Comet Demo

This is one of the few times that students have an opportunity to touch what an object in the Solar System is kind of like. This demo is very popular and can be found all over the Internet. The materials that are needed are shown in slide show (plus 2 large cups of water). Mix the water, sand, 1 tablespoon of corn syrup, and a dash of ammonia into the bowl (see slide show). These are the main ingredients of a comet. Of course the temperature needs to be decreased dramatically. Dry ice, frozen carbon dioxide, will do this and is also an ingredient. The dry ice needs to be placed into the double heavy duty trash bags (see slide show). Use the hammer to crush the dry ice into a powder (see slide show). Then carefully pour the dry ice into the plastic bowl (see slide show). Using the gloves shape the mixture into a ball (see slide show). Carefully remove the comet and let students touch it. The comet really is the nucleus of the comet–the solid part. Explain to the students that the Sun’s energy heats up the ice to form the gaseous coma, which can be seen in this demo.

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Video Demo: Glowing Penny

Another great demo from the Demo a Day: Chemistry Demonstration Book. To get chemical reactions started activation energy is needed. During a chemical reaction, heat energy is often released (exothermic) or absorbed (endothermic). To get this reaction started, a pre 1982 penny is heated over a Bunsen burner. The penny is wrapped in copper wire and held over the flame with tongs. Once the penny is heated, it is then placed into the 125 ml flask that contains a small amount of acetone liquid at the bottom. The penny does not touch the acetone, but is just above the surface. The copper in the penny reacts with the acetone fumes to produce a very exothermic reaction where the penny glows. The penny will continue to do this for several minutes.

Preparations: Make sure you adjust the penny and the copper wire so the penny just sits above the acetone. Do this before you heat the penny.

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Video Demo: Diffusion

See 2 video demonstrations of diffusion in action. The first video shows a drop of food coloring diffusing through water. It is a video that is time lapsed at 1 frame/15 seconds. The second video shows a Ziploc bag of iodine placed into a beaker of starch water. It is a video that is time lapsed at 1 frame/30 seconds. The iodine diffuses out of the bag and into the starch water. Where the iodine is diffusing the starch water turns a dark blue.

Video Demo: 7 Inertia Demos

This video clip shows 7 demonstrations of Newton’s first law of motion–the law of inertia. Newton’s law of inertia states that objects moving at constant velocity will continue moving at constant velocity, unless acted upon by an outside unbalanced force. Six of these demonstrations (excluding demo 6) are from Tik Liem’s book Invitations to Science Inquiry. I have students volunteer to do all demos, except demo 5. All of the students in class receive a handout that they must fill in so that they understand how inertia is demonstrated and all the forces that are involved.

Video Demo: Cola Volcano

Signs of a chemical reaction include color change, gas production, temperature change, precipitation, and other changes in properties …including density, taste, texture, smell, melting point, boiling point, etc. This demonstration will really make them think about it. Place a large plastic container on the counter. Invert a large jar or beaker into the container. Set a 3/4 full liter of fresh cola on top. Carefully but quickly pour a cupful of sugar into the soda and stand back. The cola will burst out of the bottle. Most students will assume it is a gas production sense they can see all of the foam. Have the students taste the left over soda. It is very sweet and very flat, indicating the soda is still there and the carbon dioxide left. It is a physical change and not a chemical change. The sugar pushes out all of the carbon dioxide gas.