Since the early history of the United States, Amerindians, AfricanAmericans, and European Americans have been classified as belonging to different races. Efforts to track mixing between groups led to a proliferation of categories, such as mulatto and octoroon. The criteria for membership in these races diverged in the late 19th century. During Reconstruction, increasing numbers of Americans began to consider anyone with "one drop" of known "Black blood" to be Black, regardless of appearance.3 By the early 20th century, this notion was made statutory in many states.4 Amerindians continue to be defined by a certain percentage of "Indian blood" (called blood quantum). To be White one had to have perceived "pure" White ancestry. The one-drop rule or hypodescent rule refers to the convention of defining a person as racially black if he or she has any known African ancestry. This rule meant that those that were mixed race but with some discernible African ancestry were defined as black. The one-drop rule is specific to not only those with African ancestry but to the United States, making it a particularly African-American experience.
What did efforts to track mixing between different groups lead to?
a proliferation of categories

Chopin's successes as a composer and performer opened the door to western Europe for him, and on 2 November 1830, he set out, in the words of Zdzisaw Jachimecki, "into the wide world, with no very clearly defined aim, forever." With Woyciechowski, he headed for Austria, intending to go on to Italy. Later that month, in Warsaw, the November 1830 Uprising broke out, and Woyciechowski returned to Poland to enlist. Chopin, now alone in Vienna, was nostalgic for his homeland, and wrote to a friend, "I curse the moment of my departure." When in September 1831 he learned, while travelling from Vienna to Paris, that the uprising had been crushed, he expressed his anguish in the pages of his private journal: "Oh God! ... You are there, and yet you do not take vengeance!" Jachimecki ascribes to these events the composer's maturing "into an inspired national bard who intuited the past, present and future of his native Poland."
Who did Chopin leave for Austria with?
Woyciechowski

The division between the two is often not clear and is often politicized in disagreements within a government over a treaty, since a non-self-executing treaty cannot be acted on without the proper change in domestic law. If a treaty requires implementing legislation, a state may be in default of its obligations by the failure of its legislature to pass the necessary domestic laws.
What type of treaty cannot be acted on without the proper change in domestic law?
a non-self-executing treaty