Phase Change Problems: How to Solve for Heat Release and Temperature Changes

In summary, the conversation is about a student seeking help with three questions related to heat and temperature. The equations used for solving the questions are mentioned and the student is instructed to plug in the given numbers to find the final temperature.
  • #1

Homework Statement

I have three questions I need help on. Can someone please explain to me how to do them, how to correctly set up the problem, and what I need to know. I have a test tomorrow. Thanks!

Q1: How much heat is released freezing 75 grams of steam at 110 degrees C into ice at -5.1 degrees C

Q2: How much heat is released in condensing 43 grams of steam at 100 degrees C and then cooling the water to 20 degrees C.

Q3: I make a cup of tea with 43 g of water at 99 degrees C. To cool it, I add 5.1g of ice at 0 degrees C. By how much will the temperature of the tea come down by once I add the ice? (Treat tea the same as regular water)

Homework Equations

Change in Heat= mass*specific heat*change in temperature
Change in Heat=mass*latent heat

The Attempt at a Solution

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  • #2
Q1 is straight forward. Just use the first equation you posted.

[tex] \Delta Heat = m (Cp) ( \Delta Temp) [/tex]

Cp is specific to the material and you can look it up for homework and will most likely be provided for tests.

Q2 is the same as Q1. Let me know if you don't understand the first two. It should just be plugging in numbers for each variable with change in temperature equal to final temp minus the starting temp.

Q3 I don't remember.

What is a "Phase Change Problem"?

A phase change problem refers to a situation in which a substance undergoes a change in its physical state, such as from solid to liquid or liquid to gas, due to a change in temperature or pressure.

What are the different types of phase changes?

The most common types of phase changes are melting, freezing, evaporation, condensation, sublimation, and deposition. These changes can occur between the three states of matter - solid, liquid, and gas.

How does energy play a role in phase changes?

During a phase change, energy is either absorbed or released. This energy, known as latent heat, is required to break or form the intermolecular bonds between particles in a substance. For example, during melting, energy is absorbed to break the bonds between solid particles and convert them into liquid particles.

What factors influence the rate of a phase change?

The rate of a phase change is influenced by a few key factors, including temperature, pressure, and the specific properties of the substance, such as its melting point or boiling point. Generally, higher temperatures and lower pressures result in faster phase changes.

Can phase changes be reversed?

Yes, phase changes can be reversed through the application or removal of energy. For example, water can be frozen into ice by lowering its temperature, and then melted back into liquid water by increasing its temperature. However, some substances may undergo irreversible phase changes, such as burning or decomposition.

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