1. Lemon juice is a juice made from fresh lemon juice, with a strong sour taste and a touch of bitterness and fragrance. Lemon juice contains sugar, vitamin C, vitamin B 1, B2, nicotinic acid, calcium, phosphorus, iron and other nutrients.
2. Give examples to illustrate the specific original text as follows:
Pour half a glass of water into the dish, then drop 10 drop of iodine and mix with water evenly. Then cut a lemon and squeeze the lemon juice into another clean cup. Find a piece of white paper and cut it into a size that can be put on a plate. Dip a small brush in lemon juice, and then write or draw on the paper. Dry the paper with words (or pictures) written on it. Finally, put the written and dried paper into a plate with iodine solution. As a result, the parts written in lemon on the paper are colorless, and the basic parts are blue and purple. It's like a painting and calligraphy in white.
3. Principle: The starch contained in the paper will react with iodine to form iodine starch molecules, which are dark blue and purple; Lemon juice is rich in vitamin C, which will be colorless when it reacts with iodine. So the part where you write or draw with lemon juice will not change color.