Calculate the Change in entropy of the universe

In summary, we are tasked with calculating the changes in entropy of the universe for a copper block of mass 0.5kg being dropped into a lake of 10 degrees while the block has a thermal capacity of 2J/K and a temperature of 100 degrees. The relevant equation is dS = dQ / T and there is confusion on whether to use dQ = mcdT or dQ = C(t). Using dQ = mcdT yields an answer of 0.5J/K, while using dQ = C(t) gives an answer of 0.1J/K. The correct answer is not clear.
  • #1
matt_crouch
161
1

Homework Statement



Calculate the changes in the entropy of the universe for

a) A copper block of mass 0.5kg is dropped into a lake of 10 degrees with the block having a thermal capicity of 2J/K and a temperature of 100 degrees

Homework Equations



dS=dQ/T


The Attempt at a Solution



ok so I know how to do the question but i am confused on 1 thing;

do i integrate dS=mcdT/T so dQ=mcdT or do i use just dQ=C(t) because it gives me the thermal capacity not the specific heat.
 
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  • #2
if i use dQ=C(t) then i get the answer 0.1J/K but if i use dQ=mcdT then i get 0.5J/K. Which one is the correct answer?
 

Related to Calculate the Change in entropy of the universe

1. What is entropy and why is it important?

Entropy is a measure of the disorder or randomness in a system. It is important because it helps us understand the direction and efficiency of energy transfer and chemical reactions in the universe.

2. How do you calculate the change in entropy of the universe?

The change in entropy of the universe can be calculated using the equation ΔS = ΔSsystem + ΔSsurroundings, where ΔSsystem is the change in entropy of the system (e.g. a chemical reaction) and ΔSsurroundings is the change in entropy of the surroundings (e.g. the environment).

3. What factors affect the change in entropy of the universe?

The change in entropy of the universe is affected by the temperature, pressure, and composition of the system and surroundings. It is also influenced by the direction and type of energy transfer (e.g. heat or work) and the spontaneity of the reaction.

4. Can the change in entropy of the universe be negative?

Yes, the change in entropy of the universe can be negative. This usually occurs when the increase in entropy of the surroundings is greater than the decrease in entropy of the system, resulting in a net decrease in entropy for the universe.

5. How does the change in entropy of the universe relate to the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of the universe always increases in a spontaneous process. Therefore, the change in entropy of the universe is a measure of the spontaneity of a reaction and its conformity to this fundamental law of thermodynamics.

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