The answer is: It stays the same
In a physical change, there is only a change in the form of the objects, but the chemical composition of the oject remained the same. Since mass is affected by this compisition, the mass of an object that undergone a physical change would remain the same.
For example, when you turn 1kg of water into ice (physical change), the mass of the ice will remain the same. The only way for you to change this is by conducting a chemcial change such as mixing the water with other substances.