In the following chart, the horizontal line is time and vertical line is temperature. $K$ and $L$ are solid matters that are placed in two identical pots within the same room and are being heated up with identical heaters.

enter image description here

(Translation: Sıcaklık = temperature, Zaman = time, dak (dakika) = minute, maddesi = substance)

Which ones of the following are true?

A-) If $K$ and $L$ are different matters, they have the same mass.

B-) If masses of $K$ and $L$ are different, they can be the same matter.

C-) If masses of $K$ and $L$ are equal, they are different matters.

I chose "only $B$" which turned out to be wrong while the correct answer is "$B$ and $C$" and in the explanation it said "You picked the wrong answer because you think different matters can't have the same boiling/melting point." which is true because they can't, right?

  • $\begingroup$ In B) and C), I assume that one of the "matter"s should be "mass". Different matters can have the same boiling and melting points. It's not a unique characteristic and was used for identification in the past only because of its simple determination. $\endgroup$ – TAR86 Jan 20 '17 at 16:06
  • $\begingroup$ Your book refers to: substance A always has boiling point P, otherwise, it is not A. Substance B always has boiling point Q. P can equal Q, however. $\endgroup$ – TAR86 Jan 20 '17 at 16:13

A is not true - no such connection exists. B is true (and given the same temperature indicating the phase transition it is in fact likely that K and L are the same matter). C is true and can be explained as follows: if K and L have the same mass, they must have different specific heat capacities, defined as:

$$ c = \frac{\text{the amount of energy to be added to raise the temperature by 1°C}}{\text{mass}} $$

This is a property that is unique for each matter - same as the melting and boiling point. It can be said to be a function of the matter. Note that the $T(t)$ graphs appear to start at the same temperature, but it takes longer to heat L than K to 85°C although the same heating is applied.

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  • $\begingroup$ Maybe it is badly translated, I dunno. It can be water - true. If boiling point is not 100°C, it cannot be water - true. $\endgroup$ – TAR86 Jan 20 '17 at 17:37

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