Question 1

Which of the following substances tastes sour?

Accepted Answer

Acids taste sour. Therefore, substances like lemon juice, vinegar, and tamarind, which contain acids, taste sour.

Question 2

What is the nature of substances that feel soapy to touch and taste bitter?

Accepted Answer

Bases are bitter in taste and feel soapy on touching. Examples include baking soda and soap.

Question 3

Which natural indicator is commonly used to test acids and bases, obtained from lichens?

Accepted Answer

Litmus is a natural indicator extracted from lichens. It turns red in acidic solutions and blue in basic solutions.

Question 4

What is the colour of blue litmus paper when dipped in a dilute hydrochloric acid solution?

Accepted Answer

Acids turn blue litmus red. Therefore, when blue litmus paper is dipped in hydrochloric acid, its colour changes to red.

Question 5

What colour does turmeric indicator turn when added to a basic solution like soap solution?

Accepted Answer

Turmeric is yellow in neutral and acidic solutions, but it turns bright red in basic solutions.

Acids, Bases and Salts — NCERT Class 7 Science Important Questions & Revision Notes