Which action would involve the greatest transfer of heat?

Question

A. changing the temperature of 1 g of water from 10°C to 90°C

B. cooling 10 g of water from 80°C to 40°C

C. evaporating 1 g of water at 25°C

D. condensing 5 g of steam to liquid water

E. raising the temperature of 10 g of ethyl alcohol by 25°C

Answer 1

THE ANSWER IS "A", I AM 100 PERCENT SURE.

The simplest way for me to think about it is that water vapor has

more potential energy than liquid water.  This is because water

molecules attract each other, so that it requires energy to separate

them.  "Heat" is just molecular kinetic energy; higher temperature

means that the molecules have higher kinetic energies.  So when

water molecules come together, as when vapor condenses to liquid,

the potential energy decreases and kinetic energy increases, just as

a dropped ball goes faster and faster as it drops and its kinetic

energy decreases.  That means that the water molecules move faster

(more kinetic energy) when vapor condenses to liquid, meaning that

the temperature increases.  Conversely, temperature decreases when

liquid evaporates to form vapor.

This effect has profound implications for the earth's weather as

well as air conditioning systems!

check out this site for info:

http://www.newton.dep.anl.gov/askasci/ch...

email me if you have anymore questions:

[e-mail]

Answer 2

Lots of wrong answers, and no calculations.

D is the answer. heat of vaporization of water is 2.256 MJ/kg or kJ/g so 5 grams of water will give off about 11000 joules of heat.

A) specific heat of water is 4.2 J/gC

so E = is 80 x 1 x 4 = 320 J

B) E = 4 x 10 x 40 = 1600 J

C) Same as D, but only 1/5 or 2200 J

E) I have to look up...

specific heat of ethanol is about 2.5 (kJ/kg.K) or J/gC

E = 2.5 x 10 x 25 = 625 J

Answer 3

B is the answer. Largest mass and temperature change combined.