Show the students the chemistry of cleansing pennies to make them look shiny and new. Get your students to line up four identical glass beakers next to one another and add 50ml of four different liquids: tap water, distilled water, pure vinegar (acetic acid) and cola. Instruct students to submerge a dirty penny into each liquid and leave it for one minute. Have students then strain away the liquids from each container before observing the pennies. Educate them about the impact of acids on the cleansing of pennies, which is why the pure vinegar and cola will have cleaned their coins, while the water is ineffective.
Experiments also exist to turn pennies green, which is a process known as verdigris. Have students place two identical glass beakers next to one another and half fill one with tap water and half fill the other with pure vinegar with 2 tsps. of salt dissolved in it. Students should add a couple of pennies to each beaker and leave them for five minutes before straining the contents away and placing the pennies from each beaker on a separate paper towel without drying them. Instruct your sixth-grade students to leave the pennies for at least one week. observing them once each day to see the changes in each condition as all of the pennies start to turn a blue/green color. Where pennies were exposed to vinegar and water, the green pigment on the coin is called copper chloride, while the verdigris on the acetic acid pennies is called copper carbonate.
Use pennies to test the strength of a paper towel. This experiment features both scientific and consumer interest. Students should set up four standing clamps in a square to hold a paper towel by the four corners and hold it under tension. Provide your students with four different brands of paper towel, including economy and higher-quality brands, so they can test strength between the different paper towel brands. Students should damp the towel with a medicine dropper full of water before placing a penny in the center of the towel. Have students keep adding pennies one-by-one until the paper towel tears. Compare the performance for different towels and think about the cost of the towel related to its strength.
Students can investigate the basic properties of surface tension using a three drinking glasses: one each filled with water, milk and vegetable oil. To observe surface tension, fill the glasses right to the brim, before observing the brim of the glass through a magnifying glass. Get students to note the way the water bulges upward before adding one penny at a time while watching through a magnifying glass to observe the changes. Students should keep adding pennies until the liquid they are investigating spills over the edge. Challenge students to compare the surface tension of different liquids using the penny test.