IMAT 2011 Q42 [Water Properties]

Which property of water is most important when heat is lost from human skin?

A. dipole properties so salts can dissolve in sweat

B. high specific heat capacity

C. latent heat of vaporisation

D. boiling point of water

E. water density is greatest at 4°C

In this question, we are being asked about the properties of water .

We should have arrived at these questions knowing the meaning of each answer to eliminate OR scale the importance of each of the answers!

This question is critical, as the properties of water are the basis of biology, so we must understand its features, ESPECIALLY to the IMAT!

“Dipole properties so salts can dissolve in sweat” – We know that water has a substantial dipole property due to its shape, one oxygen with 2 electron pairs and two hydrogens, so the polarity is powerful, and water can ionize salt. But how does it affect the heat lost from human skin? We know more solute in a solution increases its boiling point, but how much effect does it have on a 37C human? And Don׳t forget, the question is about HEAT LOST, so increasing the boiling point doesn’t have anything to do with that.

Let׳s read the rest of the answers to find a better choice. High specific heat capacity – DONT BE CONFUSED WITH THAT TWO TERM!

Heat capacity: The capability of a substance to absorb heat energy-specific heat: the amount of heat, in calories, needed to raise the temperature of 1 gram of water by 1 degree Celsius is a property caused by hydrogen bonding among water molecules.

Cambridge, you tricky! The question is about the HEAT LOSS from the human body, so if B were talking about “heat capacity” and not “SPECIFIC heat capacity,” we might have our answer here! Ensure to MEMORISE all of those IMPORTANT terms difference; it is the most important thing to do when studying for the IMAT! High specific heat capacity means it will be harder for water to heat up, so it is probably not our answer!

C) Latent heat of vaporization – Latent heat of vaporization is a physical property of a substance. It is defined as the heat required to change one mole of liquid at its boiling point under standard atmospheric pressure. It is expressed as kg/mol or kJ/kg. When a material in a liquid state is given energy, it changes its phase from liquid to vapor ; the energy absorbed in this process is called heat of vaporization . The heat of vaporization of water is about 2,260 kJ/kg, equal to 40.8 kJ/mol.

Hmm, the energy=heat that is absorbed? Look exactly like our answer! And it is our answer.

Let’s rule out the rest of our answers:

D) boiling point of water – When the human body is 37C, The boiling point of water might be important, but not as much as the latent heat of vaporization.

E) water density is greatest at four °C – Have nothing to do with the heat that is lost from the human skin.

Tip for the IMAT: When going through this tricky question, ask yourself first, “do I know those definitions perfectly? If you do, go for each one in turn and ask yourself.

If X (the answer) is the most important to (Y) the question, in this case, “the heat that is lost from the human skin)

If you are unsure, don׳t stick with one question, rule out some obvious wrong answer, stick a * right next to it, and keep going, extracting as many points as you can from this test.