Question

consider the following transformations. which of the statement best describes the process

Before After A) A chemical change occurs in which atoms rearrange to form a new compound. B) A chemical change occurs in which an ionic compound is formed from diatomic elemen C) A chemical change occurs in which no atoms rearrange to form a new substance. D) A physical change occurs in which no atoms rearrange to form a new substance. E) A physical change occurs in which atoms rearrange to form a new compound.

Answer 1

(D) A physical change occurs in which no atoms rearrange to form a new substance

What we see here is that a triatomic molecule(each containing two atoms shown in white and one atom in red) being closely packed in the first case. On the subsequent change, this molecules move far apart from each other. The molecules themselves do not dissociate and each such molecule again has three atoms(two white and one red).

So, there is no chemical change as there is no change in any chemical composition of the substance. Therefore, we can very easily eliminate options (A), (B) and (C).

This must then be a physical change. There is no change in the chemistry of the substance and the first substance simply loses the intermolecular forces which bind the molecules together to form a new substance.

Again, the new substance formed is not a new compound as both the substances have the same chemical composition.

It is also to be noted that in the physical change, it is the molecules that rearrange in a new fashion to form the new substance and not the atoms themselves. If the atoms would have rearranged then the change would have been a chemical change.

Hence the correct option is:

(D) A physical change occurs in which no atoms rearrange to form a new substance.