If you have 120. mL of a 0.100 M HEPES buffer at pH 7.55 and you add 4.00 mL of 1.00 M HCl, what will be the new pH? (The pKa of HEPES is 7.55.)

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.

60.0 - there are 3 significant numbers