The words chance, chants sound the same but have different meanings and spellings. Why do chance, chants sound the same even though they are completely different words?
The answer is simple: chance, chants are homophones of the English language.
The unknown and unpredictable element in happenings that seems to have no assignable cause.
A force assumed to cause events that cannot be foreseen or controlled; luck: Chance will determine the outcome.
The likelihood of something happening; possibility or probability. Often used in the plural: Chances are good that you will win. Is there any chance of rain?
An accidental or unpredictable event.
Plural form of chant.
Third-person singular simple present indicative form of chant.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").