Demo: Gold Penny

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This is not so much a lesson but rather a demo. This is kind of a “Wow!” demo. The chemical composition of the penny has varied greatly through the years. From 1793 to 1837 it was actually pure carbon. It went through many changes since then. From 1864 to 1962 it was bronze (95 percent copper, 5 percent zinc and tin). In 1962 the penny’s tin content was removed, which made it 95 percent copper and 5 percent zinc. In 1982, the composition changed to 97.5 zinc and 2.5 percent copper (copper plated zinc). In this demo you need pre 1982 pennies (The US Mint has a good slideshow on how coins are made). The purpose of this demo is to give the penny a zinc plating, then heat it up to form a brass alloy so that it will look like gold. You can discuss in this demo the various properties of metals. Also you can discuss the technique of wet chemical plating, a technique first discovered by alchemist centuries ago, to try to fool people into believing they had the ability to change common metals into precious metals. This demo was taken from the Chemistry Demo a Day book.

Procedure:
1. Get the materials as shown in slide 1.
2. Mix about 24 g of sodium hydroxide into 200 ml of water. Use a 400 ml beaker. Heat the mixture on a medium low setting. Do not boil.
3. Mix in 5 g of granular zinc. (slide 2)
4. Place penny into beaker and stir for about 4 minutes (slide 3).
5. Use tongs to take out penny and place in water (slide 4). This stops the process. Rub penny with cloth to create a sheen. The penny is now zinc plated. It kind of looks like a silver penny (slide 6)
6. Use tongs to slowly heat penny over a Bunsen burner flame. Slowly move the penny back and forth across the flame. The heat makes the zinc atoms mix with the copper atoms to form a brass alloy. It looks kind of like gold (slide 6).
Tips: Have a student assistant help you with the procedure. They will have fun. Have pennies that have already been done, to pass out to students during the demo so they can have an up close look.

Tips: Have a student assistant help you with the procedure. They will have fun. Have pennies that have already been done, to pass out to students during the demo so they can have an up close look.

Safety: Make sure you and the student wear goggles, and know how to properly use a Bunsen burner safely. Make sure room is well ventilated.

Solar System Scale Model Tour

When students learn about the Solar System they have a difficult time visualizing or comprehending what the distances are like between the planets and the sizes of the planets and the Sun. Most textbooks show pictures of the planet on one scale and the distances between the planets on another scale. They never have them to the same scale. The reason why is that the Solar System is huge! There are a ton of Solar System scale model lessons on the web. One of the best is the half mile long model. In this model the following represent the planets (see slide show): Mercury, Mars, and Pluto = head of pin, Earth and Mars = peppercorn, Jupiter = rubber ball, Saturn = hazelnut, Uranus and Neptune = peanut, Sun = volleyball. I glued these items (except the volleyball) to paper plates. I then made a flag for each planet out of wooden dowels and construction paper. I then inserted the flags through the middle of the paper plates and set the combination into a PE cone (see slide show). The distance between the planets are on the teacher handout (students have a separate handout). I have my students record into a lab composition book a journal of their tour. They answer questions before, during and after the tour. They are pretty amazed by the size of the model (see slide show). You need to have a pretty straight stretch of street (see slide show) to use, that isn’t too busy. I give my principal notice ahead of time and I also bring a first aid kit.

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Pseudo Lava Lamps

This is from a terrific site, Steve Spangler Science. I do many density demos and lessons and I am going to try this one this year.

“ProjectsFizz, Bubble, Erupt! Learn how to make an inexpensive science toy that will be a guaranteed hit with the kids! Ok, so everyone knows that oil and water don’t mix. Try adding a few drops of food coloring and a little Alka-Seltzer fizz to the solution and the bubbling concoction is guaranteed to provoke a few ooohs & ahhhs!”

Steve Spangler Science Experiment Fizz, Bubble, Erupt!

Video Demo: Burning Iron

Many of the demos that I use in teaching chemical reaction are taken from a terrific book called A Demo A Day–Chemical Demonstration Book. The book contains a year’s worth of chemistry demonstrations that are easy to follow and to use. This demonstration shows that when iron has a large surface area it can react with oxygen and burn easily. I first use the 9 volt battery and touch the ends to various steel surfaces. The students see that nothing happens. I then touch the battery to the steel wool (held by the clamp on the ring stand) and the battery provides enough energy to make the iron burn. The steel wool has a larger surface area than pieces of steel like the ring stand. The steel wool is exposed to more oxygen molecules. You can also use this as a conservation of mass demo. Simply place the steel wool in a plastic bag and measure the mass. After burning the wool (of course it shouldn’t be in the bag at this point) return the leftover material back in the bag and mass it again. The mass should be the same (although it might be greater afterwards, since oxygen has now bonded with the iron.).

Preparations: You may have to soak the steel wool in acetone for 15-20 minutes to remove the outer coating, so that the steel is exposed. Take the wool out of the acetone and left it air dry.

Video Demo: Disappearing Cup

Many of the demos that I use in teaching chemical reaction are taken from a terrific book called A Demo A Day–Chemical Demonstration Book. The book contains a year’s worth of chemistry demonstrations that are easy to follow and to use. This demonstration shows the concepts of polymers. Styrofoam is an example of a polymer. A polymer is made up of monomers. You can think of a monomer as a Lego piece. When you connect the Lego pieces together you have a polymer. You can take a Styrofoam cup and place it in a petri dish of acetone. Push down on the cup and the cup seems to disappear! The acetone is breaking the bonds between the monomers.

Precautions: Acetone is flammable and needs to be used in a well ventilated area. Wear goggles.

Watch the Google video.