Bases and Salts
Q1. Fill in the blanks.
Change of colour in an acid and a base
depends on the type of the indicator.
Acid turns blue litmus red.
Bases turn red litmus blue.
Litmus has a mauve (purple) colour
in distilled water.
In neutralisation reaction a new substance
is formed. This is called salt.
Lemon juice is acidic in nature.
Nitric acid turns red litmus blue. False
Sodium hydroxide turns blue litmus red. False
Sodium hydroxide and hydrochloric acid
neutralise each other and form salt and water. True
Indicator is a substance which shows
different colours in acidic and basic solutions. True
Tooth decay is caused by the presence of a
If an indicator changes colour with a base,
it does not change colour with an acid. False
Q3. What is acid rain?
rain containing excess of acids is called an acid rain.
Q4. Which acid naturally present in our stomach?
Q5. What is the role of hydrochloric acid in the stomach?
Hydrochloric acid (HCl) helps us to digest food.
Q6. Which acid is present in an ant sting?
Formic acid is present in an ant sting.
Q7. What is the nature of soap solution?
solution is basic in nature.
Q8. What is the nature of distilled water?
Distilled water is neutral.
Q9. State the nature of baking soda.
soda is basic in nature.
Q10. Where does the word acid come from?
word acid comes from the Latin word acere which means sour.
Q11. Why curd, lemon juice, orange juice and vinegar taste sour?
substances taste sour because they contain acids.
Q12. Which is the most commonly used natural indicator?
The most commonly used natural indicator is litmus.
Q13. Tom rubs a solution between fingers and feels soapy, what
is the nature of that solution?
Q14. Name the acid which is present in each cell of our body.
cell in our body contains an acid, the deoxyribonucleic acid or
Q15. When red litmus paper is dipped in a solution; it remains
red, what is the nature of the solution?
Q16. What are the effects of acid rain?
rain can cause damage to buildings, historical monuments, plants and animals.
Q17. What does organic matter do in soil?
the soil is basic, organic matter is added to it. Organic matter releases acids
which neutralises the basic nature of the soil.
Q18. Why solid baking soda does not change colour of dry litmus
solid baking soda does not change colour of dry litmus paper because in solid
states ions are not free to move.
Q19. How acidic soil can be treated?
the soil is too acidic, it is treated with bases like quick lime (calcium
oxide) or slaked lime (calcium hydroxide).
Q20. What are salts? Give example.
neutralisation reaction a new substance is formed. This is called salt. Salt
may be acidic, basic or neutral in nature. Example: Sodium chloride.
Q21. What is the role of DNA in the cell the human body?
controls every feature of the body such as our looks, colour of our eyes, our