Baking soda in water is indeed a solution, not a compound. When you add baking soda (sodium bicarbonate) to water, it dissolves and its molecules disperse and mix uniformly throughout the water. The resulting mixture is a solution, where baking soda is the solute, and water is the solvent.

A compound, on the other hand, is a pure substance formed by the chemical bonding of two or more different elements in a fixed proportion. When baking soda dissolves in water, its sodium and bicarbonate ions separate and become surrounded by water molecules, resulting in a homogeneous mixture of solute particles (baking soda) dispersed throughout the solvent (water). This does not form a new chemical compound; it remains as sodium bicarbonate dissolved in water.

Solutions are characterized by their ability to be separated into their components through physical means, such as evaporation or distillation. For instance, if you boil the baking soda solution, the water will evaporate, leaving behind the solid baking soda. Compound, on the other hand, cannot be easily separated into their constituent elements without chemical reactions.