The acids are sour in taste and change the colour of blue litmus to red, whereas, bases are bitter and change the colour of the red litmus to blue. Litmus is a natural indicator, turmeric is another such indicator. A stain of curry on a white cloth becomes reddish-brown when soap, which is basic in nature, is scrubbed. It turns yellow again when the cloth is washed with plenty of water.
1. When the litmus solution is neither acidic nor basic, its colour is ______
(i) Blue
(ii) Red
(iii) Purple
(iv) None of these
2. There are many other natural materials which indicate the presence of acid or base in a solution. These are called _____
(i) Signals
(ii) Indicators
(iii) Both A and B
(iv) None of these
3. Synthetic indicators such as _______ are used to test for acids and bases.
(i) Methyl orange
(ii) Phenolphthalein
(iii) Both A and B
(iv) None of these
4. Natural indicator is
(i) Methyl orange
(ii) Turmeric
(iii) Aloe vera
(iv) None of these
5. Soap changes red litmus blue. Yes or No?
(i) YES
(ii) NO
