What is the name of a paper that changes color when exposed to sunlight?

No, it should be a high school chemistry test that starch will turn blue when exposed to iodine, and iodine is easy to sublimate;

So that paper should be starch and iodine (green?). Theoretically, it should be blue), when iodine is gradually sublimated by the increase in light and temperature, the paper loses its color, and the starch has no color, so it becomes the natural color of the paper - white.

There is a lot of starch in potatoes, and you can do this at home.

It was this phenomenon that led to the discovery of photosynthesis.

The discovery of photosynthesis until the mid-18th century, when people thought that all the nutrients in plants were obtained from the soil, and it was not thought that plants could get anything from the air. In 1771, the British scientist Priestley discovered that the candle was not easily extinguished by placing the lit candle in a closed glass cover with the greenery; Place the mouse inside a glass cover with greenery, and the mouse is also not easily suffocated. Thus, he points out that plants can renew the air.

However, he did not know what composition of the air was renewed by the plants, nor did he discover the key role that light played in this process. Later, after many scientists' experiments, the places, conditions, raw materials and products of photosynthesis were gradually discovered. In 1864, the German scientist Sachs did such an experiment:

Keep the green leaves in the dark for a few hours to allow the nutrients in the leaves to be depleted. Then put half of this blade** and the other half shaded. After a period of time, the leaves were treated with iodine vapor, and it was found that the shading half of the leaves did not change color, and the ** half of the leaves was dark blue.

This experiment successfully demonstrated that green leaves produce starch during photosynthesis.

Changes in color, depth, or brightness due to sunlight exposure or gas fumigation in the air. After aging in the atmosphere, the general color gradually becomes lighter, mainly affected by ultraviolet light. The influence of atmospheric temperature, humidity, impurities (acidic, alkaline), and changes in the properties of organic substances such as pigments.

The key to preventing fading is to choose pigments that are stable and do not fade easily.

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Problem description: Please explain to me in detail if the change is a chemical change, please tell me the chemical reaction equation. Thank you.

Analysis: The bleaching of the pulp is Jingzheng Li using sodium metabisulfite as a bleaching agent, and the pulp is dried to form paper The paper contains a small amount of residual sulfur dioxide, and the amount of brightness is very small It plays a role in reducing other pigments and keeping the paper white Needless to say, it is dried in the sun, even if it is left for a long time, it will also turn yellow It is sulfur dioxide that is free to go out

At present, research has found that very white paper will cause damage to people's eyesight, and the use of yellowed paper to print, this is not a technical failure, but caused by the innovation of paper technology Generally, genuine textbooks are made of yellowed paper, and watermarks are used on the second cover to prevent counterfeiting, such as self-examination textbooks Clear.

The bleaching of pulp is made with sodium metabisulfite as a bleaching agent.

After the pulp is dried, the paper contains a small amount of residual sulfur dioxide.

The amount is very small It plays a role in restoring other pigments and keeping the paper white and clean Needless to say, if it is dried in the sun, even if it is left for a long time, it will also change Zheng Huang is sulfur dioxide free out

At present, research has found that very white paper will cause damage to people's eyesight, and the use of yellowed paper to print, which is not a technical failure, but caused by the innovation of paper technology Generally, Soyousong genuine textbooks are made of yellowed paper, and watermarks are used on the second cover to prevent counterfeiting, such as self-examination textbooks

Phenomenon: When a wet blue test strip is baked with a match, the test strip turns light red.

Method: Before the performance, the performer takes a blue litmus test paper, soaks it in water, and sets aside. Take another box of matches for later use.

During the performance, the performer first shows the test strip and match to the audience, then lights a fire and places the wet blue litmus test paper above the match flame. After a while, the audience noticed that the blue test strip had turned light red.

Principle: When a match is burned in the air, carbon dioxide is generated, and carbon dioxide reacts with the water on the test strip to form carbonic acid. Carbonic acid is a weak acid that can make blue litmus paper red.