How does a universal indicator work?

19 Fresh milk has a pH of 6. When it changes into curd (yogurt), will its pH value increase or decrease? Why? 20 (a) What is a universal indicator? For what purpose is it used? 20 Water is a neutral substance. What colour will you get when you add a few drops of universal indicator to a test-tube containing water? 21 Which chemical is injected into the skin of a person:

(a) during an ant's sting?

(b) duting the nettle leaf hair sting?

How can the effect of these stings be neutralized?