High School Physics Competition: Change in Entropy

• ReneG
In summary, the question asked for the change in entropy of a system when 1.25 x 10^3 J of heat is added at a constant temperature of 75.0 C. The work shows that the change in entropy is 3.59 J/K, making answer choice c) the correct choice. The hashtag in answer choice d) appears to be a misprint and was clarified to mean "negative" by another participant.
ReneG
During a physics competition, I came across this question.
What is the change in entropy of the system when 1.25 " 103 J of heat is added to the system that is maintained at a constant 75.0 C?

My work was
\begin{align*}\Delta S &= \frac{Q}{T} \\ \Delta S &= \frac{1.25 \times 10^3 \, \mathrm{J}}{348 \, \mathrm{K}} \\ \Delta S &= 3.59 \,\,\mathrm{\left( J/K\right )} \end{align*}

but I was stuck in between two answer choices

c) + 3.59 J/K
d) # 3.59 J/K

I had no idea what the hashtag meant, so I skipped it. Can someone clear this up for me?

Honestly I have no idea, but certainly the change in entropy is positive, so answer c) is correct. Maybe it's a misprint?

I guess what dipole said it's right 'cause it sometimes happens

Last edited:
For anyone who was wondering, the hashtag just meant "negative". Thank you dipole.

I would like to clarify that the hashtag symbol (#) is not a valid mathematical or scientific notation. Therefore, option d) # 3.59 J/K is not a correct answer choice. The correct answer is c) + 3.59 J/K, as you have correctly calculated. The plus sign indicates that the change in entropy is positive, meaning that the system has become more disordered as heat was added. I hope this clears up any confusion.

1. What is the purpose of a high school physics competition focused on change in entropy?

A high school physics competition focused on change in entropy aims to test students' understanding of thermodynamics, specifically the concept of entropy and how it relates to changes in a system. It also encourages students to apply their knowledge to real-world scenarios and problem-solving.

2. How is change in entropy measured?

Change in entropy is measured in units of joules per kelvin (J/K). It is calculated by taking the heat transferred in a reversible process and dividing it by the temperature at which the transfer occurs.

3. What are some examples of systems with changes in entropy?

Examples of systems with changes in entropy include ice melting into water, gas expanding in a container, and a chemical reaction occurring. In each of these cases, there is a change in the arrangement of the particles, resulting in a change in entropy.

4. How does entropy relate to the second law of thermodynamics?

The second law of thermodynamics states that in any spontaneous process, the total entropy of the universe always increases. This means that in any natural process, the amount of energy available to do work decreases, and the disorder or randomness of the system increases.

5. What are some practical applications of understanding change in entropy?

Understanding change in entropy is important in many fields, including engineering, chemistry, and environmental science. It can help in the design of more efficient energy systems, predicting the direction of chemical reactions, and understanding the impact of human activities on the environment.

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