What factors led to the new imperialism of the 1800s?

The New Imperialism was caused by several economic, political, social and technological factors.  

The Ecomic factors were the need for natural resources and the need to expand  the territory to the growing population and the markets as the economies gained strenght from the Industrial Revolution.

The Social factors were the need to spread Christianity and share the Western Culture  as well as the belief in Social Darwinism.

The Political factors were the need for merchants and naval ships, security and nationalism.

And finally, the technological factors were the advances in medical knowledge, weponry and overseas travel.