In an experiment in which molten naphtha-lene is allowed to cool…
In an experiment in which molten naphtha-lene is allowed to cool, the cooling curve in figure 7 was obtained. The temperature 80°C is known as the
A. cooling temperature
B. boiling point
C. melting point
D. vaporization point
As temperature increases from right to left, the first step is the melting point, and the second step is the boiling point.
Firstly, as heat is applied to the naphthalene, it melts at 80°c. As the heat continues, it then boils at 90°c (according to the graph at least).
Now for the right answer to the above question:
- A is not the right answer. all the temperatures can be regarded as cooling temperatures if they are reducing.
- B is incorrect. the boiling point will be the point where the naphthalene changes from liquid to gas or from gas to liquid. It is the second step on the left hand side.
- C is correct.
- D is incorrect. not vaporization point.
You may please note this/these:
- As temperature increases from right to left, the first step is the melting point.
- And the second step is the boiling point.
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/ culled from 2020 JAMB-UTME physics past question 35 /