To conduct this experiment, follow these steps:

1. Spread a moist paste of potassium iodide and starch on a conducting metal plate.


2. Connect the plate to a battery as shown in the diagram.


3. Using a free wire, write a few letters on the paste.


4. Observe the changes in the paste.

When the conducting metal plate is connected to the battery, it creates an electric field. The moist paste of potassium iodide and starch on the plate is a conductor, and it reacts to the electric field by producing a chemical reaction. The iodine ions move towards the positive electrode, and the starch molecules form a complex with the iodine ions, causing a change in color.

As we write letters on the paste using a free wire, the electric field creates a pattern of iodine ions and starch molecules, resulting in a visible change in color. The areas where the free wire touches the paste turn dark blue, while the areas where the wire does not touch the paste remain unchanged.


The experiment demonstrates the principles of electrochemistry. When the conducting metal plate is connected to the battery, it creates a voltage difference between the positive and negative electrodes. This voltage difference creates an electric field that causes the movement of ions and electrons in the conducting paste.

The potassium iodide and starch paste is a conductor, meaning it can carry an electric current. When the electric field is applied, the iodine ions in the paste move towards the positive electrode, creating a visible change in color. The starch molecules in the paste form a complex with the iodine ions, causing the blue color.

When we write letters on the paste using a free wire, we create a pattern of electric field that causes the movement of ions and electrons in the paste. The areas where the wire touches the paste have a higher concentration of iodine ions, resulting in a darker blue color. The areas where the wire does not touch the paste have a lower concentration of iodine ions and remain unchanged.

In conclusion, the experiment demonstrates the principles of electrochemistry and how electric fields can cause chemical reactions in conductive materials. The observation of the change in color in the paste helps us understand the movement of ions and electrons in the material.

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