Thermodynamics question with heat gain from surroundings considered

Click For Summary
SUMMARY

The discussion revolves around calculating the latent heat of fusion of ice and the heat gained from surroundings using two methods based on a heater's power output. Method 1, which incorporates both the heater's energy and the heat gained from the surroundings, yields a latent heat value of 333 J/g and a heat gain of 16.7 J/s. Method 2, which neglects the heat from the surroundings, provides an average latent heat of 279 J/g, leading to contradictory results. The consensus is that Method 1 is the correct approach, as it accounts for all energy contributions.

PREREQUISITES
  • Understanding of latent heat of fusion
  • Basic principles of thermodynamics
  • Familiarity with energy equations in physics
  • Knowledge of power calculations (Watts) in heating systems
NEXT STEPS
  • Study the concept of latent heat in detail
  • Learn about energy conservation in thermodynamic systems
  • Explore the implications of heat transfer in phase changes
  • Investigate the effects of surrounding temperature on melting processes
USEFUL FOR

Students studying thermodynamics, physics educators, and anyone involved in heat transfer and energy calculations in scientific experiments.

FaroukYasser
Messages
62
Reaction score
3

Homework Statement


A heater with a variable power is surrounded by ice in a funnel. The heater is turned on on 70W and the ice starts melting. once the rate of dropping of droplets is constant. The mass of water falling is then calculated for 5 minutes and it is found that 0.26 g/s falls every second. The experiment is repeated for 110W for 5 minutes also and the mass is found to be 0.38 g/s, Find:

1) The latent heat of fusion of ice in J/g
2) The heat gained from the surrounding per second

Homework Equations


Energy supplied by heater + heat gained from surrounding = mass * latent heat of fusion or in symbols:
E + h = mL

The Attempt at a Solution



Okay so I am having two ideas to solve this and I am not sure which one I should choose:
Method 1:
For the first time with 70 W.
E + h = mL
(70x1) + h = 0.26L (Equation 1)

For the second time with 110 W
(110x1) + h = 0.38L (Equation 2)

Equation 2 - Equation 1
40 = 0.12L >>>> L = 333 J/g to 3s.f

subbing in L into any equation. h = 16.7 J/s (W)

Method 2
L = E/m
using the first value once. L = 70/0.26 = 269.2
using second valiue of L = 110/0.38 = 289.5
Average is 279 J/gWhich method should I use?. does method one have any flaws and if so what are they. does Method 2 have any flaws and if so what is it?

Thanks in advance :)
 
Physics news on Phys.org
Your 1st method looks right. The wording is poor. There is heat gained from the surroundings plus heat gained from the heater.
Your 2nd method ignores heat h from the surroundings so you get two contradictory answers.
 
rude man said:
Your 1st method looks right. The wording is poor. There is heat gained from the surroundings plus heat gained from the heater.
Your 2nd method ignores heat h from the surroundings so you get two contradictory answers.
Hi
Thanks for your reply :). I was wandering what you meant by "wording is poor" and if there is anything i can improve. Also in method 1, are we neglecting the heat energy that is lost from the heater to the surrounding or does the constant rate of dripping indicate that all the heat from the heater is supplied to the ice?
Thanks in advance :)
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K