Achieve #9 (Week 5)

[asheagg3I]

Hi,

Can someone help with the initial steps to this question?

[Caleb_Mei_1J]

Hey there!

It is important to note that the amount of heat gained by the water that is at 25.00 degrees C will be equal to the amount of heat lost by the water that is at 90.00 degrees C. As such, you can set an equality statement -q = q such that -q refers to that of the 25.00 degree water and q refers to that of the 90.00 degree water. Doing so will help you determine the final temperature of the water when both water sample are combined.

I hope this helps!

[Meghan Spoeri 2D]

hi! you use the equation mass(cold water)(C=specific heat)DeltaT(cold water) = -mass(hot water)(C)DeltaT(hot water) and then plug in the numbers given.

[Christine Lin 1H]

Hey there!

It is important to note that the amount of heat gained by the water that is at 25.00 degrees C will be equal to the amount of heat lost by the water that is at 90.00 degrees C. As such, you can set an equality statement -q = q such that -q refers to that of the 25.00 degree water and q refers to that of the 90.00 degree water. Doing so will help you determine the final temperature of the water when both water sample are combined.

I hope this helps!

Thank you for the great explanation? Do you know if there is a specific reason why we can set q=-q for this case? Thank you in advance :)

[MaiVyDang2I]

That's because we're combining them together, so the heat lost by one will be gained by another, and q = -q for each.

[Vanessa Wiratmo 3k]

Hello,

We say q = - q because one side is losing heat, while the other is gaining heat. The heat lost will be proportional to the heat gained.

[SofiaMammaro-1K]

You use the following equation:
m(cold water)cΔT(cold water)=−m(hot water)cΔT(hot water)

[Meghan Spoeri 2D]

-q = q relates to the equation q(surroundings) + q(system) = 0. So, if the system is losing heat, then the surroundings would be gaining heat and vice versa. That is where you get the equation. q surroundings = -q system.

In this case, you have hot and cold water so as the hot water is transferred to the cold water heat is lost (-q). When the cold water mixes with the hot water, heat is gained (+q). You can set them equal because you are not losing any heat in this process, rather the heat is being transferred.