give two examples of how nationalism started revolutions across europe in 1848?

The two examples of how nationalisms stared revolutions can be placed in:

1. The arousal of educated, liberal middle-classes, made up of industrialists, businessmen, professionals in which the ideas of national unity, following the abolition of Aristocracy, gained popularity. In the economic sphere, there was a strong demand of  freedom of marketsand the abolition of state-imposed restrictions on the movementof goods and capital.

2. Tensions that the 1815 "New Conservatism" created, since these regimes were autocratic, by imposing censorship laws to control what was said (for example in newspapers), becoming one of the major issues taken up by nationalist liberals.

they believed democracy was worth the fight