qsys=-qsurr? Winter 2013 Midterm

[Joshua Kim 3H]

I know q of sys= -q surr.

For Q2A I believe the ice is positive q while water is negative q because water is the surrounding that you put the ice in.

But for Q3A Katana question, why isn't the water that the katana is dunked into negative? I thought the katana was the system and the water is the surroundings but it has it as -q of katana?

[Kanwaldeep Rai 2H]

The negative sign just represents what thing (water or katana) releases the heat and which absorbs the heat. Because the katana has a larger temperature, heat is going to be released from the katana to the water making q negative while the water absorbs that heat making q positive. Either of them could be the system or surrounding; that's just a preference.
Hope this helped.