Suppose we have our system where the red molecules are water solid molecules and the red and orange molecules or the molecules spoken about here, are the reactants. So notice that the red molecule is in a cage of solid molecules and before it leaves, they make many collisions with the water cage. Eventually, however, it will bounce out. And if it bounces into another cage where this origin molecule is present, then it will react to former products. But otherwise, if it jumps into another cage that doesn't have another reactor molecule, it will continue balancing. And this greatly slows down our reaction in liquid and increased space.