This experiment will allow students to draw a picture or write a message that will be invisible until a source of heat is applied to the paper. Most invisible ink messages can be revealed by heating either side of the paper on which they’re written. The message discolors before the rest of the paper gets hot enough to do so. In this experiment, we are using the naturally acid nature of lemon juice to act as our ink. When placed on the paper, the water from the lemon juice evaporates to leave behind the citric acid present in the juice. These carbon-based compounds in the juice were absorbed into the paper’s fibers.. Citric acid compounds are pretty much colorless at room temperature. The acid reacts with the fibres of the paper, weakening and damaging them. some of the chemical bonds start to break down in the dried juice and some carbon was cut loose. When the carbon came into contact with air, it oxidized. One effect of oxidation is things turn a darker color. (Some oxidation doesn’t need heat to occur; it just needs a little air. Think of a piece of apple, banana, or pear left out on a plate for a while.) As a result of this oxidation, when an external heat source is applied, the "juiced" areas of the paper burn much more rapidly than the untreated paper, revealing the initial message as brown areas on the paper.
- Acids – this experiment relies on the acidic nature of lemon juice
- Chemical reactions are temperature dependent – this reaction highlights the dependency of the rate of a chemical reaction on temperature
From Secret Message with Lemon Juice – SICK Science
From Common Sense Media
Ben Gates (Nicholas Cage) comes from a long line of treasure hunters who have been been chasing a legendary treasure for generations. Ben is determined to solve the mystery with the help of his sidekick Riley (Justin Batha) and an unlikely ally played by Diane Kruger, who is the guardian of the Declaration of Independence. Meanwhile Ben's former colleague and financial backer, Ian (Sean Bean), has betrayed Ben and is trying to find the treasure for himself. With ingenuity, some help from family and friends, and a lot of luck, Ben and his crew might just solve the legend and find the treasure before his enemies do. Along the way, the treasure hunt will take them to historic sites in Washington, Philadelphia, Boston, and New York, from the highest of high-tech security to the ricketiest of ancient catacombs.
"Oxygen-rich environments accelerate degradation, so preservation experts sometimes store artifacts in encasements where the oxygen has been removed. Controlling moisture is also critical."
Documents such as the Declaration of Independence are in an "enclosure [that] is hermetically sealed and filled with the inert gas argon instead of oxygen, because oxygen reacts with the materials in paper and ink to degrade them. The argon maintains the atmospheric pressure that the air would normally exert on the map."
"Sensors monitor the environment inside the encasement, alerting staff if conditions veer into dangerous degradation territory"