What did the british government hope would happen by blockading Germany?

The British blockade from 1914-1919 sought to obstruct Germany's ability to import goods, and thus in the most literal sense starve the German people and military into submission.

Explanation:

The British government with their great sea power established naval blockade of Germany straight away on the eruption of war in August 1914, providing a complete list of illegal imports that all but banned American trade with Central Powers, and in early days of November 1914 they decided the North Sea to be war zone.

This operation was named the British blockade (1914-1919) which wanted to block Germany's capacity to import goods from other nations, and thus starve the German people and thereby making military surrender. This marked the start of the "hunger blockade" (a "war of attrition" that remained until Treaty of Versailles was signed in June 1919 by Germany).