Question

Adding salt to water makes it salty. Which of the following is true regarding this change?
A.It is a chemical change because a new substance is formed.
B.It is a physical change because the original substances can be recovered.
C.It is a chemical change because there is exchange of heat.
D.It is a physical change because there is a slight change in colour.

Answer 1

Hint:Salt is made up of sodium chloride. It is an ionic compound consisting of positively charged $N{a^ + }$ ions and negatively charged $C{l^ - }$ ions. When salt is dissolved in water it dissociates into its respective cations and anions. Being an ionic compound, it has a high melting point and boiling point.

Complete answer:
Salt is made up of $NaCl$ . It is an ionic compound. As we know ionic compounds are made up of cation and anion. Cations are positively charged species and anions are negatively charged species. Ions have strong electrostatic intermolecular forces that hold the molecule together. Electrostatic force is the attraction between two charged species.
When salt is dissolved in water it dissociates into its respective cations and anions. These ions are surrounded by water molecules. As we know, dissolves like. In water molecules oxygen atoms have partial negative charge and hydrogen has partial positive charge.
When salt is dissolved in water, only ions are formed and no new substance is formed. The colour of the solution does not change. But when we evaporate such a solution then the salt can be recovered again. Such processes in which original substances are recovered are physical processes.
So the correct option is B.

Note:
-Generally salts are ionic in nature and have strong bonds. High amount of energy is required to break them.
-Such ionic compounds have a regular pattern of arrangement of ions in the structure. There is an ordered arrangement of ions.
-Physical processes are reversible and chemical processes are irreversible.