What are the entropy and enthalpy?

Enthalpy is the energy of the molecules. It cannot be measured, although CHANGE in enthalpy of reactions can be measured. It's simply heat energy. Exothermic reactions have anegative enthalpy change(which means energy of the products is lower than that of the reactants). Endothermic reactions have a positive value(energy of products is higher than that of the reactants). Entropy, on the other hand, is the degree of disorder. It's the measurement of how disordered a substance is. For example, particles in a solid are regularly arranged, so they are less disordered, and have a low value of entropy. Gases have much higher entropies. Entropy of an individual compound can be measured/calculated.