When discussing this question, it's worth being aware of the degree to which industrialization shaped the nineteenth and early twentieth centuries. Imperialism itself existed within the context of industrialism, and we can add to that the impact of these transformations on reshaping society.

At the same time, one should not underestimate the degree to which large-scale industrialization introduced elements of instability within the social structure. The creation of a large-scale working class as well as the spread of ideologies such as Marxism and socialism among those working classes introduced elements of radicalism. From a purely pragmatic calculus, going to war provided a means of patching over the divisions present within those countries. Energies potentially dangerous to the status-quo could be channeled in an alternative direction.

At its core, the First World War was a war fought by fully industrialized nations. Technologically, it featured the use of chemical warfare, barbed wire, machine guns, airplanes, submarines, and so on. Additionally, it's worth factoring in the ways in which industrial technology shaped the mobilization of the war (for example, in the use of railways).

Meanwhile, when looking toward the impact of imperialism, it's worth noting the degree to which international rivalries shaped the lead-up to the war. The competition for colonies, influence, and prestige did much to spark tensions back in Europe. This would prove critical in sparking World War I.

Industrialization played a large role in the onset of World War I.  Nations could build larger ships faster through the development of cheap steel.  Nations could also mass-produce bullets and other weapons of war as never before, along with more powerful explosives.  Many of the poison gases used in World War I, such as chlorine, were industrial waste products from some other less lethal process.  Nations formed trade rivalries, and the nations of Europe were worried about losing status to their adversaries.  Industrialization also led Europeans to constantly upgrade their rail networks; these rail networks could also be used in army mobilization schedules.  

Imperialism also played a role in the onset of World War I.  Britain and France nearly got into a skirmish in Africa over the Fashoda incident.  Kaiser Wilhelm II spoke in favor of the Boers, which drew him a sharp rebuke from his grandmother, Queen Victoria.  Russia had designs on Turkish land, especially Constantinople itself since this was the birthplace of the Orthodox Church.  Germany sought to gain more colonies, and it strengthened its navy.  This alarmed Britain, creating an arms race.  This heightened tensions and helped cause World War I.