Calculating Heat Absorbed When Melting 15g Lead

  • Thread starter Mathys
  • Start date
  • Tags
    Heat
In summary, the conversation is about calculating the amount of heat absorbed when 15g of lead at its melting point is converted to liquid. The formula Q=(LHf)(m) is used, and the result of 367.5J is obtained. However, the given answer is about 306J, causing confusion. After further discussion, it is determined that the formula and calculations are correct and the discrepancy is due to an error in the worksheet publishers.
  • #1
Mathys
2
0
1. How much heat is absorbed when 15g of lead at its melting point are converted completely to a liquid at the same temperature?
2. (variables: Q=heat, LHf=latent heat of fusion, m=mass) Q=(LHf)(m)
3. I used the formula and I keep getting 367.5J. The answer I was given states that it is actually about 306J. I really don't understand...

Help would be gladly received
 
Physics news on Phys.org
  • #2
Your answer is correct.
I get the same value using L=24.5 kJ/kg and m=0.015kg
 
  • #3
I see...then the worksheet publishers must be in error. Thank you; I wasted a lot of time because I didn't want to get such a simple question wrong.
 

1. How do you calculate the heat absorbed when melting 15g of lead?

The heat absorbed when melting a substance can be calculated using the formula Q = m * ΔH, where Q is the heat absorbed, m is the mass of the substance, and ΔH is the enthalpy of fusion for the substance. For lead, the enthalpy of fusion is 23 kJ/mol.

2. What is the mass of lead needed to absorb a certain amount of heat?

If you know the amount of heat to be absorbed and the enthalpy of fusion for lead (23 kJ/mol), you can rearrange the formula Q = m * ΔH to solve for m. The mass of lead will be equal to the heat absorbed divided by the enthalpy of fusion.

3. How does the heat absorbed change if the mass of lead is doubled?

The heat absorbed is directly proportional to the mass of the substance. This means that if the mass of lead is doubled, the heat absorbed will also double. This relationship can be represented by the formula Q = m * ΔH, where Q and ΔH are constant and m is the mass of the substance.

4. Does the heat absorbed when melting lead change with temperature?

The heat absorbed when melting lead does not change with temperature. This is because the enthalpy of fusion for a substance is a constant value and is not affected by temperature. However, the temperature of the lead will change as it absorbs heat and melts.

5. How does the heat absorbed when melting lead compare to other substances?

The heat absorbed when melting lead is relatively high compared to other substances. This is due to lead's high enthalpy of fusion, which is influenced by its atomic structure and bonding. Other substances may have lower or higher enthalpies of fusion, leading to different amounts of heat absorbed when melting.

Similar threads

I try to solve a thermodynamics problem on heat transfer
    • Introductory Physics Homework Help
Replies
3
Views
972
The Mystery of Heat Loss: Examining Ice Melting Without Heat Loss
    • Introductory Physics Homework Help
Replies
11
Views
989
Clausius-Clapeyron equation and absorbed heat
    • Introductory Physics Homework Help
Replies
3
Views
1K
Question about thermal physics -- Ice cubes melting in water
    • Introductory Physics Homework Help
Replies
8
Views
2K
Confusion about whether to use the specific heat of water or ice
    • Introductory Physics Homework Help
Replies
4
Views
1K
How much heat in joules must be added to 0.841 kg of aluminu
    • Introductory Physics Homework Help
Replies
4
Views
3K
Thermodynamics Ice Melting Question
    • Introductory Physics Homework Help
Replies
4
Views
2K
Find the fractional increase in inertial mass when an ice cube melts
    • Introductory Physics Homework Help
Replies
10
Views
2K
What was the initial temperature of the lead bullet before it melted completely?
    • Introductory Physics Homework Help
Replies
3
Views
994
Thermodynamics: Internal Energy, Heat and Work Problem
    • Introductory Physics Homework Help
Replies
1
Views
895

Hot Threads

Recent Insights

Back
Top