Science 9 · Unit 6: Sound and space · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. In the early twentieth century, how did scientists think the Moon was formed?

   • from a cloud of dust and gas left over after the Sun formed
   • by splitting away from the Earth, soon after the Earth was formed
   • by a collision between the Earth and a planet the size of Mars
   • by being captured by the Earth's gravity
   Check

2. 2. Measurements show the Moon is still moving away from the Earth. About how fast?

   • about 4 cm each year
   • about 4 mm each century
   • about 4 km each year
   • about 4 m each day
   Check

3. 3. Which of these is evidence that supports the collision theory?

   • The surface of the Earth does not appear to have ever been molten.
   • The Moon is bigger than the Earth.
   • The Moon has a small iron core, similar to the Earth.
   • Venus has no moon.
   Check

4. 4. Samples of rock from the Moon show that its surface was once molten. How does this fit the collision theory?

   • It contradicts it, because the Moon must have formed from the Sun.
   • It contradicts it, because a collision would have frozen the rock.
   • It has nothing to do with the theory.
   • It supports it, because a giant collision would have melted the rock.
   Check

5. 5. Which of these is evidence that contradicts the collision theory?

   • There is evidence outside the Solar System of similar collisions.
   • The Moon has a small iron core, similar to the Earth.
   • The surface of the Earth does not appear to have ever been molten.
   • The Moon is less dense than the Earth.
   Check

6. 6. Which of these statements could explain why the composition of rocks on the Earth and the Moon is very similar?

   • The Earth is mostly formed from Theia's rocks and the Moon only has a small quantity of Theia's rocks.
   • Rocks from Theia and Earth were completely mixed during the collision.
   • The Moon was captured by the Earth's gravity.
   • The Moon is mostly formed from Theia's rocks and the Earth only has a small quantity of Theia's rocks.
   Check

7. 7. Mars has two moons, Phobos and Deimos. If they were originally asteroids captured by Mars's gravity, how would their rocks compare with the rocks on Mars?

   • They would be different from the rocks on Mars.
   • They would be the same as the rocks on Mars.
   • They would be the same as the rocks on Earth.
   • They would be made of ice only.
   Check

8. 8. What is the correct order of the collision theory?

   • impact → Moon → ring of rocks and dust → Mars-sized object approaches
   • Mars-sized object approaches → impact → ring of rocks and dust → rocks and dust come together to form the Moon
   • Moon → impact → ring of rocks and dust → Mars-sized object approaches
   • ring of rocks and dust → impact → Moon → Mars-sized object approaches
   Check

9. 9. In the collision theory, what collided with the young Earth?

   • a newly formed planet about the size of Mars
   • an asteroid
   • a newly formed star
   • a comet from outside the Solar System
   Check

10. 10. If the collision theory is correct, which would contain particles from Theia?

    • both the Earth and the Moon
    • the Moon only
    • the Earth only
    • neither
    Check

11. 11. What was the name of the object that collided with Earth?

    • Luna
    • Mars
    • Venus
    • Theia
    Check

12. 12. According to the collision theory, when did the Moon form?

    • before the Sun formed
    • early in the history of the Solar System, about 4.5 billion years ago
    • at the present day
    • about 1 million years ago
    Check

13. 13. Which evidence supports the collision theory?

    • The Moon has a very large iron core.
    • The Moon is made of ice.
    • The Moon is bigger than the Earth.
    • Moon rocks are very similar in composition to Earth's rocks.
    Check

14. 14. Which fact is evidence AGAINST the collision theory?

    • Moon rocks are similar to Earth rocks.
    • Venus has no moon, though collisions were common in the early Solar System.
    • The Moon is moving away from the Earth.
    • The Moon has a small iron core.
    Check

15. 15. The fission theory says the Earth and Moon were once one object that split. Which evidence supports both the fission and collision theories?

    • The composition of rocks on the Moon is very similar to that on Earth.
    • The Moon is smaller than the Earth.
    • The Earth has one moon and some planets have more.
    • The moons of Mars were originally asteroids.
    Check