Well, because the energy left the system and it dispersed throughout the surroundings, that means the entropy of the surroundings increased in this particular case, and in this case, we can define what the entropy is in terms of the amount of energy that's left the system and the temperature of that particular system. So the way that we define entropy in physics is the change in entropy of the surroundings, which is a positive value as long as entropy left our system is equal to the quantity of entropy, the quantity of energy that left the system as a result of heat divided by the temperature given to us in Kelvins. Now, the negative sign simply means when the enthalpy when the heat basically flows out of the cell, when the energy is absorbed by the surroundings, this system loses energy, but the surroundings gains that energy. And so our delta S of the surroundings will be a positive value. That's why we have this negative value here. So by using this definition of entropy and by using the second law of thermodynamics, we can basically derive the equation for Gibbs free energy that we can use to basically determine whether or not a reaction is spontaneous.