How much heat is released from water into ice.

In summary, the total heat released when 250 g of water at 10 degrees celcius freezes into ice and cools to -10 degrees celcius is -9.86*10^4 J. This is calculated by breaking the process into three stages: cooling to freezing point, freezing, and cooling to final temperature. Each stage is governed by a different heat constant. After correcting mistakes in the calculation, the correct answer is obtained.
  • #1
ScienceGeek24
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Homework Statement


How much heat is released when 250 g of water at 10 degrees celcius freezes into ice and cools to -10 degrees celcius?

Homework Equations


Q=mcΔt

The Attempt at a Solution



q= (250g)(4186)(283-273)=1.046*10^4 J

than q=(250g)(2090)(263-283)=-1.045*10^4 J

when i subtract the two i get 1*10^4

The answer is -9.86*10^4 what am i doing wrong?
 
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  • #2
Three stages:
1. Cool to freezing point
2. Freeze
3. Cool to final temp

Each stage is governed by a different heat constant.
 
  • #3
OK this is what I'm doing

1. cool to freezing point

q=(.250kg)(4186J/kgK)(273K-283K)=-1.046*10^4J

2.Freeze

MLf=(.250)(3.33*10^5)=8.32*10^4 J

3.Cool to final temp

Q= (.250kg)(2090j/kgK)(-283K-273K)=-2.90510*10^5

so when i sum up Q1+mLf+Q2= -2.177*10^5 J
Like seriously what am i doing wrong?
 
  • #4
got it! i found the mistakes ! thanks! :D
 
  • #5


Hello,

Thank you for your question. It seems like you are on the right track with using the equation Q=mcΔt to calculate the heat released from water into ice. However, there are a few things that may be causing your calculation to differ from the expected answer.

Firstly, it is important to note that the specific heat capacity of water changes when it freezes into ice. The specific heat capacity of water is 4186 J/kg*K, but the specific heat capacity of ice is only 2090 J/kg*K. This means that the amount of heat needed to raise the temperature of water by 1 degree Celsius is different from the amount of heat needed to raise the temperature of ice by 1 degree Celsius.

Secondly, when calculating the heat released from water into ice, it is important to consider the change in temperature of the water and ice. In this case, the water starts at 10 degrees Celsius and freezes into ice at 0 degrees Celsius. However, the ice then cools from 0 degrees Celsius to -10 degrees Celsius. This means that there are two separate temperature changes to consider: 10 degrees Celsius to 0 degrees Celsius, and 0 degrees Celsius to -10 degrees Celsius.

To calculate the total heat released, you would need to use the equation Q=mcΔt for each temperature change and then add the results together. So, your calculation would look like this:

Q1= (250g)(4186)(0-10)= -1.046*10^4 J (heat released during freezing)
Q2= (250g)(2090)(-10-0)= -5.225*10^3 J (heat released during cooling)

Total heat released = Q1 + Q2 = -1.046*10^4 J + (-5.225*10^3 J) = -1.569*10^4 J = -15.69*10^3 J = -1.569*10^4 J

I hope this helps clarify the calculation for you. Keep in mind that there may be slight variations in the answer depending on the specific heat capacities used, but the overall process should be the same. Let me know if you have any further questions.
 

1. How does the amount of heat released from water turning into ice compare to the amount of heat released from ice turning into water?

The amount of heat released from water turning into ice is equal to the amount of heat released from ice turning into water, as they are opposite processes and follow the same thermodynamic principles.

2. Does the temperature of the water or ice affect the amount of heat released?

Yes, the temperature of the water or ice does affect the amount of heat released. The higher the temperature of the water, the more heat is released when it turns into ice. Similarly, the lower the temperature of the ice, the more heat is released when it turns into water.

3. What factors can affect the amount of heat released from water into ice?

The amount of heat released from water into ice can be affected by the initial temperature of the water, the amount of water and ice present, and the surrounding temperature. Additionally, the presence of impurities in the water can also affect the amount of heat released.

4. Is the amount of heat released from water into ice a constant value?

No, the amount of heat released from water into ice is not a constant value. It can vary depending on the factors mentioned above and the specific conditions of the process.

5. How is the amount of heat released from water into ice measured?

The amount of heat released from water into ice can be measured using a calorimeter, which is a device that measures the change in temperature of a substance during a phase change. This change in temperature can then be used to calculate the amount of heat released.

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