What were the causes and effects of the first Opium War?

Britain won Hong Kong

Essentially Britain wanted to sell opium to the people of China. At this time China was being slowly ripped apart by european countries using imperialism, much like Africa. After China denied Britain the right to sell opium to its people, Britain declared war and then promptly won 3 years later. The British received the island of Hong Kong and established 5 treaty ports, where they could essentially trade for free.