Contrary to misconceptions, ameliorate and alleviate do have differences. While ameliorate means to actually improve a situation, alleviate means to relieve the stress of the situation, make it more tolerable.
example: To ameliorate the bitter soup, one might add other ingredients, improving the soup itself. To alleviate the bitter soup, one might distract the self while eating it, talking to friends, holding the nose, eating other foods, making it easier to consume. None of this lessens how bitter the soup actually is. It just alleviates the discomfort of consuming it.