Help me out real quick please

Work = force × a. work b. energy c. distance d. momentum

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.