Which one of the following is the correct sequence of arrangement of the given planets in descending order of their density (in gm/cm³) ?
- (a)Earth > Jupiter > Venus > Saturn
- (b)Jupiter > Earth > Saturn > Venus
- (c)Earth > Venus > Jupiter > Saturn
- (d)Earth > Venus > Saturn > Jupiter
Correct — C, Earth > Venus > Jupiter > Saturn. Density falls from the rocky (terrestrial) planets to the gas giants. Earth is the densest planet in the solar system (≈5.5 g/cm³), followed by another rocky planet, Venus (≈5.2 g/cm³). The gas giants are far less dense because they are mostly hydrogen and helium: Jupiter is about 1.3 g/cm³ and Saturn about 0.7 g/cm³ — so low that Saturn would float on water. The correct descending order is therefore Earth > Venus > Jupiter > Saturn.
- (a)Earth > Jupiter > Venus > Saturn — This wrongly puts the gas giant Jupiter (≈1.3 g/cm³) above the rocky Venus (≈5.2 g/cm³). Rocky planets are much denser than gas giants, so Venus must come before Jupiter.
- (b)Jupiter > Earth > Saturn > Venus — This ranks the gas giant Jupiter above Earth, but Earth (≈5.5) is far denser than Jupiter (≈1.3). Earth is the densest of all planets, so it must come first.
- (d)Earth > Venus > Saturn > Jupiter — The first two are right, but Saturn (≈0.7 g/cm³) is the least dense planet, below Jupiter (≈1.3). Saturn should be last, not third.
A planet's mean density reflects what it is made of. The four inner terrestrial planets (Mercury, Venus, Earth, Mars) are rock and metal and are dense; the outer giants (Jupiter, Saturn, Uranus, Neptune) are mostly light gases and are far less dense. Earth is the densest planet, and Saturn is the least dense — so low it is less dense than water.
Split the list into rocky and gaseous. Rocky Earth and Venus (both ≈5 g/cm³) sit at the top; gaseous Jupiter (≈1.3) and Saturn (≈0.7) at the bottom, with Saturn last. That immediately gives Earth > Venus > Jupiter > Saturn.
- Earth has the highest mean density of any planet (≈5.51 g/cm³).
- Venus is next (≈5.24 g/cm³), being a rocky planet like Earth.
- Jupiter (≈1.33 g/cm³) and Saturn (≈0.69 g/cm³) are low-density gas giants.
- Saturn is the least dense planet — less dense than water, so it would float.
- Ranking planets by size or mass instead of density — Jupiter is largest but far less dense than Earth.
- Forgetting Saturn is the least dense planet, so low it would float on water.
A sequencing question asks planets in increasing or decreasing order of density (or size, mass, distance) — separate rocky from gaseous planets and remember Earth is densest, Saturn least dense.
Which one of the following statements is correct with reference to our solar system?
- (a) The Earth is the densest of all the planets in our solar system
- (b) The predominant element in the composition of Earth is silicon
- (c) The Sun contains 75 % of the mass of the solar system
- (d) The diameter of the Sun is 190 times that of the Earth
Answer(a) The Earth is the densest of all the planets in our solar system
States the fact that anchors this ordering — Earth is the densest planet, which is why it leads the descending-density sequence.
- practice — not a real PYQ
Which planet of the solar system has the lowest mean density?
- (a)Mercury
- (b)Earth
- (c)Saturn
- (d)Mars
Answer(c) Saturn — at about 0.7 g/cm³ it is less dense than water and the least dense planet.
- practice — not a real PYQ
Which is the densest planet in the solar system?
- (a)Jupiter
- (b)Earth
- (c)Mercury
- (d)Venus
Answer(b) Earth — its mean density (≈5.5 g/cm³) is the highest of all the planets.