Question

Heating zinc oxide is a physical change. How?

. What is the colour of phenolphthalein acidic and basic media?

Answer 1

1) When Zinc Oxide is heated, it turns a pale, lemony color and when take off the heat, turns back to white. Nothing has happened to the zinc, it has not thermally decomposed.
so it's a physical change.

2)

​​​​Phenolpthalein is colourless in the acidic medium and neutral medium ( at pH 1 to 7)

And in basic or alkaline medium it changes to pink colour ( it shows pink colour at basic pH - 10)