Quantity of heat absorbed or released

In summary: The Attempt at a Solution My book said that 1 cal will raise the temp of 1g of water by 1 degree, so I used that equation to figure out the quantities of heat absorbed and released in each case.
  • #1
bjoyful
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Homework Statement



Calculate the quantity of heat absorbed (+) or released (-) during each of these changes: A. 250g. of water (about 1 cup)is heated from 15 degrees centigrade to 100 degrees; B. 500g. of water is cooled from 95 degrees centigrade to 55 degrees; C. 5.0ml. of water at 4 degrees centigrade is warmed to 44 degrees centigrade. Be sure to show all your calculation work in each case.

Homework Equations



My book gave me the formula 1.00 cal/g x C (with the degrees “dot,” – don’t know how to insert it in typing). It said that this means 1 cal will raise the temp of 1 gram of water by 1 degree. The book also gave another forumla to use 4.18J/g x C (again degrees)

The Attempt at a Solution



Which formula should I use for this question? I realized that an increase in temp = absobed heat and decrease in temp = released heat, so A and C would be absorbed heat and B released heat. Also, when the question uses centigrade, is it ok to think of it as Celsius? I read that they are pretty interchangable, but I want to make sure it isn't a "trick" question.

A. 1.00 cal / 250g x C (temp.) Is the temp the 15, 100 or the difference between the two (85).
B. 1.00 cal / 500g x C (temp) Is the temp the 95, 55 or the difference of 40?
C. Since this one is in mL, I am a little uncertain if this formula still applies as it is in grams. Or do I need to do some converting?

I am under the impression that quantity of heat thing has some thing to do with Joules. So should my answer be in Joules?:confused:
 
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  • #2
the AMOUNT OF ENERGY required to raise the temperature (or released to cool the temperature) depends on what? there are actually 3 parameters.

calories and joules are different units for energy. ignore the calories in this question, interprete it as being joules unless the answer required is to be in joules, then you need to convert cal to J.

Hint: density of water is taken as 1 g/cm3 or 1 g/ml
so, what can you deduce?
 
Last edited:
  • #3


I would recommend using the formula 4.18J/g x C, as it is the more commonly used unit for heat in scientific calculations. However, both formulas are correct and can be used interchangeably.

For A, the formula would be (100 - 15) x 250g x 4.18J/g x C = 83,500J of heat absorbed.

For B, the formula would be (55 - 95) x 500g x 4.18J/g x C = -83,500J of heat released.

For C, you can convert the mL to grams by using the density of water (1g/mL). So 5.0mL of water would be equivalent to 5.0g of water. The formula would then be (44 - 4) x 5.0g x 4.18J/g x C = 1668J of heat absorbed.

Yes, you are correct that the quantity of heat is measured in Joules. It is important to keep track of units in scientific calculations, so make sure your final answer is in Joules.
 

1. What is the definition of "quantity of heat absorbed or released"?

The quantity of heat absorbed or released refers to the amount of thermal energy transferred into or out of a system during a physical or chemical process. It is measured in joules (J) or calories (cal).

2. How is the quantity of heat absorbed or released calculated?

The quantity of heat absorbed or released can be calculated using the formula Q = m x c x ΔT, where Q is the heat energy, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature.

3. What factors affect the quantity of heat absorbed or released?

The quantity of heat absorbed or released is affected by the mass and specific heat capacity of the substance, as well as the temperature change. Other factors such as the type of substance, pressure, and phase changes can also impact the amount of heat absorbed or released.

4. How does the quantity of heat absorbed or released relate to the first law of thermodynamics?

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed. The quantity of heat absorbed or released in a system is a representation of this transfer of energy, as heat is a form of energy.

5. How is the quantity of heat absorbed or released used in practical applications?

The quantity of heat absorbed or released is used in various practical applications, such as in cooking, heating and cooling systems, and chemical reactions. It is also important in understanding and predicting weather patterns and studying the behavior of substances under different conditions.

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