Investigating Specific Heat Capacity with Boiling & Warm Water

[pdot]

I am doing a lab about specific heat. i have a cup of boiling water which i put 5 metals into, and a cup of warm water which sits at 22 degrees celcius. i am to record the difference in temperature as i am using the equation Q = mc (delta) T for part one, and then i am using the equation C = Q/m (delta ) t for part two.

For the first equation i will be using the mass of .059kg ( weight of Lead ), 4180 J/ kg degrees celcius ( i put all the metals into a boiling cup of water ) and the change of water tempterature which started at 22 degrees and went to 23 when i put the lead into the cup of water.

Q = mc (delta) t.
Q = (.059)(4180)(22-23)
please correct if i have made a mistake.
Q = -246

for the second equation i am using -246 for Q. .059kg for mass and (23-100) for change of temperature.

C = Q/m (delta ) t.
C = (-246)(.059)(23-100)
C = (-14.514)(-77) = 1117 J/KG degrees celcius. to me this is not right, and i had a substitute on friday so i couldn't ask. i also got another answer for the second equation which was 54 J/kg degrees celcius.
could someone please tell me what I am doing wrong.
Preston.

 

[rock.freak667]

For one, you said you put in all the pieces of lead into the cup, did each piece have a mass of 0.059 kg or did all in total have 0.059 kg?

Secondly, to use Q=mcΔT for the first part, you measured the final temperature of the water as 23°C after putting lead at 100°C in the water. Usually the final temperature of the water would not be that low.

In that same equation, the 'm' would be the mass of the water, you used the mass of the lead.


I think you main problem lies in the fact that you recorded the final temperature of the water ( and hence lead incorrectly). I based this solely on the fact that you put 100°C lead into 22°C water and only saw a temperature rise of 23°C.

 

[gneill]

Q = mc (delta) t.
Q = (.059)(4180)(22-23)
please correct if i have made a mistake.
Q = -246

Why are you using the mass of lead with the specific heat of water? Did you measure the volume or mass of water? "A cup" is probably not the volume, since you're most likely working with metric units...

Also, you haven't exactly explained the procedure in a clear fashion. Was the idea of putting the lead into boiling water to raise its temperature to a known starting value (100C) before dropping it into the lukewarm water?

 

[pdot]

Ok thanks guys, and i am sorry if i have not fully explained. i guess i should pay more attention in class. and i will work on explaining myself more on posts to come.

 

[pdot]

yes rock freak, my equation is not supposed to be perfect it is supposed to come close the the specific heat. i got 136, the answer in the book is 130. thank you guys again

 

[pdot]

for lead ^