What happens to water activity when solutes are added to a solution?

When solutes are added to a solution, water activity decreases. This can be explained by considering the nature of solutes and their interaction with water molecules. Water activity, which is a measure of the availability of water for chemical reactions and biological processes, is affected by the presence of solutes.

When solutes enter a solution, they interact with water molecules and occupy space around them. This leads to a situation where fewer water molecules are available to participate in reactions or biological activities because some of them are bound to solute particles. As a result, the effective concentration of free water decreases, leading to a lower water activity. This concept is crucial in fields such as microbiology and food science, where understanding water activity helps predict microbial growth and the stability of food products.