A sample of seawater has a pH of 8. determine the new pH of the sample if the hydrogen ion concentration is increased by a factor of 100

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.

They can measure  the amount of energy gained or lost