Measure the rate of rusting for different types of solid wire in water. Cut three pieces each of steel, zinc-coated steel, copper and aluminum wire. Have the students wrap one end of each wire around a pencil and then place the pencil across the mouth of a jar with the wire dangling into a jar. Repeat for two other jars. One jar should have no water, one should be full of water, and one should be full of saltwater. Observe the wires every day for two weeks and rate the wires from least rusty to most rusty. Take photos at the start and the end of each week. Discuss which wire rusted the most.
Repeat the above experiment, but this time weigh each wire before putting it into the jar. Have the students mark the weight in their notebooks. Ask the students to predict if and how the wires' weights will change. At the end of the two weeks dry the wires and weigh them again. Decide which wire's weight changed the most. Did the weight change as the students thought it would? Explain the weight change by talking about the weights of oxygen and hydrogen.
Select two metals and run the same experiment as described above, only this time dissolve 1 tbsp. of salt in one jar and leave the other jar with plain water. Take a photo and weigh the wires at the beginning and the end of the experiment. Scrape the rust off the wires and weigh them again. Which wire's weight changed the most? Explain that some metals form a protective layer when they oxidize, slowing further oxidation. Iron doesn't form that protective layer and will continue to rust.
To discover if temperature affects the speed that the wires corrode, select several different metal wires and cut them to the same size. You want them to fit inside your jars. Cut two of each metal. Record the weight of each piece before placing it in the jar. Fill the jars with saltwater and put the lid on. Place one set of jars on top of your refrigerator or water heater where it's warmer. Place the other set inside the refrigerator. Check the temperature once a day. Weigh them again at the end, before and after rubbing off any corrosion. Record the information. Is there a difference seen between the cold and warm metals?