Latent Heat Problem/ Phase Change .

[jdhutto]

Latent Heat Problem/ Phase Change...Please Help!

At 1:00pm you place an ice cube tray in the freezer. Each of the 12 1-gram cubes has a temperature of 20°C. At 1:10 the water temperature has dropped to 12°C. At what time will you have ice?

i have been messing around with this problem for like 20 minutes and I am missing something, I am using Q=mc delta T, and i know it takes 1 cal/g/degree C to go from 20 down to zero, and you have to add the latent heat from water to ice to that to get Q total, i just can't figure out how to work the time factor in...please help, thanks

 

[alphysicist]

Hi jdhutto,

At 1:00pm you place an ice cube tray in the freezer. Each of the 12 1-gram cubes has a temperature of 20°C. At 1:10 the water temperature has dropped to 12°C. At what time will you have ice?

i have been messing around with this problem for like 20 minutes and I am missing something, I am using Q=mc delta T, and i know it takes 1 cal/g/degree C to go from 20 down to zero, and you have to add the latent heat from water to ice to that to get Q total, i just can't figure out how to work the time factor in...please help, thanks

I believe that they want you to assume that the rate of heat flow out of the ice is constant. Do you see what to do now?