union
working together as states (think of a map of the US and how all the individual states are working as a nation)
justice
to be fair (think courts)
domestic tranquility
to have peace here in the US (think police)
common defense
to protect us from other nations (think military)
general welfare
to look after the the common good (think public works: i.e. roads, sewer and water)
liberty
to be free (think about your protected rights)