Grade 8 Science - Unit 5

Compared to Earth, Mercury rotates on its axis very slowly. Based on this information, what can you conclude about Mercury?

• Mercury applies weaker gravitational forces on objects.

• The length of a day on Mercury is much longer than Earth.

• Mercury has no atmosphere.

• The surface of Mercury is rocky.

Which of the following arranges the objects based on increasing weight of the 1 kg mass?

• A. Earth, Jupiter, Mars, Moon, Sun

• B. Jupiter, Sun, Moon, Earth, Mars

• C. Moon, Mars, Earth, Jupiter, Sun

• D. Sun, Jupiter, Mars, Moon, Earth

A “year” on Earth is 365.26 days long. A “year” on Saturn lasts over 29 times longer than Earth. Which of the following best explains this difference between the two planets?

• A. Saturn is farther from the Sun than Earth.

• B. Saturn rotates on its axis faster than Earth.

• C. Saturn has greater gravitational force than Earth.

• D. Saturn revolves around the Sun faster than Earth.

A new planet is discovered in a different solar system. The new planet is much like Earth. One difference is that the planet does not have seasons. What can you conclude is one feature of Earth that is lacking from the new planet?

• Earth has a tilted axis.

• Earth has a moon.

• Earth has a geosphere.

• Earth has a longer rotational period.

The diagrams below show the alignment of the Sun, the Moon, and Earth. Which diagram shows an alignment in which spring tide takes place?

• A

• B

• C

• D

In ancient times, people believed Earth was the center of the Solar System. Which of the following makes the geocentric model impossible?

• A. The moon revolves around Earth.

• B. Earth’s gravitational force is much less than the Sun’s.

• C. Orbits are elliptical, not circular.

• D. There are other planets that are closer to the Sun.

According to the diagram below, which of the following factors keeps Earth in motion around the sun?

• Speed

• Mass

• Gravity

• Friction

Why is the force of gravity between the balls in Pair 2 greater than the force of gravity between the balls in Pair 1?

• The balls in Pair 2 are closer together than the balls in Pair 1.

• The balls in Pair 2 have a greater mass than the balls in Pair 1.

• The balls in Pair 1 have more rolling friction than the balls in Pair 2.

• The balls in Pair 1 have more magnetic force than the balls in Pair 2.

Which image best represents a portion of the heliocentric model of the solar system? (S=Sun, E=Earth, and M=Moon)

• a

• b

• c

• d

Which season would be experienced in the Northern Hemisphere at this time?

• Spring

• Summer

• Winter

• Fall