Final answer:
Mercury is not the hottest planet despite being closest to the Sun due to its lack of an atmosphere to retain heat. Venus, with its dense atmosphere causing a greenhouse effect, holds the title of hottest planet in the solar system.
Step-by-step explanation:
It is false that Mercury is the hottest planet because it is the closest to the Sun. Although Mercury does experience extreme temperatures on its sunlit side, ranging from 280-430 °C, it does not have the highest temperatures in the solar system. The reason is that Mercury has no atmosphere to retain heat.
As a result, when the Sun sets on Mercury, the temperature can quickly drop to about -170 °C due to rapid heat loss to space. Instead, the hottest planet in our solar system is Venus, with surface temperatures around 465 °C, due to its thick atmosphere that causes a runaway greenhouse effect, trapping solar heat.