A query about heat capacity and specific heat capacity

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Discussion Overview

The discussion revolves around the concepts of heat capacity and specific heat capacity, exploring their definitions, dependencies on mass and material, and the implications of their units. It includes a homework-related inquiry into the calculations associated with these concepts.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants note that heat capacity depends on the mass of the object, as it takes more heat to raise the temperature of a larger mass by a given amount.
  • Others argue that specific heat capacity is a property of the material itself, requiring different amounts of energy to raise the temperature of different substances.
  • One participant questions the relationship between mass and temperature increase, suggesting that mass is the determining factor rather than temperature change.
  • Another participant clarifies that while mass remains constant, a larger mass will require more energy to achieve the same temperature increase.
  • Several posts present a series of questions aimed at calculating energy requirements based on specific heat capacity and heat capacity, prompting further exploration of these concepts.
  • There is a suggestion to derive definitions and units for heat capacity and specific heat capacity to enhance understanding.

Areas of Agreement / Disagreement

Participants express differing views on the implications of mass and material properties on heat capacity and specific heat capacity. The discussion remains unresolved, with no consensus on the interpretations of these concepts.

Contextual Notes

Participants are encouraged to clarify definitions and units, but there are unresolved aspects regarding the relationship between heat capacity, specific heat capacity, and their respective calculations.

Who May Find This Useful

Students and individuals interested in thermodynamics, specifically those studying heat transfer and related calculations in physics or engineering contexts.

ellieee
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Homework Statement:: why does heat capacity depend on the mass/size of the object when it's units is J/K , and why is specific heat capacity dependent on the material/substance when it's unit is J/kgK?
Relevant Equations:: Q=Cθ
Q=mcθ

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a) It takes 10 times more heat to heat 10 liters of water by 1 degree than it takes to heat 1 liter of water by 1 degree. Heat capacity is the amount of heat it takes to heat an object per temperature increase.

b) Different materials have different internal structure and therefore require more or less energy to raise their temperatures by a given amount. Specific heat capacity is therefore a material property that depends on the material.
 
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Orodruin said:
per temperature increase.
but the temperature of the object didn't increase though? it's the mass right?
 
ellieee said:
but the temperature of the object didn't increase though? it's the mass right?
No. The mass of each object remains the same. It is just that something of the same material that has twice the mass will take twice the energy to raise the temperature.
 
@ellieee, try working through these questions, paying attention to units at all stages. Post your answers if you still have a problem.

A metal ‘X’ has a specific heat capacity of c=1000J/(kg·K).

(Note, a change of 1K is the same as a change of 1ºC, so the unit can also be written J/(kg.ºC).

Q1. How much energy is needed to raise the temperature of 1kg of X by:
a) 1K?
b) 5K?

Q2. How much energy is needed to raise the temperature of 3kg of X by:
a) 1K?
b) 5K?

Q3. What is the heat capacity, C, of a 3kg of block of X?

Q4. Using your answer from Q3, how much energy is needed to raise the temperature of the block by:
a) 1K?
b) 5K?

Q5. Compare your answers to Q2 and Q4. Are they the same? Do you see why?
 
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Steve4Physics said:
@ellieee, try working through these questions, paying attention to units at all stages. Post your answers if you still have a problem.

A metal ‘X’ has a specific heat capacity of c=1000J/(kg·K).

(Note, a change of 1K is the same as a change of 1ºC, so the unit can also be written J/(kg.ºC).

Q1. How much energy is needed to raise the temperature of 1kg of X by:
a) 1K?
b) 5K?

Q2. How much energy is needed to raise the temperature of 3kg of X by:
a) 1K?
b) 5K?

Q3. What is the heat capacity, C, of a 3kg of block of X?

Q4. Using your answer from Q3, how much energy is needed to raise the temperature of the block by:
a) 1K?
b) 5K?

Q5. Compare your answers to Q2 and Q4. Are they the same? Do you see why?
hmm I still don't get it.. Q2 was being derived through specific heat capacity, while Q4 was being derived through heat capacity, so what point can that prove?
 
ellieee said:
hmm I still don't get it.. Q2 was being derived through specific heat capacity, while Q4 was being derived through heat capacity, so what point can that prove?
It wasn't meant to prove anything! It was meant to provide some insight to help you answer your original questions!

Here' a different approach. Can you answer these:

What is the definition of the heat capacity of an object?
From this definition, find the unit in which heat capacity is measured.

What is the definition of the specific heat capacity of a substance?
From this definition find the unit in which specific heat capacity is measured.
 
Steve4Physics said:
It wasn't meant to prove anything! It was meant to provide some insight to help you answer your original questions!

Here' a different approach. Can you answer these:

What is the definition of the heat capacity of an object?
From this definition, find the unit in which heat capacity is measured.

What is the definition of the specific heat capacity of a substance?
From this definition find the unit in which specific heat capacity is measured.
heat capacity : J/K
specific heat capacity: J/kgK or J/kg °C
 
ellieee said:
heat capacity : J/K
specific heat capacity: J/kgK or J/kg °C
You haven't given the definitions (in words). From each definition, you can work out the unit. Then you'll understand why the unit is used.
 

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