Free GED Test
The only truly free online GED® test prep course available!
GED HomeAbout GED TestGED Test PreparationGED FAQGED Test Login

Home | Writing | Reading | Social Studies | Math | Science

Earth Science (and space!)

The earth is a planet that orbits a star that we call the Sun.  The Sun has nine planets orbiting around it.  From the center out they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.  The moon orbits the earth and is referred to as a satellite.  Other planets also have moons orbiting them.  There is an asteroid belt between the orbits of Mars and Jupiter.  There are also comets that make long orbits that take them close to the sun and then far away again. Together, all these objects make up the Solar System, the earth’s local neighborhood. In sum, the solar system includes the sun, nine planets and their moons, asteroids, comets, meteoroids, interplanetary dust and plasma.

The Sun is one of several hundreds of billions of stars in the Milky Way galaxy. The Milky Way is the neighborhood that the Sun belongs to.  Many of the other stars have planetary systems orbiting around them.

The Milky Way is only one of the many, many galaxies sprinkled throughout the universe.

When you look with a powerful enough telescope, the galaxies appear to be moving away from each other which leads to the conclusion that the universe is expanding.


 1. Galaxies are groups or systems of:

     A. planets

     B. meteoroids

     C. stars

     D. moons

Answer: C


The Big Bang theory is used to describe how the entire universe is likely to have begun.  Physicists theorize that if we (conceptually) go back far enough in time, we find the universe starting out at a single point of very high energy and pressure. It would be hard for us to recognize or even grasp how that looked.

It went through a series of expansions and evolutions where the substance of the universe literally cooled down and formed what we see around us today.

This model has been put together by using many clues such as current expansion, various forms of  radiation that occur throughout space, and the re-creation of the original high-energy conditions in laboratories.


As the universe flung out its substance, atoms that took the form of hot gas and dust, this material started to stick to itself and form clumps much like soap bubbles do. One or more of these clumps formed the beginnings of the Milky Way and smaller ones formed the stars within it.  Our Solar System was a ball of gas and dust that coalesced under the force of its own gravity to form the sun and planets.

The Earth, like all the other planets, took time to develop into the state that it is in now.  It had a process of hardening from a molten state over long periods of time. 


1. The earth is a:

     A. Moon

     B. Star

     C. Asteroid

     D. Planet

     E. Galaxy

Answer: D

Scientists can read the history of development of the earth by examining the geologic record.  By digging into the earth, layers are uncovered revealing chemical compositions and other conditions of the past.  Fossils imbedded in these layers reveal the different forms of life that existed in the past.


More commonly just called air; the earth’s atmosphere is relatively thick and made up of nitrogen (78%), oxygen (21%) and argon (1%) as well as trace amounts of carbon dioxide and water vapor. The troposphere is the name of the lowest portion of the atmosphere, where we can see clouds. The atmosphere plays the role of buffer between the earth and the sun. The earth has an unstable atmospheric composition which is maintained by the biosphere, that is, the atmospheric oxygen sustained through the interaction of solar energy with the earth’s plants.

Read the following passage, study the diagram, and answer the questions below:

The Water Cycle:

The water cycle, also called the “hydrologic cycle,” is the process of circulation of water within the earth’s hydrosphere. It involves the change in the physical state of water between its liquid, solid and gas phases. This cycle refers to the continuing exchange of water between land, atmosphere, surface and subsurface waters and organisms. This cycle involves five main physical actions: evaporation, precipitation, infiltration, runoff, and subsurface flow.

1. Evaporation: involves the transfer of water from bodies of surface water into the atmosphere necessitating a change in the physical nature of water from liquid to gas. 90% of atmospheric water comes from evaporation.

2. Precipitation: is the atmospheric moisture already condensed into clouds and falling to the surface of the earth. Precipitation normally occurs in the form of rain, and sometimes snow, hail, and fog.

3. Infiltration: The transition from surface water to groundwater is called infiltration. Groundwater tends to be slow moving, so this water may return as surface water thousands of years later.

4. Runoff: is the name for the different ways in which land surface water moves downhill to the oceans. Streams and rivers often end in lakes for some time and don’t make it to the ocean. A lot of runoff will evaporate before reaching a body of water or an aquifer.

5. Subsurface flow: is the term for the movement of water within the earth in the vadose zone or in aquifers. After infiltration, subsurface water often returns to the surface or seeps into the ocean.

Question 1

1. In terms of the water cycle, what is the name for the process in which water that melts off of a snow cap reaches the ocean?

     A. Subsurface flow

     B. Infiltration

     C. Evaporation

     D. Precipitation

     E. Runoff

Answer: E. A snowcap is above ground and we just learned that water that melts or simply runs on the surface of the earth to an ocean is called runoff. 

Question 2

2. Which of the five physical actions involves water changing into its gaseous state? 

     A Runoff         

     B. Evaporation

     C. Precipitation

     D. Infiltration

     E. Subsurface flow

Answer: B. Evaporation is the physical process in which water changes from its liquid state into its gaseous state and is dispersed in the atmosphere.


Conservation of earth’s resources involves the protection and smart management of the natural resources supplied by the earth for the benefit of each and every person and every living organism on this planet. Without conservation, all of the natural resources that are necessary for supporting life, like air, water, minerals, soil, animals, and energy will be destroyed. Currently, we waste incomprehensible amounts of natural resources every day through conscious recklessness as well as through negligence and ignorance. If we do more to conserve, we will save money and our environment. The more the earth’s populations increase, the greater a demand there is on the earth’s limited resources, which increases the need for conservation and the search for alternative energy sources.

Read the following passage and answer the questions below:

Different Forms of Energy

Currently, the majority of our energy comes from non-renewable energy sources that can never be replaced once they are exhausted. About 90% of our energy comes from fossil fuels like crude oil, natural gas, and coal. Because of this incredible rate of use and the impending loss of all of our natural resources, many scientists and activists have turned towards alternate forms of energy. These include methanol, ethanol, garbage and plant material, corn, wind energy, solar energy, hydroelectricity, and tidal energy. These are called renewable energy sources.

Question 1

1. Why are people looking for renewable energy sources?

     A. Because they’re hippies

     B. Because we will soon be out of non-renewable energy sources

     C. Because they’re bored

     D. Because they want to increase our energy use

     E. None of the above

Answer: B

Question 2

2. Crude oil, natural gas, and coal are called

     A. Nuclear energy sources

     B. Alternate energy sources

     C. Renewable energy sources

     D. Fossil fuel sources

Answer: D

Click on the link below to move on to the Summary.

Back: Lesson 2 | Next: Science Summary

Signup! It's Free! | Language Arts | Reading | Social Studies | Math | Science

Free GED Course Online

The entire course is free and online. Nothing to pay, ever.

Click here to get started!
  Home  |  ResourcesPrivacy Policy
© Copyright 2012