Heat and phase change: latent heat

In summary, a 42kg block of ice at 0°C with an initial speed of 7.3 m/s and a final speed of 3.5m/s is sliding on a horizontal surface. The mass of the melted ice can be determined by using the equation KE lost = heat gained by ice = mass melted * latent heat of fusion. The part of the block that melts is assumed to have a very small mass and all the heat generated by kinetic friction goes into the block of ice.
  • #1
alaa410
8
0

Homework Statement



A 42kg block of ice at 0°C is sliding on a horizontal surface. the initial speed of the ice is 7.3 m/s and the final speed is 3.5m/s. Assume that the part of the block that melts has a very small mass and that all the heat generated by kinetic friction goes into the block of ice. Determine the mass of the ice the melts into water

Homework Equations



Q=mL

The Attempt at a Solution



Q=mL + (1/2v^2 final- 1/2v^2initial)?
 
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  • #2
alaa410 said:
Q=mL + (1/2v^2 final- 1/2v^2initial)?
What exactly is Q in that equation?
The right hand side is dimensionally inconsistent. It mixes energy and velocity2.
 
  • #3
q is heat gained or lost; this is the equation they used in the solution so its got to be right...
 
  • #4
except they multiply not add
 
  • #5
alaa410 said:
q is heat gained or lost; this is the equation they used in the solution so its got to be right... except they multiply not add
Not exact enough for Q, and the equation would still be nonsensical.
I suggest that the equations ought to say
KE lost = heat gained by ice = mass melted * latent heat of fusion
So now you just need an expression for the KE lost.
 

FAQ: Heat and phase change: latent heat

What is heat?

Heat is a form of energy that is transferred from one object to another due to a difference in temperature. It is the energy that causes molecules in a substance to move and vibrate, resulting in a change in temperature.

What is latent heat?

Latent heat is the amount of heat energy required to change the phase of a substance without changing its temperature. This process is known as a phase change and the energy absorbed or released during this process is called latent heat.

What are the different types of phase changes?

The different types of phase changes are melting, freezing, vaporization, condensation, sublimation, and deposition. These changes occur when a substance absorbs or releases energy, resulting in a change in its physical state.

How does latent heat affect the temperature of a substance?

During a phase change, the absorbed or released latent heat does not cause a change in temperature. Instead, it is used to break or form intermolecular bonds between particles. This means that the temperature of a substance remains constant during a phase change until the process is complete.

What factors affect the amount of latent heat required for a phase change?

The amount of latent heat required for a phase change depends on the type of substance and the specific phase change occurring. Factors such as pressure, temperature, and the properties of the substance (such as its molecular structure and intermolecular forces) can also affect the amount of latent heat needed for a phase change.

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