Is evaporation of water a physical or chemical change

Calculate the h3o+ concentration in a solution of acetic acid if the concentration of molecular acetic acid present at equilibrium is 9.97x10^-3 m and k for the dissociation is 1.86x10^-5. ch3cooh(aq)+h2o(> h3o^+(aq)+ch3coo^-(aq)

Which of the following are good traits of a hypothesis? it will be able to be testedit can predict an outcomeit will explain the observationsall of these

Helium decays to form lithium. which equation correctly describes this decay?