Classify each of the following as a physical or chemical change. For any chemical change list at least one clue to support your answer. a. A copper wire is bent. b. Charcoal burn in a grill. c. Bread dough rises when yeast is added. d. Sugar dissolves in water.

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.