Chapter 21 Test

MULTIPLE CHOICE

-Choose the correct answer by clicking on your answer choice. Only one answer is correct. (2 pts. each)

2

To which of the two main groups of planets does Earth belong?

A. the outer planets

B. the gas giants

C. the terrestrial planets

D. the interior planets

2

What tool made possible the discovery of additional planets?

A. the microscope

B. the telescope

C. the gyroscope

D. the spectroscope

2

A common method for scientists to measure distances within the solar system is to use

A. the speed of sound.

B. the English system.

C. the speed of light.

D. parallax angles.

2

What evidence suggests that Mars once had a warmer climate?

A. water in its icecaps

B. thin atmospheric pressure

C. features like dry riverbeds

D. an extinct shield volcano

2

Which terrestrial planet has a day that is over two Earth months long?

A. Mars

B. Mercury

C. Pluto

D. Venus

2

Why is Venus sometimes called Earth's twin?

A. Venus rotates in the same direction.

B. Venus's air has the same gases.

C. Venus is of similar size and density.

D. Venus was born at the same time.

2

What is one factor that makes life possible on Earth?

A. a runaway greenhouse effect

B. liquid water on its surface

C. high surface gravity

D. an irregular planetary orbit

2

What does the extra energy that Saturn gives off suggest about the planet?

A. Saturn has storms in its interior.

B. Saturn is still forming.

C. Saturn is very massive.

D. Saturn contains helium gas.

2

Why is the planet Uranus considered a gas giant?

A. because it has a rocky surface

B. because it is similar to Earth

C. because it has a deep, massive atmosphere

D. because it is larger than Mercury and Pluto

2

What is unusual about Pluto's moon Charon?

A. Its orbit is not circular.

B. It's the same size as Pluto.

C. It's more dense than Pluto.

D. It's more than half of Pluto's size.

2

What evidence supports the current theory about our moon's origin?

A. The lunar maria was formed from old lava flows.

B. Lunar rocks are similar to Earth's mantle.

C. The moon is covered with impact craters.

D. We have identified the impacting body.

2

What causes the phases of the moon?

A. the relative positions of the Earth, moon and sun

B. the tilted orbit of the moon

C. the moon's period of revolution just equals its period of rotation

D. sunlight reflecting off Earth's surface

2

What happens during a total solar eclipse?

A. The shadow of Earth falls on the moon.

B. A thin ring of the sun shows through.

C. The moon completely covers the sun.

D. The moon is about the same size as the sun.

2

Why do planets or moons with atmospheres have fewer impacts?

A. The air slows and burns up small objects.

B. Fewer objects orbit near these planets.

C. Most impacts occur in remote areas.

D. Erosion erases the features of most craters.

2

What is the main difference between an asteriod and a meteoroid?

A. the shape of their orbits

B. their density

C. the size of the body

D. their effect on Earth

2

Why are the inner planets called terrestrial planets?

A. because they are very hot

B. because they resemble Earth

C. because most are gas giants

D. because they can support life

2

What is the most useful unit for measuring distances within the solar system?

A. the light year

B. the parsec

C. the kilometer

D. the astronomical unit

2

Why do active planets generally have fewer impacts than bodies like the moon?

A. because fewer objects orbit near these planets

B. because most impacts occur in remote areas

C. because geological activity removes their effects

D. because many objects fall in the ocean

2

What is one way that gas giants differ from the terrestrial planets?

A. They are much smaller.

B. They are made of rocks and ice.

C. Their atmospheres are massive.

D. Their surfaces are hard.

2

What is the evidence that Mars once had liquid water?

A. the composition of Martian icecaps

B. fossils of sea life recovered in missions

C. the dark color of the Martian sand

D. features that resemble dry riverbeds

2

Which of the following is evidence that Pluto is not a gas giant?

A. the size of its orbit

B. its density

C. its distance from the sun

D. its closeness to the Oort cloud

2

Which of these average distances is the astronomical unit based on?

A. between Earth and the sun

B. between Earth and the moon

C. between Mercury and Pluto

D. between Pluto and the sun

2

How do gas giants differ from terrestrial planets?

A. They are much smaller.

B. They are rocky and icy.

C. They are made mostly of gases.

D. They have hard surfaces.

Use the diagram below to answer questions 24 and 25.

2

Which number represents the orbit of Venus?

A. 1

B. 2

C. 3

D. 4

2

Beyond what numbered orbit are the comets of the Kuiper belt found?

A. 6

B. 7

C. 8

D. 9

Completion

- Complete the following questions by selecting the correct word from the word bank. Misspelled words will be marked as incorrect. Some answers may be used more than once, others may not be used at all. (2 pts. each)

Word Bank