4. The chart shows melting and boiling points of different substances.

Melting and Boiling Points

Substance

Alcohol

Formaldehyde

Nicotine

Benzene

Nitroglycerine

Melting Point ("C) Boiling Point ("C)

-114

78.2

-92

-19

-79

247

5.5

80

13.5

250

Which substance freezes at the lowest

temperature?

A. Alcohol

B. Nicotine

C. Formaldehyde

The correct option is A

Explanation:

Firstly, it should be noted that the freezing point of a substance can be assumed to be melting point of that substance because a substance will normally change from liquid to solid (freezes) at the same point it changes from solid to liquid (melts). For example, water freezes at 0°C and also starts melting at 0°C.

Thus, the substance with the lowest melting point among the substances mentioned in the question is alcohol (ethanol) with the melting point of -114°C. Hence, ethanol also has the lowest freezing point thereby freezing at the lowest temperature.

the area between the graph and the t axis

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.