[jsauerland]

So I was following a College Professor's chemistry series, and he directly contradicted himself, and now I'm 100% lost.

https://www.youtube.com/watch?v=ZxGKBrmqTzE&list=PLBwHfJmqJz5h5a6UxWpMrxV-jSlMKNSIn&index=33

At exactly 2:30, he says:
"When a system absorbs energy from its surroundings, we call that endothermic, and it has a positive delta E... In contrast, when a system gives off energy to its surroundings, we call it exothermic and Delta E is negative."

Okay, now to his next video:
https://www.youtube.com/watch?v=H4E_eyLmaKQ&index=34&list=PLBwHfJmqJz5h5a6UxWpMrxV-jSlMKNSIn

"it also asks us to determine whether it is endothermic or exothermic. Now keep in mind this the answer to this question only depends on the value of q. If heat was positive, then its endothermic, and if it's negative then it's exothermic."

So he directly and perpetually contradicts himself. What the heck is the real answer? Is it pos/negative E, or is it pos/negative q?!!?!

[Borek]

we call that endothermic, and it has a positive delta E

If heat was positive, then its endothermic

I don't see any contradiction here, looks to me like he said twice the same.

Note: in both cases he is talking about change of the system internal energy, "heat" in the second case refers not to the increase of the temperature of the surroundings, but to teh heat absorbed by the system. Perhaps that's what confused you?

[jsauerland]

we call that endothermic, and it has a positive delta E

If heat was positive, then its endothermic

I don't see any contradiction here, looks to me like he said twice the same.

Note: in both cases he is talking about change of the system internal energy, "heat" in the second case refers not to the increase of the temperature of the surroundings, but to teh heat absorbed by the system. Perhaps that's what confused you?

The contradiction is that in the second video, he stated that endo/exo was ONLY determined by positive or negative q. In the first video, he claimed that if E is positive or negative, that is how to discover if it is exo endo. Meaning that it is either one or the other. It's either ONLY determined by q, or it's determined by E. That is what makes no sense. Reason being, in the second video, E is positive, but q is negative, but he claims that it's exothermic because q is negative (even though E is positive). As such, positive E can't possibly ALWAYS mean it is endothermic. Why? Because he demonstrated where q is negative, it's exotherm. It can't be both exo and endo.

[Vidya]

"it also asks us to determine whether it is endothermic or exothermic. Now keep in mind this the answer to this question only depends on the value of q. If heat was positive, then its endothermic, and if it's negative then it's exothermic."

So he directly and perpetually contradicts himself. What the heck is the real answer? Is it pos/negative E, or is it pos/negative q?!!?!

E is the internal energy of the system which is the sum of heat and work
ΔE= q + w
Exo and endo are decided by q only ...there are processes which are exo with positive ΔE