
this process with the evolution of
heat.

43. • When an acid and a base are mixed, they react to form water and
a salt.
• This reaction is called an acid-base reaction or a neutralization
reaction.
• In neutralization reaction heat is always produced or evolved. And
this raises the temperature of the reaction mixture.
• The salt formed may be acidic, basic or neutral in nature.
• This depends upon the relative strength of acids and bas used in
the reaction.

44. • Salt has two parents: an acid and a base.
• Therefore, the name of a salt consists of two parts.
• The first part of the salt's name is derived from the name of the
base and the second part of the salt's name is derived from the
name of the acid.
• Hence, the name of the salt 'sodium chloride' comes from
'sodium hydroxide' and 'hydrochloric acid'.

47. Boojo added dilute sulphuric acid to lime water.
Will the reaction mixture become hot or cool ?

51. NEUTRALIZATION IN EVERYDAY
LIFE
1. Indigestion -
During indigestion, taking milk of magnesia (magnesium hydroxide)
gives us relief as it neutralizes the effect of excess acid produced inside
the stomach.

52. 2. Ant Bite -
The effect of ant sting which is caused by formic acid can be neutralized by
rubbing moist baking soda (basic in nature).
3. Soil Treatment -
Plants do not grow well when the soil is either too acidic or too
basic. When 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.

53. 4. Factory wastes -
The wastes of many factories contain acids. If they are allowed to flow in to
the water bodies, the acids will kill fish and other organisms. The factory
wastes are, thererfore, neutralised by adding basic substances.

54. Thank you