In 1839, the british became more imperialistic in china by declaring war and forcing the chinese to sign trade agreements. what was the effect of this action?

Well, one of the effect was the british smuggled a ton of amount of Opium into China and got a lot of its population hooked.
This raged the emperor of China to the point where he declared a war against the Biritsh army known as the opium war

hope this helps