What is the isotope of Be?

Neither model is able to show the reactivity of potassium.

In reversible reaction chemistry equilibrium is attained when the forward and reverse reactions are taking place at the same rate, thus, the concentrations of reactants and products remain the same. a reversible reaction is a chemical reaction where the reactants form products that, in turn, react together to give the reactants back. in irreversible reactions on the other hand, the reactants react to form the products, which cannot revert back into reactants.

I'd say your answer would be the sides of a metal pan become hot when the pan is placed on the stove burner