PRIMARY SOURCES
When historians talk about evidence, they often mean primary sources. Primary sources (diaries, letters, speeches, newspaper accounts, artifacts, visuals of real events, etc. created during the time period being studied) can offer rich and unique insights into your topic. Thousands of primary documents have been digitized and can be found online on university, government and museum websites. The Bentley Library also has collections of these documents in printed source books.
MIT High School Chemistry (Open access to lectures and videos series from the Massachusetts Institute of Technology (MIT))