Latent Heat Q: How to Lower Temp of 125 g Water to 12°C

  • Thread starter Thread starter veronicak5678
  • Start date Start date
  • Tags Tags
    Heat Latent heat
AI Thread Summary
To lower the temperature of 125 g of water from 23°C to 12°C, the energy required is calculated as -5760 J. This energy must be balanced by the heat absorbed from the melting ice, which has a latent heat of 3.34 x 10^5 J/kg. The initial calculation suggests that 17.2 g of ice is needed, but the correct answer is actually 15 g. The discrepancy arises because the melting ice will become water and mix with the existing water, which must be accounted for in the calculations. Proper consideration of the mixing process is essential for accurate results.
veronicak5678
Messages
143
Reaction score
0

Homework Statement



A well insulated cup contains 125 g of water at 23 degrees. How many grams of ice must be added to lower temp to 12?

Homework Equations



Q = c*m*delta t

The Attempt at a Solution



energy needed to lower temp:
Q = 4190 J / kg * (-11 degrees) * (.125 kg) = -5760 J

Q from ice = - Q from water = 5760 J

to find mass of ice needed:

5760 J = Latent heat of ice * mass needed = (3.34 * 10^5 J / kg) * m

= .0172 kg = 17.2 g

The correct answer is 15 g. What am I doing wrong?
 
Physics news on Phys.org
Hi veronicak5678! :smile:
veronicak5678 said:
A well insulated cup contains 125 g of water at 23 degrees. How many grams of ice must be added to lower temp to 12?
…
The correct answer is 15 g. What am I doing wrong?

hmm … you didn't stir! :wink:
 
I'm sorry, but I don't follow...
Should I be using something other than latent heat?
 
yes … the ice will become water, and mix with the water already there :smile:
 

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »
Thread 'Voltmeter readings for this circuit with switches'

Thread 'Voltmeter readings for this circuit with switches'

TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
View full post »

Similar threads

I try to solve a thermodynamics problem on heat transfer
Replies
3
Views
2K
Latent heat and specific heat in insulated container
Replies
1
Views
2K
Thermodynamics adding ice to water problem with latent heat
Replies
1
Views
3K
How many kg of ice must be dropped to make Tf= 22.7C?
Replies
9
Views
2K
Heat of Evaporation: Melting Ice to Boil Nitrogen
Replies
3
Views
2K
Quantity of heat, phase change of ice to water
Replies
7
Views
3K
Heat Capacity and Latent Heat question
Replies
3
Views
2K
Confusion about whether to use the specific heat of water or ice
Replies
4
Views
2K
How much ice to cool down this water?
Replies
17
Views
5K
Question about Phase Change & Latent Heat
Replies
13
Views
3K

Hot Threads

Recent Insights

Back
Top