Masechet Eduyot, Perek Chet, Mishnah Aleph. This Mishnah will talk about a nevelah, the carcass of a non-kosher animal or an animal that died without proper shechitah (ritual slaughter). The animal, of course, is not allowed to be consumed, but the meat also becomes tameh (not pure). Here we'll talk about the blood: is it treated like the meat or not? The Mishnah says that Rabbi Yehoshua ben Beteira testified that the blood of a nevelah is tahor (pure), even though the meat is not pure. The meat of a nevelah, even in an amount as small as a kezayit (an olive's bulk), is considered tameh. The blood is not tameh unless there's a significant amount of a revi'it (a quarter-log), which is much larger than a kezayit.
We'll also now talk about the parah adumah (red heifer), or any type of sacrament, or any sacred item that is together in one vessel. Rabbi Shimon ben Beteira gave testimony about the ashes of the parah adumah that are together in one keli, in one vessel: if a tameh person touched some of them, even one little piece of ash, then everything in there becomes tameh. The vessel brings all of the items together, brings all of the ashes together, and makes them into one entity. So touching some of them makes all of them impure. We learn from here that when it comes to regular tameh, if a regular tameh person touched part of an item that's within a vessel, all of it becomes impure because it's all one entity. Rabbi Akiva is going to take it one level further. He's going to say that even a person with a weaker level of tum'ah (ritual impurity), a tevul yom (one immersed that day), is also going to make everything impure.
When talking about other types of sacred substances, why there is a difference between them is not really nogea right now. It doesn't really matter why Rabbi Shimon said parah adumah and Rabbi Akiva is saying different things. But the important part is the flour, the incense, the levonah (frankincense), and the coal that were taken from the Mizbeach (altar). When it comes to a tevul yom, if a person at this weaker level of tum'ah touches some of them, all of them become disqualified; all of them become tameh. As long as they're together in one vessel, that brings them together and unites them as one. So therefore, all of them become impure.