Why is the melting of ice a physical change

A.It changes the chemical composition of water.
B. It does not change the chemical composition of water.
C. It creates new chemical bonds.
D. It forms new products.
E. It is an irreversible change that forms new products.

B

There is so much confusion on the chemical change vs physical change issue, that it should NEVER be included in beginning chemistry. It usually finds its way into the first chapters of HS and freshman chemistry texts, and the students don't know enough chemistry to really be able to make sense of it.

In one sense a phase change is "physical" because it doesn't produce a new chemical. But, at the atomic scale phase changes are chemical changes because they involve the making or breaking of intermolecular chemical bonds.

Ice is held together by strong hydrogen bonds. Hydrogen bonding is a weakly covalent intermolecular bond that forms between the hydrogen atoms of one molecule and the oxygen of an adjacent molecule. Ice has a rigid hexagonal crystalline structure because of hydrogen bonding. When ice melts, these bonds must be broken and that takes a fair amount of energy. Bond breaking is an example of a chemical process, therefore, the melting of ice is a chemical change.

By the way, the reversibility issue is nonsense. Some physical changes are reversible and some are not. Some chemical changes are reversible and some are not. The only thing that a discussion of "reversibility" shows is the ignorance of the person making the argument one way or the other.

A physical change is a change that occurs without a change in identity of the substance. Since melting of ice does not produce any change in chemical identity, melting is therefore a physical change.

B is the answer.

( B )