The Solar System — Drills · Grade 9 Science

Chapter: Earth, Moon & Solar System

What these drills covers

By the end of The Solar System you should be able to:

8 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: astronomical unit (AU), terrestrial planet, gas giant, asteroid.

Problem 1

The inner planets are mainly
  1. gas giants
  2. small and rocky
  3. made of ice
  4. larger than the outer planets
Answer and explanation

small and rocky

Mercury, Venus, Earth and Mars are rocky and comparatively small.

Problem 2

How many planets are in the Solar System?
Answer and explanation

8

Eight, since Pluto was reclassified as a dwarf planet in 2006.

Problem 3

The asteroid belt lies between
  1. Earth and Mars
  2. Mars and Jupiter
  3. Jupiter and Saturn
  4. Neptune and the Sun
Answer and explanation

Mars and Jupiter

It separates the inner rocky planets from the outer giants.

Problem 4

Outer planets are gas and ice giants largely because they formed
  1. closer to the Sun
  2. beyond the line where ices could condense
  3. from asteroids
  4. after the Sun died
Answer and explanation

beyond the line where ices could condense

Beyond that distance, volatile materials could condense and accumulate into large planets.

Problem 5

Light takes about 8 minutes to reach Earth from the Sun. Roughly how many minutes to reach Mars, which is about 1.5 times as far, to the nearest minute?
Answer and explanation

12 minutes

8 × 1.5 = 12 minutes.

Problem 6

A comet's tail points
  1. behind its direction of travel always
  2. away from the Sun
  3. toward the Sun
  4. toward Earth
Answer and explanation

away from the Sun

Solar wind and radiation push the tail away from the Sun regardless of the comet's motion.

Problem 7

Explain why Pluto was reclassified and what the episode shows about scientific categories.
Answer and explanation

Pluto did not meet one of the agreed criteria for a planet: it has not cleared other objects from the neighbourhood of its orbit, sharing its region with many similar bodies. The reclassification followed the discovery of comparable objects, which made the old boundary untenable. It shows that categories are tools defined for a purpose and revised when new evidence makes the old definition unworkable, rather than facts discovered in nature.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

Explain why distances in the Solar System are given in astronomical units rather than kilometres.
Answer and explanation

The numbers in kilometres are unwieldy — hundreds of millions to billions — and hard to compare at a glance. One astronomical unit is the average Earth–Sun distance, so saying Jupiter is about 5 AU from the Sun immediately conveys that it is five times further out than Earth. The unit is chosen to make the comparisons that matter easy to see.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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