How Do You Calculate the Change in Entropy When Ice Melts in Water?

In summary: Lf = 27g * 80cal/g = 2160 calNow, to find the change in entropy, we can plug in the values into the formula:ΔS = ∫ dQrev/T = 2160 cal / 293.15 K = 7.37 cal/KIn summary, the change in entropy when 27 grams of ice at 0 oC is added to 250 grams of water at 23 oC is 7.37 cal/K or 0.78 cal/oC. This is found by calculating the amount of heat required to melt the ice and using the formula for change in entropy.
  • #1
devil0150
3
0
In 250gr water at 23 oC(degrees celsius) we throw in 27gr ice at 0 oC. Find the change in entropy.
(sorry if that was a bad translation but English is not my native language)
The answer is 0.78 calories/oC. But I'm not sure how do this. The formula I have for entropy is: S=δQ/T

I find the final temperature like this: (q lost in water = q gained in ice)
m1 * 4.184 * (23 - ft) = m2 * 4.184 * (ft - 0)
ft = 20.75 oC

Now how do I find δQ?
 
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  • #2
devil0150 said:
In 250gr water at 23 oC(degrees celsius) we throw in 27gr ice at 0 oC. Find the change in entropy.
(sorry if that was a bad translation but English is not my native language)
The answer is 0.78 calories/oC. But I'm not sure how do this. The formula I have for entropy is: S=δQ/T

The formula for change in entropy between two states is: dS = dQrev/T or ΔS = ∫ dQrev/T

where dQrev is the heat flow over a reversible path between those states.

I find the final temperature like this: (q lost in water = q gained in ice)
m1 * 4.184 * (23 - ft) = m2 * 4.184 * (ft - 0)
ft = 20.75 oC

Now how do I find δQ?
Before you can raise the temperature of the ice, you first have to melt it. What is the heat required to melt 27 g of ice?

AM
 

Related to How Do You Calculate the Change in Entropy When Ice Melts in Water?

1. What is entropy and how is it related to change?

Entropy is a measure of the disorder or randomness in a system. A change in entropy refers to the difference in the level of disorder between two states of a system. As a system evolves, it tends to move towards a more disordered state, resulting in an increase in entropy.

2. Why is it important to find change in entropy?

Finding change in entropy is important because it helps us understand the direction and extent of a process or reaction. It also provides information about the efficiency and reversibility of a system. In many cases, the change in entropy can determine whether a process is spontaneous or not.

3. How do we calculate change in entropy?

The change in entropy (ΔS) can be calculated using the equation ΔS = Sfinal - Sinitial, where Sfinal and Sinitial represent the entropy of the system in its final and initial states, respectively. This can be determined using thermodynamic properties such as temperature, pressure, and volume.

4. What factors affect change in entropy?

The main factors that affect change in entropy are temperature, pressure, and volume. Generally, an increase in temperature or volume leads to an increase in entropy, while an increase in pressure results in a decrease in entropy. Additionally, the number of particles and the complexity of the system can also influence the change in entropy.

5. Can we reverse a change in entropy?

In theory, it is possible to reverse a change in entropy, but it would require an input of energy from an external source. The second law of thermodynamics states that the total entropy of a closed system always increases with time, so reversing a change in entropy is not a spontaneous process and would require work to be done on the system.

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