Thermal Conductivity Demonstrations
This material was originally created for
Starting Point:Introductory Geology and is replicated here as part of the SERC Pedagogic Service.
This Starting Point page was organized by R.M. MacKay. Clark College, Physics and Meteorology.
II. This is a fun demonstration of thermal conductivity. Attach a copper (or aluminum) rod end-to-end to a wooden dowel of the same diameter by wrapping a piece of paper around each. Use a Bunsen burner or hand-held butane torch for the flame. III. This JAVA simulation of 2-D heat transfer can be used as a follow-up to either demonstration above.
IV.Boiling water in a paper cup. Fill a paper cup about half to two-thirds full of water. When set over a flame the water boils but the paper in contact with the water does not catch fire. Use a Bunsen burner or hand-held butane torch for the flame. Heating from the side works well also when you use a full cup to keep the top from burning.
II. A rod made of half copper and half wood is wrapped in paper. Expose the composite bar to flame near the junction until it is clear that the wood side burns and the copper side does not. Make sure that the paper wraps around the bar's circumference just one time or a little less. Overlapping paper will likely ignite regardless of whether the bar underneath is wood or copper. You can also wrap the paper around the wood and cooper bars separately and show that the paper burns when wrapped around wood but does not when wrapped around copper. This makes it easy if you don't have wood and copper bars of the same diameter. III. This JAVA simulation of 2-D heat transfer Instructions are provided for users to create their own simulation but it is also set up with a ready to go simulation. IV. Boiling water in a paper cup. If the cup is too thick it will be scorched on the outside. Do not use a waxed paper cup. Also, paper cups with a smooth bottom (without the bottom indentation) work best since any paper not in direct contact with water will likely burn when set in a flame.
Conductivity Bars from Boreal Laboratories are a fairly low cost ready made setup for the semiquantitative measure of heat fow down bars made of different materials.
This link from NASA shows a variation of heat conduction down a rod. Screws that have been hot glued fall off a rod after one end is inserted into a flame.
II. Here's a video (AVI 4.2 Megs) showing water boiling in a paper cup that is heated from the side.
Summary
Here are three ideas for demonstrating thermal conductivity to your students.
I. Heat flow down a metal rod (or rods) is timed by seeing wax melt at different locations along the rod. II. A rod made of half copper and half wood is wrapped in paper. When exposed to flame the wood side burns and the copper side does not. III. A JAVA simulation of 2-D heat transfer can be used as a follow-up to either demonstration above. IV. Boiling water in a paper cup.How to set up the demonstration
I. In the first demonstration, heat flow down a metal rod (or rods) is timed by seeing wax melt at different locations along the rod. This link from the university consortium for atmospheric research (UCAR) shows how to set up this demonstration. (more info) .II. This is a fun demonstration of thermal conductivity. Attach a copper (or aluminum) rod end-to-end to a wooden dowel of the same diameter by wrapping a piece of paper around each. Use a Bunsen burner or hand-held butane torch for the flame. III. This JAVA simulation of 2-D heat transfer can be used as a follow-up to either demonstration above.
IV.Boiling water in a paper cup. Fill a paper cup about half to two-thirds full of water. When set over a flame the water boils but the paper in contact with the water does not catch fire. Use a Bunsen burner or hand-held butane torch for the flame. Heating from the side works well also when you use a full cup to keep the top from burning. How to do the demonstration
I. This link from the university consortium for atmospheric research (UCAR) discusses how to do this demonstration. (more info)II. A rod made of half copper and half wood is wrapped in paper. Expose the composite bar to flame near the junction until it is clear that the wood side burns and the copper side does not. Make sure that the paper wraps around the bar's circumference just one time or a little less. Overlapping paper will likely ignite regardless of whether the bar underneath is wood or copper. You can also wrap the paper around the wood and cooper bars separately and show that the paper burns when wrapped around wood but does not when wrapped around copper. This makes it easy if you don't have wood and copper bars of the same diameter. III. This JAVA simulation of 2-D heat transfer Instructions are provided for users to create their own simulation but it is also set up with a ready to go simulation. IV. Boiling water in a paper cup. If the cup is too thick it will be scorched on the outside. Do not use a waxed paper cup. Also, paper cups with a smooth bottom (without the bottom indentation) work best since any paper not in direct contact with water will likely burn when set in a flame.