The document covers the classification and properties of acids, bases, and indicators, emphasizing their everyday applications and neutralization reactions. It describes various examples of acids and bases, as well as natural and synthetic indicators used to test pH levels. Learning outcomes include understanding these substances' characteristics and performing relevant tests in practical scenarios.

1. Class 7 Science
ACIDS,
BASES & SALTS

2. Observe the following situations carefully:

3. Which of the following would you suggest as a remedy for the following situations–
lemon juice/lemon, vinegar or baking soda solution?
How do you classify these substance ?

4. Learning Outcomes:
•To know about some common acids, bases and
indicators
•To understand the properties of an acid.
•To apply knowledge and find out some commonly
available natural and synthetic indicators from our
surroundings.
•To analyse what is neutralization reaction.
•To evaluate some common neutralization reactions in
our everyday life.
•To perform tests and find out the nature of various
substances available around us.
NOTEBOOK WORK

5. NOTEBOOK WORK

6. • Acids are substances that taste sour and are corrosive in nature.
• These substances are chemically acidic in nature.
• For example: Orange juice, curd, vinegar, hydrochloric acid ,sulphuric acid and
nitric acid.
Acids

7. NOTEBOOK WORK

8. Vinegar, a diluted solution of acetic acid, has
various household applications. It is primarily
used as a food preservative.
Sulfuric acid is widely used in batteries.
The batteries used to start the engines of
automobiles commonly contain this acid.
Examples of Acids

9. • Bases are substances that, in aqueous solution, are slippery to the touch and
bitter in taste.
• These substances are chemically basic in nature.
• For example- soap, baking soda,ammonium hydroxide, calcium hydroxide.
Bases

10. NOTEBOOK WORK

11. The manufacturing of soap and paper involves
the use of sodium hydroxide.
As a foaming agent in fire extinguishers –
Aluminium hydroxide
Examples of Bases

12. Observe these Materials

13. • Substances, which are used to test whether a substance is acidic or basic are
called indicators.
• In Plants or plant parts contain useful chemicals that are used for testing an
acidic or basic property of a solution are termed as natural indicators.
Indicators
NOTEBOOK WORK
(first point only)

14. China rose
NOTEBOOK WORK
(blank side)

15. • Litmus is the most commonly used natural indicator which is extracted from lichens.
• It has a mauve color in distilled water.
Litmus : A Natural Indicator

16. • Litmus solution is a purple dye, which is extracted from lichen, a plant
belonging to the division Thallophyta, and is commonly used as an
indicator.When the litmus solution is neither acidic nor basic, its colour is
purple. These are called acid-base indicators .
Litmus : A Natural Indicator

17. Litmus : A Natural Indicator
• It turns red when added to an acidic solution & turns blue when added to a basic
solution.
Note the colour change in
your notebook

18. Questions
1. State differences between acids and bases.
2. Ammonia is found in many household products, such as window cleaners. It
turns red litmus blue. What is its nature?
3. Name the source from which litmus solution is obtained. What is the use of this
solution?
4. Is the distilled water acidic/basic/neutral? How would you verify it?
NOTEBOOK WORK

19. Assertion and Reason
Q1. Assertion (A): Lemon juice turns blue litmus paper red.
Reason (R): Lemon juice contains citric acid, which is a weak base.
Q2. Assertion (A): A base feels soapy to touch.
Reason (R): Bases react with oils on the skin to form soap-like substances.
.
Both (A) and (R) are true, and (R) is the correct explanation of (A).
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is true, but (R) is false.
(A) is false, but (R) is true.
NOTEBOOK WORK

20. Let’s test acidic/basic substances using tumeric
paper
NOTEBOOK WORK

21. China rose indicator changes to magenta when brought in contact with acids
and it changes to green when brought into contact with bases.
Note the colour change in your
notebook

22. Red Cabbage : A Natural Indicator
The juice of red cabbage is originally purple in colour. Juice of red cabbage turns reddish
with acid and turns greenish with base.

23. What is the name of solely sensory nerve and conveys the
sense of smell? Olfactory Nerve

25. • Substances which change their smell when mixed with acid or base are
known as Olfactory Indicators.
• The olfactory indicators have a characteristics odour.
Olfactory Indicators

26. • These type of indicators are used in laboratories to check whether a given
solution is a basic or an acidic solution by a process known as olfactory
titration.
• This odour in olfactory indicators is changed in acidic or basic solution
and helps us in detecting whether a given sample solutions is acidic or
basic in nature.
Olfactory Indicators

27. Vanilla:Olfactory Indicator

28. The smell of vanilla vanishes with base, but its smell does not vanish with an
acid.
Vanilla:Olfactory Indicator

29. Synthetic Indicators
• Indicators that are synthesized in the laboratory are known as Synthetic
Indicators. For example; Phenolphthalein, methyl orange.
Note the colour change
in your notebook

30. Synthetic Indicators
Methyl orange is originally orange in colour. It turns into the red with acid and turns into
yellow with base.
Note the colour change in
your notebook