1. During exothermic reactions: a. heat is transformed into potential energy b. kinetic energy is transformed into bond energy c. potential energy is transformed into bond energy d. potential energy is transformed into kinetic energy 2. Which of the following are chemical changes? a. mercury has a density of 13600 kg/m3 b. potassium reacts with water c. hammer a nail into a piece of wood d. a rotting apple e. potassium is a soft metal f. evaporation of water g. sublimation of dry ice h. dissolve sugar in water i. a growing flower j. hydrogen is a flammable gas