In this chemistry activity (on page 2 of the PDF), learners corrode a penny in a cup with vinegar, salt water, and a source of iron (nails, paper clips, or twist ties). The combination of salt and acid (vinegar) in the water helps cause the corrosion (oxidation) of iron. Iron combines with oxygen to form rust (iron oxide). If the iron is in contact with copper, the copper accelerates this reaction, and also corrodes. This is one of three activities in the Take Home guide for the Environmental Chemistry unit in OMSI's Chemistry Lab. The other two activities are Recycling Paper and Water Ways.