A sealed beaker of what you are told is aqueous nickel sulfide was given to you by the local chemist and you put it on the window sill. Ater a tew days, you notice that the mixture is getting thick toward the bottom. What is the nature of the initial nickel sulfide mixture, assuming that the temperature on the sill remained approximately constant? a) It is a gas. b) It is a colloid. c) It is a solution.