give two examples to show that when substances are mixed ,it may result in a chemical or a physical change depending on the conditions
When salt is mixed with water, a salt solution is obtained but no new compound is formed and salt can be separated from water easily. So, it is a physical change.
When a small quantity of curd is added to warm milk, stirred and left for few hours the entire milk changes into curd. This process cannot be reversed and thus is a chemical change.