Question

***Are negative Joules a thing?!?***

Find the amount of heat energy needed to convert 150 grams of ice at -15°C to ice at -63°C.
Select one:
a. 14760 Joules because the ice is cooling.
b. (-) 14760 Joules because the ice is cooling.
c. (-) 14760 Joules because the ice is being heated.
d. 14760 Joules because the ice is being heated.

We've never dealt with converting ice to... well, ice before, so i'm guessing the ice would cool since we're transitioning from -15°C to -63°C.

The energy needed to convert is 14760 Joules, but I've never heard of - Joules. How can energy be -?

Answer 1

the signs +/- only implicate the direction of heat transfer.

negative implies loss from the system to the surroundings
positive implies gain by system from surroundings

Answer 2

i.e. the process of cooling is an exothermic process

Answer 3

Aha. Since we're diving deeper into Celsius we'd choose B.), ja?

Answer 4

jaaa