Please check my work energy required to raise temp by 10degthanks

In summary, the conversation discusses the process of using a mechanical egg beater to heat 1 L of water by 10 ºC, and determines that the mass must descend through 42.6m to provide enough work for the heating process. The calculations involve determining the amount of energy required to raise the temperature of 1kg of water by 10 ºC and using the formula for mechanical work to find the value for delta x.
  • #1
Dars
13
0

Homework Statement



You want to heat 1 L of water by 10 ºC, and so you heat it with a mechanical egg beater that is powered by a 1 kg mass on a rope over a pulley. How far does the mass have to descend to supply enough work for heating the water?

Homework Equations


|work| = mg(x_f - x_0)
C_P (liquid water) = 75.3JK^-1mol^1


The Attempt at a Solution


I first asked myself how much energy does it take to increase the temp of 1kg of water by 10degC.
Heat capacity of water (above) is the energy required to heat 1 mol of water by 1deg.
So I first determined how many moles of water i have:

1L = 1kg = 1000g * (1mol/18.01g) = 55.5mol of liquid water

Therefore 55.5mol *75.3JK^-1mol^1 = 4179.15J/K * 10K = 417915.0J

So it requires 417915.0J to raise the temp of 1kg water by 10degC.

This is the work required also because work is also in joules, --energy.

Then i used the formula for mechanical work to determine the value for delta x.

|work| = mg(x_f - x_0)

417915.0J(1kJ/10000J) = 1kg(9.81m/s/s)(x_f) (i got ride of x_0 because I set scale so that x_0 = 0)

x_f = 42.6m

So the mass has to descend through 42.6m in order to heat 1kg of liquid water by 10 degC.

Is this correct or if not please help..thanks alot. I also have some other questions about the problem but i don't want to ask until i know if my answer is correct...thank you again
 
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  • #2
Dars said:
1L = 1kg = 1000g * (1mol/18.01g) = 55.5mol of liquid water
Correct.
Dars said:
Therefore 55.5mol *75.3JK^-1mol^1 = 4179.15J/K * 10K = 417915.0J
"WORNG." Ten x four thousand equals four hundred thousand?
Dars said:
Then i used the formula for mechanical work to determine the value for delta x.
|work| = mg(x_f - x_0)
417915.0J(1kJ/10000J) = 1kg(9.81m/s/s)(x_f) (i got ride of x_0 because I set scale so that x_0 = 0)
x_f = 42.6m
So the mass has to descend through 42.6m in order to heat 1kg of liquid water by 10 degC.
"Four kilometers." You need to pay attention to decimal "orders of magnitude."
 

What is the formula for calculating the energy required to raise the temperature by 10 degrees?

The formula for calculating the energy required to raise the temperature by 10 degrees is Q = m x c x ΔT, where Q is the energy required (in Joules), m is the mass of the object (in grams), c is the specific heat capacity of the material (in J/g°C), and ΔT is the change in temperature (in °C).

What is the specific heat capacity of a material?

The specific heat capacity of a material is the amount of energy required to raise the temperature of 1 gram of the material by 1 degree Celsius. It is measured in units of J/g°C.

How does the mass of an object affect the energy required to raise its temperature?

The energy required to raise the temperature of an object by 10 degrees is directly proportional to its mass. This means that the more mass an object has, the more energy is needed to raise its temperature by 10 degrees.

What is the unit of measurement for energy required to raise the temperature by 10 degrees?

The unit of measurement for energy required to raise the temperature by 10 degrees is Joules (J).

Can the energy required to raise the temperature by 10 degrees be negative?

No, the energy required to raise the temperature by 10 degrees cannot be negative. It is always a positive value, as energy is needed to increase the temperature of an object.

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