The hotter planet is____?

Analyze the question: It asks which planet is the hottest (the "hotter planet"). Here the key is to separate closeness to the Sun from actual surface temperature.

Explain the concept:

• Mercury is the closest planet to the Sun, so many students assume it must be the hottest.
• However, Mercury has almost no atmosphere. It cannot trap heat, so its day side reaches about 430°C, but its night side drops to about -180°C.
• Venus has a very thick atmosphere made of about 96% carbon dioxide. This causes a runaway greenhouse effect, which traps heat. Its surface stays at about 465°C day and night, making it the hottest planet in the solar system.
• Pluto (a dwarf planet) and Jupiter are far from the Sun and are extremely cold at their visible surfaces or cloud tops.

Step-by-step solution:

1. Eliminate B (Pluto): very far from the Sun, around -230°C.
2. Eliminate D (Jupiter): far from the Sun, with cloud tops around -110°C.
3. Compare Mercury and Venus: Mercury is closer, but it loses heat without an atmosphere. Venus's dense CO₂ atmosphere traps heat, giving a higher average surface temperature (~465°C).
4. Venus is the hottest.

Answer: A. Venus.

Exam tip: Remember "Venus = Very hot, because of the greenhouse effect." Closest to the Sun does not always mean hottest. The atmosphere matters too!