Now, what about the second law of thermodynamics? Well, the second law of thermodynamics is commonly described by using a term known as entropy. And entropy is this quantity that we use to basically measure the amount of randomness or disorder that is found in our universe. Now, what exactly does the second law of thermodynamics tell us? Well, what it tells us is every time a real reaction takes place, be it physical or chemical, the change in entropy of the universe is always positive. So the entropy of the Universe increases in any real reaction.