" Ortho and para hydrogen differ in "

Ortho and para hydrogen differn in

Ortho- and par - hydrogen differ in

Othro and para hydrogens differ in the

Ortho and para hydrogen have

Ortho and para hydrogen have :

Ortho-and para - hydrogens have

What do you mean by ortho and para hydrogen ? explain why the chemical properties of ortho and parahydrogen are the same but their physical properties are different.