Thermal concepts questions (chem related)

[yamugushi]

I know these aren't exactly physics problems but I'm being asked them in physics so...

Homework Statement

1) As lead melts there is a change in it's...
Temperature
Heat of fusion (what I now think it is)
Avg molecular KE (what I thought it was)
Avg molecular PE

2)In a room there is 250kg of air, in the avg molecular mass of air is 28.8g/mol (.0288kg) how many particles of "air" is in the room?

Homework Equations

1) none

2) n=m/M

The Attempt at a Solution

1) look above in parentheses

2)
n=250/.028
8860.55

 

[ideasrule]

Your answers to #1 are wrong. Check your textbook for an explanation of the heat of fusion. I can explain it here, but it's too important a concept to cover thoroughly in one forum post.

For #2, you found the number of moles. The question asks for the number of actual particles.

 

[kerimek]

particles of "air" in the room

I am happy to see that you are thinking critically about these thermal concepts. It is important to understand the different factors that affect the behavior of materials, such as lead melting. I would like to provide some clarification on your answers to the questions.

1) As lead melts, there is a change in its temperature, but there is also a change in its heat of fusion. The heat of fusion is the amount of energy required to change a substance from solid to liquid at its melting point. In this case, as lead melts, it absorbs heat energy, which increases its temperature and allows it to overcome the intermolecular forces holding the solid together. The average molecular kinetic energy and potential energy also change during this process, but they are not directly related to the melting of lead.

2) Your calculation for the number of particles of "air" in the room is correct. However, it is important to note that air is a mixture of different gases, each with its own molecular mass. So, the average molecular mass of air (28.8 g/mol) may not accurately represent the molecular mass of all the gases present in the room. Additionally, the number of particles of air in the room will constantly change due to diffusion and other factors. Therefore, this calculation only provides an estimate of the number of particles at a given moment.

I hope this helps clarify these thermal concepts for you. Keep up the good work in your studies!