Little chemical facts in daily life

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Little chemical facts in everyday life: People need materials for their clothing, food, shelter, and transportation; a rich material world enables us to lead a colorful life. By studying chemistry, you’ll realize that it’s actually all around us. Chemical substances are widely related to various aspects such as production and daily life, as well as environmental protection, the utilization of energy and resources, and medicine, health, and human well-being. There are many basic chemical facts in life that we need to understand. 1. Use of iodized salt. Iodine is an essential nutrient for the human body; a long-term deficiency in iodine can lead to iodine deficiency disorders. Consuming iodized salt is the simplest, most economical, and effective way to eliminate iodine deficiency disorders. Iodized salt contains sodium chloride and potassium iodate; the iodine needed by the human body is provided by potassium iodate. However, potassium iodate is unstable and prone to decomposition when exposed to heat or light, which can affect the body’s intake of iodine. Therefore, when cooking, it is important to add salt near the end of cooking time, and to avoid prolonged cooking. 2. Tofu should not be cooked with spinach. Calcium oxalate is a precipitate that cannot be absorbed in the human body. Spinach, onions, and bamboo shoots are rich in oxalic acid and sodium oxalate, while tofu contains a high amount of calcium salts, such as calcium sulfate. The aforementioned substances can undergo double-displacement reactions to produce substances such as calcium oxalate precipitate. From a medical perspective: Spinach, onions, bamboo shoots, and similar foods should not be consumed together with tofu, as this can lead to the formation of calcium oxalate deposits, which are a cause of kidney stones ； From a nutritional perspective, mixing them together will destroy their nutritional components. 3. The harms of aluminum to human health. Aluminum has long been considered a non-toxic element, which is why aluminum kitchenware, aluminum-based leavening agents, water purifiers, and similar products are widely used. However, studies in recent years have shown that aluminum can disrupt the body’s metabolic processes, causing gradual harm to health over time. The toxicity it induces is slow and hard to detect; yet once toxic metabolic disorders occur, the consequences can be severe. To prevent aluminum poisoning, the following precautions should be taken in daily life: (1) Reduce the sources of aluminum intake, such as eating fewer fried dough sticks, and avoid medications for treating stomach problems that contain aluminum hydroxide. (2) Consume fewer foods packaged in aluminum. (3) Use aluminum products in moderation, and avoid prolonged contact between food or drinking water and aluminum products. 4. Fruits can help alleviate the effects of alcohol because they contain organic acids. For example, apples contain malic acid, citrus fruits contain citric acid, and grapes contain tartaric acid. The main component of alcohol is ethanol, and organic acids can interact with ethanol to form esters, thereby helping to reduce the effects of alcohol. By the same principle, vinegar can also help relieve the effects of alcohol, as it contains 3–5% acetic acid, which can undergo an esterification reaction with ethanol to produce ethyl acetate. 5. When cooking, the oil should not be heated to the point where it starts smoking; at high temperatures, oils tend to form polycyclic compounds. Vegetable oils, which contain a high amount of unsaturated fatty acids, are more prone to forming such compounds. Experiments have shown that polycyclic compounds can easily induce bladder cancer in animals. Generally, just bring the oil to a boil, and the impurities in the oil will be removed. 6. Why do “red tides” occur in seawater? In recent years, large-scale red tides have occurred in coastal waters such as the Bohai Bay in our country, a phenomenon known as \"red tide\". Red tide is not a tidal phenomenon, nor is it a current movement like the Kuroshio Current; rather, it is a biological phenomenon in which red plankton in the ocean reproduce excessively under certain conditions. Why can plankton reproduce in excess? It turns out that the large amounts of wastewater and waste materials that flow into the oceans, as well as the substances that reach the oceans through atmospheric exchange, contain elements such as nitrogen and phosphorus, which are essential nutrients for plant growth. As a result, the plankton multiply rapidly in large numbers, causing the sea to take on a \"red hue\". To prevent marine red tides, it is necessary to control the discharge into the ocean of wastes containing nitrogen, phosphorus, and other substances, such as wastewater from phosphorus-containing detergents, in order to maintain the ecological balance in the oceans. 7. The acidity or alkalinity of food. Research has shown that consuming more alkaline foods can help maintain a slightly alkaline pH in the blood, reducing the amount of acidic substances such as lactic acid and urea in it. This prevents these substances from accumulating on the walls of blood vessels, thereby helping to soften them. For this reason, some people refer to alkaline foods as \"cleaners for the blood and blood vessels.\" Generally speaking, foods such as rice, flour, meat, fish, and eggs are almost all acidic, while vegetables, fruits, milk, sweet potatoes, potatoes, soy products, and aquatic products are all alkaline. By paying attention to a scientific diet, improving the food structure, increasing physical exercise, and developing good living habits, the progression of arteriosclerosis can be delayed or even reversed. The pH level of human body fluids is closely related to IQ levels. Within the acceptable range of body fluid pH, those with a higher acidic level have lower IQ, while those with a higher alkaline level have higher IQ. Scientists tested dozens of boys aged 6 to 13, and the results showed that children whose cerebral cortex fluid had a pH level greater than 7.0 had an IQ that was more than twice as high as that of children whose pH level was below 7.0. Some children with poor academic performance and lower levels of intellectual development tend to have an acidic body constitution. 8. Sulfur dioxide in food. Sulfur dioxide is an important member among inorganic chemical preservatives. Sulfur dioxide has been used as a food additive for several centuries; the earliest records date back to the Roman era, where it was used to disinfect wine containers. Later, it was widely used in food, such as for sulfur fumigation during the production of dried fruits and preserved fruits ； It is made into a sulfur dioxide release agent for the fresh-keeping storage of fruits such as grapes. Sulfur dioxide can exhibit various technical effects in foods; it is generally referred to as a bleaching agent, as it can react with colored substances to bleach foods. On the other hand, sulfur dioxide has a reducing effect; it can inhibit the activity of oxidases, thereby preventing enzymatic browning. In short, since the use of sulfur dioxide enables dried fruits and preserved fruits to have an attractive appearance, it is sometimes referred to as a cosmetic additive. While exerting a \"preservative\" effect, sulfur dioxide also has many other functions beyond preservation, such as anti-oxidation, which are essential for maintaining the nutritional value and quality of food. For a long time, it was believed that sulfur dioxide was harmless to the human body, but after Baker and others discovered in 1981 that sulfites could trigger asthma attacks in some patients with asthma, the safety of sulfur dioxide was re-evaluated. Based on long-term toxicology studies, it is believed that sulfite preparations, at their current levels of use, pose no significant hazard to most people. Two more points should be noted: sulfites in food must reach a certain level before they can cause allergies. Even those who are highly sensitive to sulfites are not allergic to all foods treated with sulfites. From this perspective, sulfur dioxide is a relatively safe preservative. 9. Why does table salt deliquesce? How to prevent it from deliquescing? Magnesium chloride is often contained in table salt. Magnesium chloride deliquesces in air. To prevent table salt from deliquescing, it is generally advisable to dry-fry it in a pot. Due to the complete hydrolysis of magnesium chloride into magnesium oxide (MgO) at high temperatures, it loses its deliquescence. Or, table salt can be purified; pure sodium chloride does not exhibit deliquescence in air. 10. Formation of scale. Calcium bicarbonate is dissolved in the water, and it’s completely invisible. But when water containing calcium bicarbonate is heated in a pot, the calcium bicarbonate gradually decomposes upon heating, returning to its original components: carbon dioxide, water, and calcium carbonate. When this water containing calcium carbonate is placed in a teapot or thermos, the calcium carbonate gradually settles at the bottom of the container or adheres to its inner walls. Over time, this accumulation of calcium carbonate forms what is known as \"tea scale\". So, why can hydrochloric acid remove calcium carbonate? This is another chemical reaction that produces a new substance called calcium chloride. Calcium chloride can dissolve in water, so it disappears just by washing it with water. In this way, the \"tea scale\" is removed. Use hydrochloric acid to remove \"tea scale\". It should be noted that, first of all, do not use your hands to wipe directly; it is better to use a cloth wrapped around a copper wire for cleaning. Secondly, the hydrochloric acid should be made dilute – it cannot be too concentrated, nor should there be too much of it, as hydrochloric acid is corrosive. After removing the \"tea scale,\" it is necessary to rinse thoroughly several times with water in order to get rid of the hydrochloric acid ； Or fill a teapot with water and add a few iron nails; after a few days, the remaining hydrochloric acid will be gone.