Solution formation is primarily a physical change. When a solute dissolves in a solvent to form a solution, the individual particles of the solute separate and disperse throughout the solvent, but the chemical composition of the solute remains unchanged.
For example, when you dissolve salt in water, the sodium and chloride ions break apart, but they do not react chemically with the water molecules. Instead, they remain in their ionic form, just spread out more evenly throughout the water.
This process is reversible; if you evaporate the water, the salt can be recovered in its original form. This is a key characteristic of physical changes, as opposed to chemical changes where the original substances would be transformed into new substances.
In summary, solution formation involves the physical mixing of substances while leaving their chemical identities intact, thereby classifying it as a physical change.