Students were given
blank papers each and were asked to write on it with lemon juice using cotton
and let it dry. Nothing was visible once it dried. Then when hot
air was blown on the write up, it turned to a slight brown colour and
could be read.
When they wrote the
message using the lemon juice, carbon-based compounds in the juice were
absorbed into the papers fibers. The added heat caused some of the chemical
bonds to break down in the dried juice and some carbon was cut loose. When the
carbon came into contact with air, it burned or oxidised and the substance
turns light or dark brown.
Children understood
the process of oxidation.
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