Which of these is a example of a physical change

What is the strongest intermolecular force between an nacl unit and an h2o molecule together in a solution? covalent bonding dipole-dipole force hydrogen bonding ion-dipole force

How many liters of hydrogen gas will be produced at stp from the reaction of 7.179×10^23 atoms of magnesium with 54.219g of phosphoric acid (h3po4) the equation is 3mg + 2h3(> mg(po4)2+3h2

The number of neutrons is equal to the atomic number minus the atomic mass. a. true b. false