Heat curve problem 1 in page 10 of workbook

Moderators: Chem_Mod, Chem_Admin

204635822
Posts: 25
Joined: Fri Sep 25, 2015 3:00 am

Heat curve problem 1 in page 10 of workbook

Postby 204635822 » Thu Jan 28, 2016 4:09 pm

Isnt the heat capacity of a liquid greater than that of a solid? SO shouldnt the answet to #1 on pg 10 of workbook supposed to be B?

Chem_Mod
Posts: 17677
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 404 times

Re: Heat curve problem 1 in page 10 of workbook

Postby Chem_Mod » Fri Jan 29, 2016 6:46 am

Hi can you post the question in full so that we can help you?

Anthony Rosas 2K
Posts: 14
Joined: Fri Sep 25, 2015 3:00 am

Re: Heat curve problem 1 in page 10 of workbook

Postby Anthony Rosas 2K » Fri Jan 29, 2016 9:39 pm

You're thinking about trends you've seen. Maybe that's the case usually, maybe not, but you cannot generalize. Look at the actual heating curve given in the question.

Heat capacity is the energy required to raise the temperature of any substance by 1 degree C, or whatever the units of temperature you'd like to use. The greater the heat capacity, the less of an affect or change in temperature there will be on the substance. Look at the curve again. The slope of the solid is smaller (not as steep of a rise) than the slope of the liquid which is much steeper. As you increase heat in kJ/mol (read the curve from left to right), the slope of the liquid rising much more quickly shows that it is more affected by the change in heat, therefore has a smaller heat capacity than the solid. So this answer is true.

The same goes for the next answer choice. The slope of the gas is much steeper, therefore has a smaller heat capacity, than the slope of the liquid. Basically, the greater the heat capacity, the less of an affect a temperature change has on a substance, hence the more horizontal and less steep of a slope and vice versa. I hope this helps.

DrewGomberg_1D
Posts: 10
Joined: Fri Sep 26, 2014 2:02 pm

Re: Heat curve problem 1 in page 10 of workbook

Postby DrewGomberg_1D » Sun Jan 31, 2016 6:05 pm

I struggled with the idea of which heat capacity / phase change involved greater heat to raise in temperature per mole as well. I believe the easier way to think about it is that the higher the slope of the line is the more temperature increase you get per mole with a given amount of heat added. So the higher the slop the lower the standard heat capacities should be because you essentially get more temperature increase with the allotted amount of energy.

Chem_Mod
Posts: 17677
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 404 times

Re: Heat curve problem 1 in page 10 of workbook

Postby Chem_Mod » Mon Feb 01, 2016 12:48 am

Your method of thinking about the slope is right. Well done!


Return to “Phase Changes & Related Calculations”

Who is online

Users browsing this forum: No registered users and 0 guests