What was the original temperature of the water

[Tank08]

Can someone help me with this question?
A 35g glass thermometer reads 21.6 Degrees C before it is placed in a 135 ml of water.when the water and the thermometer come to equilibrium , the thermometer reads 39.2C what was the original temperature of the water(1ml h2o=1g h20)

 

[cristo]

Wellsi, please read the PF guidelines, particularly the bit about helping in the homework forums: https://www.physicsforums.com/showthread.php?t=5374

Complete solutions are not to be posted, and help must only be given after the poster shows his work.

 

[Wellsi]

ok sorry :(

 

[Wellsi]

was just trying to help and it was good practise for me too... cause we only did that topic not long ago... won't happen again thou

 

[Tank08]

sorry about that i did not know that either, back to the wuestion i thought the specific heat for glass was 664?i don't know if that's right can someoen check it for me.

 

[Wellsi]

there are multiple values for glass isn't there?

 

[Tank08]

well that's what I am not to sure about but i tihnk its the glass a thermometer is made of because that's what it is talking about.

 

[Wellsi]

do you know which type that is? i used the silica glass specific heat capacity

 

[quantumdude]

I've "soft deleted" the full solution provided by Wellsi. I can restore it once this has been resolved.

Tank:
sorry about that i did not know that either, back to the wuestion i thought the specific heat for glass was 664?i don't know if that's right can someoen check it for me.

Wellsi
there are multiple values for glass isn't there?

Yes, there are multiple values. But if one particular glass isn't specified, then he'll need to use the one in his book. Tank, is there a table of specific heats in your textbook? Are there example problems that use the spefcific heat of "glass"?

If not, and you need a single generic value, then I say consult our best friend HyperPhysics:


http://hyperphysics.phy-astr.gsu.edu/hbase/tables/sphtt.html

 

[Wellsi]

hey tom? were we right?

 

[Tank08]

im pretty sure you did everything right its just that my teacher told me to use the specific heat of common sustenaces chart so I am just reading the glass sp of off of their but I am pretty sure you set it up correctly because that is the way i set it up.

 

[Wellsi]

so what did the chart say as the shc of glass?

 

[Wellsi]

how did you go? end up getting it ok?

 

[Tank08]

yeah i got it man thanks for the help.buy the way what grade r u in?

 

[Wellsi]

im in my final year of high school in australia... so year 12 here :)

what was the answer

 

[Tank08]

i got 40.1

 

[Wellsi]

can tom re post the answer that i put in before?

 

[Tank08]

can i show you the way i did it?

 

[Wellsi]

sure :) there was another way that i found after i posted that one which could be quicker

 

[Tank08]

well i got the same answer just diffrent way but i guess it just matters that i got the same answer

 

[Tank08]

i used
Mass(specific heat)(delta Temp)+(MASSB)(Specific heatB)(Delta temp of B)

 

[Tank08]

what did you use?

 

[quantumdude]

i used
Mass(specific heat)(delta Temp)+(MASSB)(Specific heatB)(Delta temp of B)

You're sort of on the right track. The problem is that what you have written above is an expression, but what is called for here is an equation. After all, you can't solve an expression for an unknown.

So if you are going to add up the heat transfers for the two masses, what should they equal?