They gave them opium to get money, because they weren't trading. British were selling Indian opium to the Chinese in order to buy Chinese luxury goods which sounds like fair trade, but they created an addiction epidemic.
Spheres of Influence
A war between the british empire and china Britain overthrew China, resulting in the Treaty of Nanking and the Treaties of Tienstin. This forced Hong Kong Island and Kowloon City to cede to the United Kingdom.
A civil war in southern China, a large revolt against the authority and forces of the Qing Empire in China.
The British were trying to take control of the Chinese imports because china didn't to buy what Britain was selling.
This was meant to drive out all foreigners, remove all foreign influence, and compel Chinese Christians to give up their religion