What is the ph of a 0.001 62 m naoh solution?

The answer 
first of all, we should know that NaOH is a strong base. For such a product, the conentration of the OH -  is equivalent to the concentration of the NaOH itself.
that means:
[ OH -] = [ NaOH] =0.001 62 
and for a strong basis, pH can be calculated as pH = 14 + log [ OH -] 
first we compute log [ OH -] :
log [ OH -] = log (0.001 62)= -2.79

finally pH = 14 -2.79 = 11.20

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.