How do chemical indicators work? explain

Chemical indicator, any substance that gives a visible sign, usually by a color change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution.

a force of 500                  

african americans demonstrated their newly found freedom by relocating often in search of relatives whom they had been separated from during slavery. others established schools to educate freed people and they built institutions such as churches and political organizations to advocate for their rights.