Phase change

[itzeelpadillaDis1A]

How do we know when to do a phase change like on #7 on test 1?

[Kaileigh Yang 2I]

You know the phase change would occur because it's changing from a solid to a liquid. It is not only increasing in temperature, the heat required to change the physical form of the substance would need to be taken into account as well.

[Clement Ng]

Usually when temperature is constant and no chemical reaction is occurring.

[Kyra LeRoy 1E]

You'll know to do a phase change when it hits the temperature for fusion or vaporization. I think normally these questions will have to do with ice/water because the melting point is 0 degrees Celsius and boiling is 100 degrees, and so its a pretty straightforward/easy one to remember. If it is ice at 0 degrees then you know you must work with melting, and if it is liquid at 100 degrees you know you have to deal with vaporization.

[Pooja Nair 1C]

You can usually tell it's a phase change from the question either explicitly stating it or from the information given. I think these questions are usually about water, because we already know the melting/freezing point. In the case of #7, since you have a cube of ice at 0.0 Celsius, which is the freezing point, reacting with the tea/water which is at a higher temperature, you can expect melting of the ice cube, as any heat transferred to it will raise the temperature above 0 Celsius.