Within the earth's core, which is iron, pressure increases with depth

This question is an Assumption type . If we keep P for pressure, T for melting temperature and D for depth from the surface, we have
Higher D --> Higher P,(1st line)
Higher P --> Higher T,( 1st line)
and they can determine P and T for any depth (D).

Think like this. If they knew exact temperature, they should know the pressure --> they should have knowledge on the depth. So there's your answer.

Give kudos if you find the explanation useful.

Argument:- Within the earth's core, which is iron, pressure increases with depth. Because the temperature at which iron melts increases with pressure, the inner core is solid and the outer core is molten. Physicists can determine the melting temperature of iron at any given pressure and the pressure for any given depth in the earth. Therefore, the actual temperature at the boundary of the earth's outer and inner cores--the melting temperature of iron there--can be determined, since_______.

The correct answer choice is "A" and my explanation as follows:

Option A states "a) the depth beneath the earth's surface of the boundary between the outer and inner cores is known"
The highlighted portion above in the argument states that for a "given" pressure / depth it is possible to determine temperature therefore the assumption that would logically complete this argument is that either or both of these parameters are "given" or in other words "known".

Kudos if you think this explanation most logically completes the choice of answer

Hi guys!

I have a question regarding the argument.
Context: Earth's core is iron.
1st premise: +Depth (D)-> +Pressure (P)
2nd premise: +P --> +Temperature (T) at which Iron melts
Based on this facts, the Intermediate Conclusion says that Earth's inner core is solid and the outer is molten.

However, according to the facts, the inner core should be molten and the outer one solid because D is higher in the inner core, so is P and T = inner core is molten and outer core might be solid.
I spend a lot of time trying to understand this apparent contradiction in this argument, in which the author takes only one position.

Is my understanding correct??

I appreciate your help in advance. Thanks.

A is the correct choice - If physicists know the depth of the boundary between inner and outer cores, they can also determine the temperature at the boundary.
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This is actually a straight forward unless you miss the last few words in option A. Knowing the depth will help us with figuring out the pressure, which is directly related to temp.

Option C, talks about the co-relation between pressure and outer core.

Hi Rumikido,

You got me thinking for a minute and I had to reread the argument

I have highlighted the glitch in your understanding. Please compare what you wrote to what is written in the argument (highlighted part)-


Within the earth's core, which is iron, pressure increases with depth. Because the temperature at which iron melts increases with pressure,the inner core is solid and the outer core is molten. Physicists can determine the melting temperature of iron at any given pressure and the pressure for any given depth in the earth. Therefore, the actual temperature at the boundary of the earth's outer and inner cores--the melting temperature of iron there--can be determined, since_______.

Can you see that they both are opposite?

Rest of the logic structure is beautifully written.

The logic shared by others in option A, hence, helps in supporting the conclusion.

I hope this helps.

Aiena.

generis VeritasPrepKarishma GMATNinja




Could the re-framed version of (C) made it OA?
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Check this presentation. It will help explain it

https://prezi.com/j_hhbvcahu49/why-is-t ... re-liquid/

The most important part in this question is to understand the question stem properly. Once you understand whats given then selecting the answer choice becomes straight forward.

Given:-
1) Pressure increases as we go inside the earths core.
2) Temperature increases when pressure increases.
3) Iron melts when temperature increases.

The last part of the question says,
"Physicists can determine:-
A) the melting temperature of iron at any given pressure" (same as 2 above)
B) the pressure for any given depth in the earth. (Same as 1 above)

Therefore, the actual temperature at the boundary of the earth's outer and inner cores--the melting temperature of iron there--can be determined, since_______."

Temp is related to pressure and pressure to depth. So the missing link which will connect the two is reproduced by option A in a straightforward way:-

a) the depth beneath the earth's surface of the boundary between the outer and inner cores is known - this will help the physicists in identifying the pressure!!
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Premise:
Pressure within the earth's iron core increases with depth. Because the melting temperature of iron increases with pressure, the inner core is solid and the outer core molten. Physicists can determine iron's melting temperature at any pressure and the pressure it is under at any depth.

Pre-thinking:
What further premise, combined with the information provided, would support the conclusion that physicists can determine the temperature at the boundary between the outer and inner cores? Since physicists can determine iron's melting temperature at any pressure and the pressure it is under at any depth, they must be able to determine its melting temperature at any depth. The temperature at the boundary between the inner and outer cores must exactly equal the melting temperature there, since that is the boundary between the molten and solid parts of the core. To determine the temperature at the boundary, therefore, it would suffice to know the depth of the boundary.

A- Correct. If physicists know the depth of the boundary between the inner and outer cores, they can determine the temperature at the boundary.

Official Answer:-

Argument Construction

Situation: Pressure within the earth's iron core increases with depth. Because the melting temperature of iron increases with pressure, the inner core is solid and the outer core molten. Physicists can determine iron's melting temperature at any pressure and the pressure it is under at any depth.

Reasoning : What further premise, combined with the information provided, would support the conclusion that physicists can determine the temperature at the boundary between the outer and inner cores? Since physicists can determine iron's melting temperature at any pressure and the pressure it is under at any depth, they must be able to determine its melting temperature at any depth. The temperature at the boundary between the inner and outer cores must exactly equal the melting temperature there, since that is the boundary between the molten and solid parts of the core. To determine the temperature at the boundary, therefore, it would suffice to know the depth of the boundary.

Correct Answer is option A: If physicists know the depth of the boundary between the inner and outer cores, they can determine the temperature at the boundary.
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The question can be solved if we look at it in an a mathematical way. If we know pressure we can find the temperature.

Temperature is a function of pressure. In other words, we can know the temperature given that we know the pressure. Say for example temperature is in an equation form such as Temperature = Pressure + 20 (1)

Pressure is a function of depth. In other words, we can know the pressure given that we know the depth. Say for example pressure is in an equation form

Pressure = Depth + 10 (2). If we know the value of depth, we can figure out the value of Pressure.

From (2) we can substitute in (1) to find the temperature.

Answer choice A

Bunuel,

Can this tagged to " Complete the Passage " Section
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Done. Thank you.
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Hey adkikani
When u read the argument carefully u will realize that we are looking for a reason as to why they will be able to know the temperature at the boundaries of inner and outer cores.

What if they do not know the depth at which the boundaries are? Then what is the use of being able to measure depth and pressure at any depth? If we dont know depth of boundaries then how will we even know their pressures and temperature?

So we need the statement A for the argument to hold true.
Also, to answer ur question, C wont become OA even if u modify it.


Hope it helps!

The passage states on line 2 that temperature at which iron melts increases with pressure.Please note it is the melting point of iron and not temperature. Hence, as pressure increases near the core, iron can withstand higher temperatures and still be solid.

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Quote:

Which of the following most logically completes the argument below?

Within the earth's core, which is iron, pressure increases with depth. Because the temperature at which iron melts increases with pressure, the inner core is solid and the outer core is molten. Physicists can determine the melting temperature of iron at any given pressure and the pressure for any given depth in the earth. Therefore, the actual temperature at the boundary of the earth's outer and inner cores—the melting temperature of iron there—can be determined, since_______.

Our argument states that since we know temperature of iron increases of pressure AND our amazing physicists can determine the “melting temperature of iron” given any pressure OR given any depth. We can safely conclude that we can assess the actual temperature since we have one or both of the pieces of information.

(A) the depth beneath the earth's surface of the boundary between the outer and inner cores is known
Hello, well, if we know the depth and that physicists can “determine melting temperature … at any given pressure and the pressure for any given depth”, I’d say we’re pretty golden here.

(B) some of the heat from the earth's core flows to the surface of the earth
This answer choice is not relevant. We need an answer choice that talks about our knowledge of depth or pressure. ):

(C) pressures within the earth's outer core are much greater than pressures above the outer core
Again, this distinction is irrelevant. It’s great that we know how the pressures are relative to each other, but to calculate actual temperature, we need some SOLID numbers!

(D) nowhere in the earth's core can the temperature be measured directly
This answer choice discusses why we can’t measure temperature, while our argument states that we can measure it with other factors, such as pressure and depth numbers.

(E) the temperatures within the earth's inner core are higher than in the outer core
Again, similar to (C). Relative differences are not solid numbers! ):
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Situation Pressure within the earth’s iron core increases with
depth. Because the melting temperature of iron increases with
pressure, the inner core is solid and the outer core molten. Physicists
can determine iron’s melting temperature at any pressure and the
pressure it is under at any depth.
Reasoning What further premise, combined with the information
provided, would support the conclusion that physicists can determine
the temperature at the boundary between the outer and inner cores?
Since physicists can determine iron’s melting temperature at any
pressure and the pressure it is under at any depth, they must be able
to determine its melting temperature at any depth. The temperature
at the boundary between the inner and outer cores must exactly
equal the melting temperature there, since that is the boundary
between the molten and solid parts of the core. To determine the
temperature at the boundary, therefore, it would suffice to know the
depth of the boundary.
A. Correct. If physicists know the depth of the boundary between the
inner and outer cores, they can determine the temperature at the
boundary.
B. The fact that some heat flows from the core to the surface is too
vague to help in determining exact temperatures anywhere.
C. The difference in pressures between the outer core and the region
above it is only vaguely described here and is not clearly relevant to
the temperature at the boundary between the outer core and the
inner core below it.
D. An absence of information would not be helpful in determining the
temperature at the boundary between the outer and inner cores.
E. This information is not sufficiently specific to show that the
temperature at the boundary between the outer and inner cores can
be determined.
The correct answer is A.

Hi avigutman - I did select A but my question is the significance of the two dashes in the red. Specifically -

When you read the yellow statement , is the author himself/ herself telling us that the temperatures ARE THE SAME (At the boundry) ? OR is that an inference to be made by the reader ?

I couldn't tell if the author himself/herself was stating plainly if these two temperatures were the same or not (at the boundry)