#14 - A cup of raw milk, after being heated in a microwave

[Administrator]

Complete Question Explanation

Question #14: Weaken. The correct answer choice is (E)

The argument contains causal reasoning, because the conclusion attempts to attribute a phenomenon (difference in concentration of lysozyme) to a particular cause—microwaves:

• Premise: When you heat raw milk in a microwave to 50'C, it contains half of its initial concentration of lysozyme.
  Premise: When you heat raw milk on the stove to 50'C, it contains nearly all of its initial concentration of lysozyme.
  
  Conclusion: Microwaves (cause) Destroy lysozyme (effect)

As with many causal arguments, this one ignores the possibility of an alternative cause. What if the depletion of lysozyme has nothing to do with microwaves? Maybe microwaves do something else to the milk that destroys its lysozyme?

Answer choice (A) is incorrect, because it is consistent with the information in the stimulus. If heating the milk to 50'C destroys half of the lysozyme, it's possible that heating it to a boiling temperature would destroy all of it. There is no reason to believe that this would weaken the argument.

Answer choice (B) is incorrect, because the issue is not whether the lost enzymes can be replaced, but rather why they are lost in the first place.

Answer choice (C) is incorrect, because it only stands to reason that liquids heat up faster when exposed to higher temperatures. This does not explain the difference in the amount of lysozyme observed.

Answer choice (D) is incorrect, because the issue of taste has no bearing on the conclusion of the argument. The question is why microwaved milk has less lysozyme than milk exposed to conventional heat source, not whether this difference affects taste.

Answer choice (E) is the correct answer choice. If heating milk by microwave creates small zones within it that are much hotter than 50'C, then it stands to reason that these pockets will lose lysozyme at a higher rate than the rest of the milk. So, although the overall temperature reached is ultimately 50'C, some of the milk will have been exposed to much higher temperatures, which could have caused its enzymes to break down.

[olafimihan.k]

Please help I've re-read this explanation multiple times but still cannot understand how answer choice E weakens the stimulus? It seems to me that it actually strengthens by explaining how microwaves deplete lysozymes. Am I missing something?

Thanks in advance.

[James Finch]

Hi Olaf,

It sounds like yo umay be conflating "microwave ovens," the appliances that heat food and drinks, and "microwaves," the process of energy transfer by which microwave ovens heat food and drinks. Given that nobody I know ever says "microwave ovens,"
instead using "microwave" to mean the appliance itself (the correct answer, (E) does the same thing), this is totally understandable.

(E) weakens the conclusion by saying that there are zones in microwaved milk that are far hotter than the 50 degrees overall that the milk is at, and that implies that it is the far hotter zones where the lysozymes are being destroyed, not in the rest of the milk. This would then suggest that it isn't the microwaves per se that are destroying lysozymes, but instead that the heat isn't evenly distributed and thus far greater heat in certain spots is the cause, still making heat, and not microwaves, the direct cause of the lysozyme destruction.

Hope this clears things up!

[Dave Killoran]

This problem was covered in detail in Episode 7 of the PowerScore LSAT PodCast. The explanation can be found at the 1:00:53 mark here:

PowerScore Blog, with full timing notes

iTunes

[NeenStudies]

Hello!

This question is still bugging me, I can't seem to move past it. I heard the Podcast to understand it better and I do understand it - in fact while doing the question I chose E but switched to C even when C didn't make sense to me either, it sounded wrong.

Getting to the point of why both of them sounded wrong to me:

(C) said 'a liquid' it didn't say any liquid, which sounded fishy to me. Then it speaks of the speed of reaching 50 degrees which seemed irrelevant but it was enticing to choose because maybe the speed affects how the enzyme is destroyed?

(E) just doesn't make sense to me why it's right because it explains how there is higher temperature involved, but I thought it was wrong of me to presume that a higher heat would cause the destruction of enzymes since i found this a/c to be too broad and using common sense -- which we should try to be careful of using. And if the heat is caused by microwave, how do i treat these two things exclusively? This a/c puzzles me.
Another issue with a/c (E) is because similarly (C) could be right, if conventional heat is slower, then speed of heat is an important factor not microwaves.

I hope I'm making sense!

[KelseyWoods]

Hi Neen!

The conclusion that we're trying to weaken here is "Therefore, what destroys the enzyme is not heat but microwaves, which generate heat." As discussed above, this is a causal conclusion. It is both providing a cause of the enzyme being destroyed (microwaves) as well as denying an alternate cause (the heat). Often with a conclusion like this, you weaken the author's stated cause by strengthening the cause the author is trying to deny. So an answer choice that strengthens the idea that it is heat that is causing the enzyme to be destroyed would weaken the idea that it is something else specific about microwaves that is causing the enzyme to be destroyed.

It also helps to keep in mind the premise that this conclusion is based on. The premise here is that we have two glasses of milk that are both heated to the same temperature (50 degrees Celsius). The milk heated to this temp in the microwave loses half of its lysozyme. The milk heated to this temp via conventional heat doesn't lose its lysozyme. Since both cups of milk reach the same temperature, the author is saying that the heat is not responsible for the difference in the amount of enzymes left in them.

Answer choice (E) strengthens that it is the heat that causes the lysozyme to be destroyed when it is microwaved. Answer choice (E) tells us that certain spots in the milk get much hotter than the 50 degrees Celsius that the overall liquid reaches when it is done microwaving. This tells us that the heat in the two glasses of milk the argument is comparing is not the same. In the microwaved milk, there are some areas that get much hotter than 50 degrees Celsius. This may account for why half of the lysozyme is destroyed. It may be that the lysozyme in the areas that get significantly hotter are destroyed because of the heat. This strengthens the idea that maybe it really is heat that is destroying the lysozyme and, thus, weakens the author's conclusion that the destroyed lysozyme is not due to heat.

Careful with answer choice (C)--it doesn't say that conventional heat is slower. The comparison in answer choice (C) is between two different conventional heat sources--one that is exactly 50 degrees Celsius and one that is hotter than 50 degrees Celsius. This doesn't tell us anything about microwaves or about the potential effects of heat on lysozyme.

Hope this helps!

Best,
Kelsey

[NeenStudies]

Hello Kelsey

I understand this much better now. I would worry about this question in my sleep, but reading it calmly, with the help of your explanation it makes sense why answer choice (C) is wrong . Thank you!

[KLSATForum]

Hello,

When I answered this question, I understood that (E) was the correct answer, but I did not see at first that is was a causal reasoning structure, but I think I got it right by thinking it more as an Error in Composition mistake-parts of the milk were not at 50 degrees even though the milk cup as a whole as at 50 degrees.

Seeing it now as a causal reasoning question makes it easier to see the correct way of answering and better understand why (E) is correct, but can it also be understood as a Error in Composition if the author assumed the whole milk was at 50 degrees in all parts just because the milk as a whole was at 50 degrees? Looking it this way helps me understand this answer. Thanks!

[atierney]

Hi,

So, obviously, we always want you to understand the question and its answer in the manner in which it was intended to be understood and answered. That's part of how you both learn the question-type/type of reasoning, as well as ensure that you will be able to select the correct answer choice on a similar test question. Having said that, I agree with you that there is a presumption of uniform temperature across liquid anytime you give a certain liquid's temperature; I think this might have something to do the smooth transport of energy across liquids, but my hs science memory fails me. Thus, if looking at it that way helps you get the right answer, then you certainly haven't made a mistake!

Regardless, the main idea here is that there might be some reason why heat (or lack thereof) is nonetheless the primary reason for the bacteria's concentration at any given temperature, and the correct answer choice is the one that demonstrates this, regardless of whether though of in a causal way or an error in composition, because even with the recognition of the error in composition, there is still the fact that the heat (in those parts of the whole that are hotter than the whole itself) is causing the bacteria to be eliminated.

Let me know if you have further questions on this.