The Official Guide to the MCAT Exam, page 139 number 4!

[WhiteWashed]

---

Members don't see this ad.

What is the effect on the sea level when icebergs melt in the ocean??

A. sea level rises because of th eincrease of liquid from the melted ice.
B. Sea level lowers because of the lower salinity of the freshwater added to the sea.
C. Sea level remains approximately the same because of a floating iceberg displaces its weight of water.
D. Sea level rises because the local temperature of the water is lowered.


Sooo pretty much a or c....what would you guys choose?

 

[LaurenMCAT]

Hi WhiteWashed

I LOVE this question!

And you're on the right track - yes, the answer is either a or c 😉 Now - what do you know that can PROVE which one it is?

BTW, someone asked a nearly identical question in another thread:
http://forums.studentdoctor.net/showthread.php?t=778834

 

[WhiteWashed]

Hi WhiteWashed

I LOVE this question!

And you're on the right track - yes, the answer is either a or c 😉 Now - what do you know that can PROVE which one it is?

BTW, someone asked a nearly identical question in another thread:
http://forums.studentdoctor.net/showthread.php?t=778834

I hate this question hahaha. I chose A, some of the iceberg is above the water since the density of ice is less than the density of water. Density of ice=.92, density of water=1. So .08 is above the water, not displacing its volume of water. When the iceberg melts the above portion of the iceberg will displace its volume....thus raising the level of the ocean higher than it was before...by .08.

well that was my logic....FAIL i guess....

 

[LaurenMCAT]

I hate this question hahaha. I chose A, some of the iceberg is above the water since the density of ice is less than the density of water. Density of ice=.92, density of water=1. So .08 is above the water, not displacing its volume of water. When the iceberg melts the above portion of the iceberg will displace its volume....thus raising the level of the ocean higher than it was before...by .08.

well that was my logic....FAIL i guess....

You should see my classroom when we get to this question during the Physics 3 lesson (I think that's the one) - after discussing buoyancy thoroughly, but before explaining the answer to this one - I have the class get into groups and duke it out amongst themselves. The debate gets intense sometimes...hahahaha Even if they get the answer right, I still make them prove it. So...you're in good company!

Do the explanations from the other thread make sense??

 

[WhiteWashed]

You should see my classroom when we get to this question during the Physics 3 lesson (I think that's the one) - after discussing buoyancy thoroughly, but before explaining the answer to this one - I have the class get into groups and duke it out amongst themselves. The debate gets intense sometimes...hahahaha Even if they get the answer right, I still make them prove it. So...you're in good company!

Do the explanations from the other thread make sense??

Honestly, I always thought the volume of the object submerged is the same as the volume of liquid submerged. So if something is half way submerged, it is only displacing half of its volume of water...right???

 

[WhiteWashed]

Honestly, I always thought the volume of the object submerged is the same as the volume of liquid submerged. So if something is half way submerged, it is only displacing half of its volume of water...right???

is this he right logic??

 

[Reaction]

I think it is A because water has more density in its liquid form than in its ice form. =] Good Luck on the exam!

 

[apumic]

Honestly, I always thought the volume of the object submerged is the same as the volume of liquid submerged. So if something is half way submerged, it is only displacing half of its volume of water...right???

Yes, this is Archimedes' Principle. If a 1 cm^3 block is halfway submerged, it displaces 0.5 mL of water (0.5 cm^3). When floating in water, the 1 cm^3 block displaces an amount of water equal to its total weight. If the 1 cm^3 block has d=1.00 g/mL (which, it just so happens, is also the density of water), the 1 cm^3 block will displace 1 g of water (1 cm^3=1 mL*1.00 g/mL=1 g). As a result, the block is fully submerged. When the iceberg melts, its density rises to that of water. Simultaneously, the area displaced by the iceberg becomes displaced with melted iceberg (i.e., water). Since the iceberg previously displaced the amount of water equal to its total weight (which is now liquid water), we can set our weights equal and know that the volume must be equal to the volume previously displaced in the water (because the mass of the iceberg = mass of water displaced by iceberg).

 

[LaurenMCAT]

Yes, this is Archimedes' Principle...Simultaneously, the area displaced by the iceberg becomes displaced with melted iceberg (i.e., water). Since the iceberg previously displaced the amount of water equal to its total weight (which is now liquid water), we can set our weights equal and know that the volume must be equal to the volume previously displaced in the water (because the mass of the iceberg = mass of water displaced by iceberg).

Yep! So our answer is C.

 

[TwoPaddles]

is this he right logic??

Yeah that's the Archimedes' principle.