Convection box

Relevant Resource questions :

Concepts demonstrated :

• change of state
• Latent heat
• convection

• test tube
• test tube holder
• wire gauze or helical coil to hold ice at the bottom of the test tube
• bunsen burner and matches
• CCD camera

• Place the ice at the bottom of the test tube and fix it there using the wire gauze or coil.
• Fill the test tube with water.
• Position the bunsen burner so that only the top half is heated.

None.

Physics involved :

The ice at the bottom of the beaker will not melt because convection will not occur. This is even true if the water at the top is boiling. The test tube will be hotter at the top and therefore there is no need for convection to occur.

How to use the Demonstration :

• POE - ask the students what they think will happen when the test tube is heated.
• Perform the experiment showing that the ice does not melt.
• Ask them to explain why the ice does not melt.

Things to do or add :

• Replace the test tube with a beaker, and use a thermocouple linked to a computer to display temperature (T) versus time (t).
• Plot a temperature versus time graph showing that temperature only rises when the change of state occurs.