#19 - Spectroscopic analysis has revealed the existence of

[HowardQ]

Hi

I still don't quite get how there can't be anything in between CH4 and CO. Where in logic game logic, the conclusion states in order of decreasing aboundance, N2 Co CH4, which indicates it's possible to include some components in between. The passage did not mention that there are only 3 components in the atmosphere also. From the method of spectroscopic analysis I also don't see any reason they could conclude what the atmosphere doesn't have. I understand how answer C works in the argument, but cannot find proof in the passage that this must be the case.


thanks

[Adam Tyson]

When the astronomers concluded that the components of the atmosphere are those three things, they didn't say that they "include" those things. That would allow for there to be more. Instead, they said "the components of Pluto’s atmosphere are (emphasis added) nitrogen, carbon monoxide, and methane". That means the atmosphere is made of ONLY those things. They have to be assuming that there is nothing else! That's just the nature of the language here.

If I say "the people who live in my house are myself, my wife, and my son", that means that those are the ONLY people who live there. If my mother also lived with us, I would have had to either mention her or else qualify my original claim like "the people who live in my house include..." or "some of the people who live in my house are...". To do otherwise would mean the original claim was false.

In a logic game, to use your example, the scenario typically tells you that there are more variables than just those in that sequence. If the game said "the members of the group are X, Y, and Z, in that order" then that would mean those were the ONLY members of the group.

I hope that helps!

[dbrowning]

I eliminated answer C because it said “substance” instead of “gas”. At least conceptually, you could have a frozen substance that vaporizes but is not a gas, like nitrogen, that could exist in an atmosphere. Why did this distinction not matter in this case? Or was I just being overly narrow in how I thought about this question?

[James Finch]

Hi D. Browning,

First off, this might be a vocabulary issue, as vaporization is the point at which a liquid changes state into a gas; by definition, anything that is vaporizing is becoming a gas. The stimulus skips a step, in that the ice would melt into a liquid first and then finally vaporize into a gas, but the point remains.

This a clear Supporter Assumption question, where the missing pieces are the rate at which the three types of ice vaporize, and that they are the only three types of ices that would vaporize on Pluto's surface. A sufficient assumption would tell us that they all vaporize in the order given in the conclusion, but we're looking for a necessary assumption. If we split the sufficient assumption in half, from nitrogen>carbon monoxide>methane to nitrogen>carbon monoxide and carbon monoxide>methane, we can come up with two solid Prephrases for a necessary assumption, as both are necessary but neither one, on its own, is sufficient to prove the conclusion.

Only (C) even deals with vaporization rates, so that's the only answer choice worth looking closely at. What it is saying is that there is nothing between the carbon monoxide>methane vaporization rate, which gives us that carbon monoxide vaporizes more readily than methane and that nitrogen can't be in between the two either, allowing it to still vaporize more easily than carbon monoxide (or possibly less readily than methane). Using the Assumption Negation technique allows us to see that if there were another ice, be it nitrogen or a mysterious fourth substance, that would invalidate the conclusion's assertion that there are only the three components in Pluto's atmosphere and that they exist in the order given.

Hope this clears things up!

[a19]

Hey! Sorry to beat a dead horse so to speak. But I wanted to revisit A to see if my logic in eliminating it is correct.

Okay, so from the stimulus we know that we have nitrogen, carbon monoxide and methane on the surface of Pluto in ice form. But we are not told how much of each ice is on Pluto, nor are we told relevant rates of vaporization. Rather, we are only told that the atmospheric composition is dependent on rate of vaporization. There could either be a HUGE amount of nitrogen, which vaporizes slowly, still making up the most abundant resource in atmosphere. Or we could have a tiny amount of frozen nitrogen which vaporizes at lightening speed, still making up the most abundant resource in the atmosphere. In some ways, this question/answer choice seems to test my understanding of rates/percentages/distribution... Is this reasoning correct?

I get the answer is C. Its actually a very plain, boring assumption, which when in testing mode is easy to mark off as too easy. Of course there is no other substance on Pluto that can vaporize at the specified rate, else the entire argument would be false.

Also, for D, I feel like its kinda what the argument is already saying. Literally, we have ice on this planet and the gas corresponds to the ice. I dont think it is an NA. Is that thought process right as well?


Thank you!!!!

[Rachael Wilkenfeld]

Hi A,

Great work. For answer choice (A), you are absolutely right that the answer choice doesn't help us without knowing more about the readiness of vaporization. There are multiple ways to reach abundance, just as you describe.

One of the most frustrating stages of LSAT study can actually be the stage where things start to click! Answer choices feel too obvious, and you are tempted to eliminate them because it can't be THAT easy. Boring, accurate answers are the name of the game. Especially in certain question types, like assumptions, where you have a very clear test for the answer choices, don't shy away from something that seems too accurate.

Answer choice (D) is problematic because it's more than we would need. We don't need to know that is the only way to have nitrogen in the atmosphere. There could be other ways to have nitrogen in the atmosphere of other planets. For example, Venus could have a totally different process of atmospheric development. We don't know, and we don't need to. We just need to know about Pluto.

Hope that helps!
Rachael

[alacantaramac]

Hi powerscore,

As many others have, I also fell for A.
What got me was the very last phrase of the conclusion 'in order of decreasing abundance'; it led me to think that it would 'necessitate the assumption' that the order is in fact correct.
I understand that the correct answer C links 'revealed the existence of ~~~' and 'components are ~~~'.
Thinking of it as a flaw, it would be subject to question if one were to conclude the only components of an entity from evidence of having found those components.

I have found that phrases like 'in order of decreasing abundance' are exactly what the test makers enjoy slipping into the stimulus to tempt us into incorrect answer choices like A.
Upon my review, I realized that I should have identified the jump in reasoning (flaw, 'found'-->'composed of only') then stuck with the definite flaw I identified.
Of course, through further inspection, it would also be clear that the amount of frozen material is irrelevant, as the rate of its vaporization is all that matters.

I have some thoughts from having come across a handful of these stuctures (an irrelevant phrase separated from the conclusion with a comma)

Another question that tripped me up in a similar way was Question 17 Section 2 (Lawhub ordering) of PrepTest 90+

The stimulus states that 'costs of transporting' --> 'not economically feasible to colonize Mars'
This question also provides two answer choices that fill the gap for what I presume to be two popular possibilities: costs>benefit & transporting is necessary
In this case, the power 'transportation' has over 'cost' is greater since, no matter the cost, if transportation does not occur, cost is irrelevant.
In retrospect, both questions have an element of new concepts within the stimulus (why are we suddenly making conclusions about the components of the atmosphere, why would transportation pop up),,, and may not be similar at all, other than having two contenders

As I write this I am starting to think that maybe I am reducing every Assumption question to finding that 'new' concept...?

The conclusion that I wanted to land at was that I found sticking to the point at issue and not falling for details important

please send help

[Adam Tyson]

Many Assumption questions ARE all about finding that "new" element, alacantaramac, so you are on the right track. If the conclusion brings up a new idea, then the assumption is that the premises are somehow connected to and support that new idea. The other approach to assumptions is to identify a flaw in the argument and then recognize that the author must have assumed there was no such flaw. They would defend the argument by saying that the problem you found is not really a problem.

Here's how that translates to prephrasing the correct answer: if when you first read the argument, you see some new idea appearing in the conclusion, start by prephrasing something that connects the premises to that new thing. If you read the argument and think to yourself "there's a flaw here," then prephrase something that removes that flaw.

One more thing I want to mention: you said that the author's claim about the relative abundance of the gasses "would 'necessitate the assumption' that the order is in fact correct." That's actually not an assumption, or at least not the kind of assumption that we find on the LSAT. The author SAID that was the order, but an assumption is something the author did NOT say. It's true that all arguments are based on the assumption that all the premises are correct and that the conclusion follows logically from those premises, but the LSAT never tests that particular set of assumptions. We are always looking for something more than just "they assume they are correct." Look for that gap in the argument or that problem, and make that the focus!