The Earth is a materially closed system but and energetically opened one. In other words, energy, but not matter, flows in and out.

A trip to Mars would necessitate living in a materially-closed system (a spacecraft, in this case), much as we do on Earth. What are some of the needs for life on board a spacecraft? NASA has a site that discusses "advanced life support" on long missions. Check out http://quest.arc.nasa.gov/space/challenge/background/als.html. In this article, how does NASA propose to meet some of the critical needs of life on this several year voyage?

Chemical equations involve the rearrangement of atoms. The equations summarize chemical processes, using formulas to represent the reactants and products. Chemical reactions (and everything else) obey the Law of Conservation of Mass (discounting the gain or loss of minute amounts of energy). Chemical reactions can be quite complex.

In this section (Case-in-Point), we discuss the Biosphere 2 project, a (theoretically) closed system in which flora and fauna could thrive without outside influences of any kind. Although things did not work exactly as planned, the facility is doing meaningful research. Check out the site http://www.bio2.edu/Research/rnews98s7.htm, discussing the effects of carbon dioxide on the Rainforest ecosystem. What are the conclusions of this report? Why are they important for us to know?

Aluminum production and recycling make excellent case studies for the application of stoichoimetry.

In this chapter we discuss recycling aluminum cans. However, recycling is done with other aluminum products as well. The site at http://www.autoaluminum.org/nr00.htm was developed by representatives of Alcoa Aluminum, Alcan Aluminum and the Aluminum Association. The discussion focuses on aluminum use and recycling in motor vehicles. What is aluminum used for in cars? How much is used? Is recycling aluminum, rather than using "new" aluminum an environmentally useful option? Does it save energy? Prove your conclusions.

Recycling involves all types of substances, but focuses especially on aluminum and plastics.

The Environmental Protection Agency (EPA) presents an overview of the status of recycling in every state in the U.S. Look at the site http://www.epa.gov/epaoswer/non-hw/muncpl/factbook/internet/mswf/prof.htm#top and select two states of interest to you. Write a full two page report comparing their recycling programs. Include in your discussion items such as: the strengths and weaknesses of each program; the quantities of materials recycled, and the goal of each state's program.

Recycling of materials is important and is a popular aspect of modern life and economic activity. The growth of recycling is driven by its economic benefits and concern for the environment.

Use the Internet to prove (or disprove) the second statement of the main point, above, "The growth of recycling is driven by its economic benefits and concern for the environment."

Green Chemistry means engaging in chemical processes that are as environmentally-benign as possible.

In the textbook we mention six of the 12 principles of Green Chemistry. There are many Web sites that have the other six, such as the University of Nottingham in England, http://www.nottingham.ac.uk/chemistry/student-opportunities/courses/greenprinciple.html. What are these six other principles, and what do they add to our understanding of Green Chemistry?