Pasteurisation of milk is
Neither physical nor a chemical change.
Well this is a tricky one! First of all, pasteurization of milk is quite an important process to make our milk safe to drink. In this process, milk is heated to a high temperature quickly and then quickly cooled down. This high temperature makes sure that all the bacteria in the milk are killed and the cooling ensures that the milk doesn't all get evaporated.
So, is there any change of state of the milk? Maybe a little, but we can ignore that. So there is no physical change.
Is there any new kind of milk we are getting. No. So there is no chemical change.
So pasteurisation of milk is neither a physical change nor a chemical change for the milk.