Q1. Fill in the blanks.
i. Change of colour in an acid and a base depends on the type of the_____________.
ii. Acid turns ___________litmus red.
iii. Bases turn __________litmus blue.
iv. Litmus has a _________________colour in distilled water.
v. In neutralisation reaction a new substance is formed. This is called________.
vi. Lemon juice is ____________in nature.
i. Nitric acid turns red litmus blue. _________
ii. Sodium hydroxide turns blue litmus red. _________
iii. Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. ________
iv. Indicator is a substance which shows different colours in acidic and basic solutions. ________
v. Tooth decay is caused by the presence of a base. ________
vi. If an indicator changes colour with a base, it does not change colour with an acid. _________
Q3. What is acid rain?
Q4. Which acid naturally present in our stomach?
Q5. What is the role of hydrochloric acid in the stomach?
Q6. Which acid is present in an ant sting?
Q7. What is the nature of soap solution?
Q8. What is the nature of distilled water?
Q9. State the nature of baking soda.
Q10. Where does the word acid come from?
Q11. Why curd, lemon juice, orange juice and vinegar taste sour?
Q12. Which is the most commonly used natural indicator?
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.
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?
Q17. What does organic matter do in soil?
Q18. Why solid baking soda does not change colour of dry litmus paper?
Q19. How acidic soil can be treated?
Q20. What are salts? Give example.
Q21. What is the role of DNA in the cell of the human body?