Experiment: How to make invisible inks from a lemon, milk and baking soda
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Observe fire safety rules when working with an iron and other heating devices.
Do you dream of being a top secret agent? Then you should certainly know how to read and write encrypted messages. In our experiment, we’ll show how cunning chemists can make invisible ink at home!
Reagents and equipment:
* baking soda;
* 3 beakers;
* 3 brushes;
For the experiment, we’ll need 3 small beakers. Pour a little milk into the first, lemon juice into the second, and the baking soda solution into the third. Then start to write secret messages on paper. Dip the brush into the first beaker and write with the liquid, and then with the liquids in the second and third beakers, leaving an invisible message on the paper. Several minutes later the letters dry out and the writing on the paper becomes completely invisible. To reveal the message, we just have to heat up the sheet of paper. We pass a heated iron over the sheet of paper, and after a while the writing appears in a bright brown color.
When the sheet of paper with invisible ink is heated, the breakdown of citric acid, milk and kitchen soda takes place. As a result of these chemical reactions, the products of their breakdown are released, which color the paper brown, making the secret message visible. This effect can also be observed when sugar is heated; it melts and turns dark, turning into caramel.