Common sense of chemistry in life

Why is the old sweet potato sweeter than the newly dug sweet potato? Everyone has this experience. A long-standing sweet potato is always sweeter than a newly dug sweet potato. What is the reason? We can intuitively see that sweet potatoes have been stored for a long time, the water content has decreased a lot, and wrinkles have appeared on the skin.

The decrease of water has a great influence on the improvement of sweetness for two reasons: First, the decrease of water evaporation increases the sugar concentration in sweet potato. Second, in the process of placing, water participated in the hydrolysis reaction of starch in sweet potato, and the starch was hydrolyzed into sugar, which increased the sugar in sweet potato.

So we think the sweet potato with a long history is sweeter than the newly excavated sweet potato. When cooking, it is not advisable to burn oil and smoke. When cooking, some people like to burn the oil to smoke or even burn it quickly before putting the vegetables, especially when using vegetable oil, because they think that if they don't burn the "dead" vegetables, there will be oil and gas.

It should be pointed out that this is a bad practice. Oil is easy to form polycyclic compounds at high temperature. Generally, vegetable oil contains more unsaturated fatty acids, which makes it easier to form polycyclic compounds. Experiments show that polycyclic compounds are easy to induce animal bladder cancer. Generally, as long as the oil is boiled, the "internal heat" of the oil can be removed.

The practical value of salt is not only an important chemical raw material, but also an important condiment in human life. In addition, salt has many uses.

(1) Drinking a cup of salty boiled water in the morning can cure constipation. Drinking salty boiled water can cure sore throat and toothache.

(2) Eating by mistake is toxic, and drinking salty boiled water has detoxification effect. (3) gargling with light salt boiled water every day can prevent various oral diseases.

(4) When taking a bath, adding a small amount of salt to the water can make the skin firm. (5) Tofu goes bad easily. For example, if salt is dissolved in boiling water, tofu can be preserved for several months even in summer.

(6) Peanut oil contains water, which will stink if it is left for a long time. You can fry the salt, let it cool, and add salt according to the ratio of 40 kg oil 1 kg salt, which can keep peanut oil smooth and delicious for 2-3 years.

(7) Flowers can be inserted in light salt water for several days. (8) Newly bought glassware, boiled with salt, is not fragile.

(9) When washing colored clothes, soak them in 5% salt water for 10 minute, and then wash them, so that the color will not fade easily. (10) When washing white clothes with sweat stains, rub them with 5% salt water first, and then wash them with soap, so that yellow sweat stains will not appear.

(1 1) Mash carrots, mix them with salt, and wipe the blood on clothes. (12) Bronze is rusty or has black spots, which can be wiped off with salt.

Why do mung beans turn black after being cooked in an iron pot? After apples and pears are cut with iron knives, their surfaces will also turn black. This is because the cells of mung beans, apples, pears and various fruits all contain tannic acid, which can react with iron to produce black iron tannic acid.

When mung beans are cooked in an iron pot, they will produce some black iron tannins, so they will turn black. Sometimes, pears and persimmons will have some black spots on their skins even if they are not cut with an iron knife. This is because tannic acid molecules contain many phenolic hydrocarbon groups, which are very sensitive to light and are easily oxidized by oxygen in the air and become black oxides.

Milk should not be cooked at high temperature for too long. Milk is rich in protein. When heated, colloidal protein particles will change greatly.

When the temperature of milk reached 60-62 degrees, slight dehydration began, and protein particles changed from sol state to gel state, resulting in precipitation. Milk also contains unstable phosphate.

When heated, acidic calcium phosphate becomes neutral calcium phosphate, which will also be precipitated in the form of insoluble precipitate. In addition, when the milk is heated to about 100℃, the lactose in the milk begins to coke, which makes the milk have leg color and gradually decomposes into lactic acid, and at the same time produces a small amount of formic acid, which makes the milk sour.

So don't boil the milk for too long. Sterilization of Garlic Garlic is rich in protein, fat, sugar and vitamins A, B and C, etc. Garlic seedlings also contain calcium, phosphorus, iron and other ingredients.

Garlic has strong bactericidal power, because garlic contains garlic oil, which is mainly composed of propylene sulfide, and also contains a small amount of propylene disulfide and propylene disulfide. Allicin will decompose when it is heated by alkali, so raw garlic should be used for anti-inflammatory and sterilization, and it can't be used with alkaline substances.

Garlic tastes in your mouth after eating it. You can put a little tea in your mouth and chew it carefully, or you can put a piece of sugar in your mouth to reduce the garlic flavor. You can't drink boiled water. The water for steaming steamed bread or side dishes at home is called boiled water.

This kind of boiler water can't be drunk, nor can it be used for cooking rice or porridge. What is the reason? As we all know, water contains trace amounts of nitrate. When water is heated for a long time, the concentration of nitrate increases relatively due to the continuous evaporation of water, and it is decomposed into nitrite by heating. Nitrite does great harm to human health.

It can denature hemoglobin in human blood and can no longer combine with oxygen, leading to early hypoxia. Nitrite can also reduce human blood pressure, which can lead to collapse in severe cases.

Modern medicine has proved that nitrite is also a strong carcinogen. Therefore, boiler water cannot be drunk.

How to remove the bitterness of fish gall People like to eat fish because it tastes delicious. However, if you accidentally break the gallbladder when cutting fish and bile sticks to the fish, it will make the fish bitter and affect people's appetite.

Bile acid is the main component of bitterness in bile, because it is insoluble in water, so it is difficult to wash away bile that has penetrated into fish with water. Sodium carbonate can react with bile acid, and the product is sodium cholate, which is easily soluble in water.

Therefore, if the fish bile is broken, just put some baking soda powder on the fish with bile and rinse it with water later, and the bitterness can be eliminated. If the bile pollution area is large, fish can be soaked in dilute alkali solution for a while, and then washed, and the bitterness can be completely eliminated.

Four taboos for drinking soybean milk 1. Avoid washing eggs: Mucinous protein in eggs easily combines with trypsin in soybean milk to produce a substance that is not absorbed by the human body, thus losing its nutritional value. 2, avoid cooking: soybean milk contains trypsin inhibitor, if not cooked thoroughly, people will have symptoms such as nausea, vomiting, diarrhea.

3. Avoid brewing brown sugar. Because the organic acid in brown sugar can combine with protein in soybean milk to produce "denatured precipitation powder", brown sugar is forbidden to brew, while white sugar has no such phenomenon. 4. Avoid excessive drinking: If you drink too much soybean milk at one time, it will easily lead to "protein's indigestion due to overeating", diarrhea and abdominal distension.

2. Ask for tips on chemistry 100 tips on chemistry.

First, the chemical maximum is 1. The most abundant metal element in the earth's crust is aluminum. 2. The most abundant nonmetallic element in the earth's crust is oxygen. The most abundant substance in the air is nitrogen. The hardest substance in nature is diamond. 5. The simplest organic matter is methane. 6. The most active metal in the metal activity sequence table is potassium. 7. The oxide with the lowest relative molecular weight is water. 8. Under the same conditions. The most conductive metal is silver. 10. The atom with the smallest relative atomic mass is hydrogen. 1 1. The metal with the lowest melting point is mercury. 12. The most abundant element in human body is oxygen. 13. The element with the most kinds of compounds is carbon. 14. The three kinds of particles that make up matter are molecules, atoms and ions. 2. Hydrogen, carbon monoxide and carbon. 3 and hydrogen, which are often used to reduce copper oxide, have three advantages as fuel: rich resources, high calorific value, and the product after combustion is water, which does not pollute the environment. There are generally three kinds of particles that make up atoms: protons, neutrons and electrons. There are only three kinds of ferrous metals: iron, manganese and chromium. Elements that make up a substance can be divided into three categories, namely (1) metallic elements, (2) nonmetallic elements and (3) rare gas elements. 7. There are three kinds of iron oxides, the chemical formula is (1)FeO, (2)Fe2O3, (3) Fe3O4.8, and the characteristic of the solution is three (65434). (2) stability; (3) mixture. 9. The chemical equation has three meanings: (1) indicates what substances participate in the reaction and what substances are generated as a result; (2) The particle number ratio of molecules or atoms between reactants and products; (3) Represents the mass ratio of reactants to products. Chemical equations have two principles: based on objective facts; According to the law of conservation of mass, pig iron can be generally divided into three types: white iron, gray iron, ductile iron, carbon steel, high carbon steel, medium carbon steel, low carbon steel, and iron ore commonly used in ironmaking. (2) Magnetite (Fe3O4); (3) siderite (FeCO3). 13. There are mainly three kinds of steelmaking equipment: converter, electric furnace and open hearth furnace. 14. The three reaction conditions that are often related to temperature are ignition, heating and high temperature. 15. There are two ways to change saturated solution into unsaturated solution: (65438+. There are three ways to change unsaturated solution into saturated solution: cooling, adding solute and evaporating solvent at constant temperature. (Note: For substances whose solubility decreases with temperature, such as calcium hydroxide solution changing from saturated solution to unsaturated solution: cool and add solvent; There are three ways to change unsaturated solution into saturated solution: raising temperature, adding solute and evaporating solvent at constant temperature) 16. There are generally three ways to collect gas: drainage, upward evacuation and downward evacuation. 17. There are three main reasons for water pollution: (1) waste residue, waste gas and waste water in industrial production; (2) Discharging domestic sewage at will; (3) Pesticides and fertilizers used in agricultural production flow into rivers with rainwater 18 There are three kinds of fire extinguishers commonly used: foam extinguisher; Dry powder fire extinguisher; Liquid carbon dioxide fire extinguisher. 19. The solubility of solid substances can be divided into three categories with the change of temperature: (1) The solubility of most solid substances increases with the increase of temperature; (2) The solubility of a few substances is little affected by temperature; (3) The solubility of a few substances decreases with the increase of temperature. 20. There are three reasons why CO2 can put out a fire: it can't burn, it can't help combustion, and its density is higher than that of air. 2 1. Simple substances can be divided into three categories: metallic simple substances; Non-metallic simple substance; Rare gas elements. 22. The three most important fossil fuels in the world today are coal, oil and natural gas. 23. The three black oxides that should be remembered are copper oxide, manganese dioxide and ferroferric oxide. 24. Hydrogen and carbon have three similar chemical properties: stability at room temperature, flammability and reducibility. 25. There are three kinds of light blue in the textbook: (1) liquid oxygen is light blue; (2) When sulfur burns in the air, it has a faint light blue flame; (3) There is a light blue flame when hydrogen burns in air; (26) Three blue colors related to copper: (1) copper sulfate crystal; (2) copper hydroxide precipitation; (3) copper sulfate solution. 27. The filtration operation has "triple inclination": (1) The lower end of the funnel is close to the inner wall of the beaker; (2) the end of the glass rod gently leans against the third layer of filter paper; (3) The edge of the beaker containing the liquid to be filtered is close to the glass frame for drainage. 28. Qifupa Electric Appliance consists of three parts: a spherical funnel, a container and an air duct. 29. The flame of alcohol lamp is divided into three parts: external flame, internal flame and flame core, of which the external flame has the highest temperature. 30. Medication and medication have the principle of "three noes": (1) unnecessary. (2) Don't put your nose to the mouth of the container to smell the smell of gas; (3) Don't taste the medicine. 3 1. Write the CuSO4 and state of the following substances. 5H2O): blue solid basic copper carbonate (copper rust): green solid black solid: carbon powder, copper oxide, manganese dioxide and ferroferric oxide white solid: anhydrous copper sulfate (CuSO4), potassium chlorate, potassium chloride, magnesium oxide, sodium chloride, calcium carbonate, sodium carbonate and zinc sulfate purple black: potassium permanganate light green solution: ferrous sulfate (FeSO4)32. Conditions for burning combustible materials. Make the temperature of combustible materials reach the ignition point. 33. Gases containing diatomic molecules: H2, oxygen, N2, chlorine, F234. Which part of the atomic structure determines the following points: ①. The types of elements are determined by the number of protons; ② The classification of elements is determined by the number of outermost electrons; ③ The chemical properties of elements are determined by the number of outermost electrons; ④ The valence of elements is determined by the number of outermost electrons; ⑤ Organic compounds studied: CH4 (methane), C2H5OH (alcohol, ethanol), CH3OH (methanol), CH3COOH (acetic acid, acetic acid) 36. Macroscopically and microscopically, the law of conservation of mass can be summarized as five invariants, two definite changes, and one possible change: (1) Five invariants: macroscopically understanding the types of elements. (2) Two certain changes: recognizing that the types of substances must change from a macro perspective, and the types of molecules must change from a micro perspective; (3) A possible change: the sum of molecules may change. 37. Two simple substances of carbon: graphite and diamond (formation reason: different arrangement of carbon atoms). 38. Write down the following.

3. Some chemistry knowledge in life

1. Use of iodized salt.

Iodine is an essential nutrient for human body, and long-term iodine deficiency will lead to iodine deficiency. Edible iodized salt is the simplest, economical and effective method to eliminate iodine deficiency. Iodized salt contains sodium chloride and potassium iodate, which provides iodine for human body. Potassium iodate is unstable and easy to decompose when heated and illuminated, thus affecting the human body's iodine intake. So pay attention when cooking: add salt as soon as you cook it, and don't stew it for too long.

2. Don't cook tofu with spinach. Calcium oxalate is a precipitate that the human body cannot absorb.

Spinach, onion and bamboo shoots are rich in oxalic acid and sodium oxalate, and tofu contains more calcium salts, such as calcium sulfate. The above substances can undergo a metathesis reaction to generate calcium oxalate precipitation and other substances.

From a medical point of view: spinach, onions, bamboo shoots, etc. It is not suitable to mix with tofu at the same time, which will produce calcium oxalate precipitation, which is the cause of stones; From a nutritional point of view, mixed eating will destroy their nutrients. 3. The harm of aluminum to human health.

Aluminum has always been considered as a non-toxic element, so aluminum drinking utensils, baking powder containing aluminum expansion agent and water purification agent are widely used. However, recent studies show that aluminum can disturb human metabolism and cause long-term and slow harm to human health, and its toxicity is slow and difficult to detect. However, once the toxic reaction of metabolic disorder occurs, the consequences will be serious.

To prevent aluminum poisoning, we should pay attention to (1) reducing the entry route of aluminum, such as eating less fried dough sticks, and avoiding aluminum hydroxide as much as possible in stomach drugs. (2) Eat less food packaged in aluminum products.

(3) Use aluminum products appropriately to avoid long-term contact between food or drinking water and aluminum products. 4. Why can fruit sober up? This is because fruits contain organic acids, for example, apples contain malic acid, oranges contain citric acid, and grapes contain tartaric acid. The main component of wine is ethanol, and organic acids can interact with ethanol to form esters, thus achieving the purpose of sobering up.

Similarly, vinegar can relieve alcoholism because it contains 3-5% acetic acid, which can react with ethanol to produce ethyl acetate. 5. It is not advisable to burn oil and smoke when cooking. When oil is at high temperature, polycyclic compounds are easily formed. Generally, vegetable oil contains more unsaturated fatty acids, which makes it easier to form polycyclic compounds. Experiments show that polycyclic compounds are easy to induce animal bladder cancer.

Generally, as long as the oil is boiled, the "internal heat" of the oil can be removed. 6. Why is there a "red tide" in seawater?

In recent years, a large area of red tide has appeared in China's Bohai Bay and other offshore areas, which is called "red tide". Red tide is not a tidal phenomenon, nor is it a current movement like Kuroshio, but a biological phenomenon of red plankton overgrowth in the ocean under certain conditions.

Why can plankton multiply in large numbers? It turns out that a large number of wastewater, waste residue and substances that enter the ocean through atmospheric exchange contain elements such as nitrogen and phosphorus, which are essential nutrients for plant growth. So a large number of plankton proliferated rapidly, making the sea wear "red clothes".

In order to prevent the red tide in the ocean, we should control the discharge of wastes containing nitrogen and phosphorus into the ocean, such as wastewater containing phosphorus washing powder, so as to maintain the ecological balance in the ocean. 7. pH of food.

Studies have found that eating more alkaline foods can keep blood weakly alkaline, reduce acid substances such as lactic acid and urea in blood, and prevent them from depositing on the blood vessel wall, thus softening blood vessels. Therefore, some people call alkaline food "a cleaner for blood and blood vessels". Generally speaking, rice, noodles, meat, fish and eggs are almost all acidic foods, while vegetables, fruits, milk, sweet potatoes, potatoes, bean products and aquatic products are all alkaline foods.

Pay attention to scientific diet, improve diet structure, strengthen physical exercise and develop good living habits, and arteriosclerosis is expected to be delayed and reversed. The pH of human body fluids is closely related to IQ level.

Within the allowable range of body fluid pH, people with high acidity have lower IQ, while people with high alkalinity have higher IQ. Scientists tested dozens of boys aged 6 to 13. The results show that the IQ of children with body fluid PH greater than 7.0 is higher 1 times than that of children with body fluid pH less than 7.0.

Some children with poor academic performance and low level of intellectual development are often acidic. 8. Sulfur dioxide in food.

Sulfur dioxide is a very important member of inorganic chemical preservatives. Sulfur dioxide has been used as a food additive for centuries, and the earliest record is that it was used to disinfect wine containers in Roman times.

Later, it was widely used in food, such as sulfur fumigation in the manufacture of dried fruits and preserved fruits; Preparation of sulfur dioxide sustained-release agent for fresh-keeping storage of grapes and other fruits. Sulfur dioxide can show many technical effects in food, which is generally called bleaching agent, because sulfur dioxide can react with colored substances to bleach food.

On the other hand, sulfur dioxide can reduce the activity of oxidase, thus inhibiting enzymatic browning. In short, because the application of sulfur dioxide can make dried fruits and preserved fruits have beautiful appearance, some people call it cosmetic additive.

Sulfur dioxide not only plays a cosmetic role, but also has many non-cosmetic functions such as anti-corrosion and anti-oxidation, which is necessary to maintain the nutritional value and quality of food. For a long time, people have thought that sulfur dioxide is harmless to human body, but since Baker et al. found in 198 1 that sulfite can induce asthma recurrence in some asthma patients, people have re-examined the safety of sulfur dioxide.

After a long-term toxicological study, people think that sulfite preparation is harmless to most people at the current dose. There are two other points to note: sulfite in food must reach a certain dose to cause allergies. Even people who are very sensitive to sulfite are not allergic to all foods treated with sulfite. From this point of view, sulfur dioxide is a relatively safe preservative.

9. Why does salt deliquesce? How to make it not deliquescent? Magnesium chloride is usually contained in salt. Magnesium chloride deliquesces in air.

In order to prevent salt deliquescence, salt can generally be put in a pot for dry frying. Magnesium chloride is completely hydrolyzed at high temperature to produce magnesium oxide (MgO), so it loses deliquescence.

Or purified salt, pure sodium chloride is not in the air.

4. Where is the chemistry in life?

Salt is salty and is usually used for seasoning or pickling fish, eggs and vegetables. It is the most widely used condiment and is known as the "king of all flavors". People should eat a certain amount of salt every day (6 grams to 15 grams of salt is enough for adults every day). One reason is to increase the taste, and the other is the need of human function. Na+ mainly exists in extracellular fluid. It is an important component to maintain osmotic pressure and volume of extracellular fluid. The salt concentration in animal blood is constant. Excessive loss or insufficient supply of salt will increase excitability, resulting in weakness and trembling, which will eventually lead to paralysis of animals' hind legs and even death. American scientist Taylor personally experienced the process of eating salt-free food. Sweating increased at first, appetite disappeared, and I felt very tired after 5 days. On day 8-9, he felt muscle pain and stiffness. Then there was insomnia and muscle twitching, because the situation was more serious and the experiment was forced to stop. Of course, if you eat too much salt, you will absorb the water in the cells back into the body fluid, which will make your body have a fever due to lack of water. The process of transforming nitrogen in the air into nitrogen-containing compounds that can be absorbed by plants is called nitrogen fixation. There are usually two kinds of nitrogen fixation in nature: one is that nitrogen oxides in the air produce nitric oxide when lightning strikes. Nitric oxide further combines with oxygen to produce nitrogen dioxide, which is absorbed by water and becomes nitric acid, and falls to the ground when it rains. Another method of nitrogen fixation is to use rhizobia of plants, which is a kind of bacteria that can form nodules on the roots of leguminous plants. Under natural conditions, it can transform nitrogen in the air into nitrogen-containing compounds for plants to use. This is the truth that "growing beans will not gain weight, but will gain weight in a few years". In fact, the process of processing fresh eggs into preserved eggs is a complex chemical process. The strong alkali (sodium hydroxide and potassium hydroxide) in the ash material permeates into the egg yolk and egg white from outside the eggshell, and reacts with protein in the egg yolk and egg white, so that protein decomposes and solidifies, and a small amount of hydrogen sulfide gas is released. At the same time, the infiltrated alkali further reacts with the amino acids decomposed by protein, and the crystals of the generated salt condense in the egg white in a beautiful shape. Like "pine flowers" blooming one after another, hydrogen sulfide gas reacts with minerals in egg yolk and egg white to generate various sulfides, so the colors of egg yolk and egg white change, the egg yolk is dark green, and the egg white is special tea green. Salt can shrink and peel preserved eggs, improve taste and prevent corrosion. The added lead can accelerate the ripening of preserved eggs, and the tannins and aromatic oil in tea can solidify and color protein, thus increasing the flavor of preserved eggs.

5. What are the common chemical knowledge in life?

1. Sweet potatoes that have been put for a long time always taste sweeter than newly dug sweet potatoes. In the process of storage, water participates in the hydrolysis reaction of starch in sweet potato, and the starch is hydrolyzed into sugar, which increases the sugar in sweet potato.

2. It is not advisable to burn oil and smoke when cooking.

Oil is easy to form polycyclic compounds at high temperature. Generally, vegetable oil contains a lot of unsaturated fatty acids, which makes it easier to form polycyclic compounds. Experiments show that polycyclic compounds are easy to induce animal bladder cancer. Generally, just boil the oil.

3. How to remove the bitterness of fish bile? Bile acid is the main component of bitterness in bile. Because it is insoluble in water, it is difficult to completely wash the bile that has penetrated into the fish with water. Sodium carbonate can react with bile acid, and the product is sodium cholate, which is easily soluble in water.

If the fish bile is broken, just put some baking soda powder on the fish with bile and rinse it with water later, and the bitterness can be eliminated. If the bile pollution area is large, fish can be soaked in dilute alkali solution for a while, and then washed, and the bitterness can be completely eliminated.

6. Common knowledge of chemistry in life

Why do mung beans turn black after being cooked in an iron pot? After apples and pears are cut with iron knives, their surfaces will also turn black.

This is because the cells of mung beans, apples, pears and various fruits all contain tannic acid, which can react with iron to produce black iron tannic acid. When mung beans are cooked in an iron pot, they will produce some black iron tannins, so they will turn black.

Sometimes, pears and persimmons will have some black spots on their skins even if they are not cut with an iron knife. This is because tannic acid molecules contain many phenolic hydrocarbon groups, which are very sensitive to light and are easily oxidized by oxygen in the air and become black oxides. Milk should not be cooked at high temperature for too long. Milk is rich in protein.

When heated, colloidal protein particles will change greatly. When the temperature of milk reached 60-62 degrees, slight dehydration began, and protein particles changed from sol state to gel state, resulting in precipitation.

Milk also contains unstable phosphate. When heated, acidic calcium phosphate becomes neutral calcium phosphate, which will also be precipitated in the form of insoluble precipitate.

In addition, when the milk is heated to about 100℃, the lactose in the milk begins to coke, which makes the milk have leg color and gradually decomposes into lactic acid, and at the same time produces a small amount of formic acid, which makes the milk sour. So don't boil the milk for too long.

7. Physical and chemical knowledge in life

Physical phenomenon: (1) When sitting in a fast-moving car, you will feel the feeling of throwing outward when turning, which is centrifugal phenomenon.

(2) The working principle of nail clippers, scissors and tweezers is lever. (3) People use tweezers, chopsticks, scissors, etc. (4) Passengers on the train cannot stop immediately after braking. (5) Use a heavy object to see if it is parallel to the wall during construction. (6) When the battery stops running, its second hand often stops at the position of "9" on the dial.

This is because the second hand is most hindered by the large torque at the "9" position. (7) Sometimes, when tap water is discharged from an adjacent faucet, it occasionally makes bursts of noise.

This is because the water pipe vibrates when the water rushes out of the tap. (8) The "combustion" of electric furnace means that electric energy is converted into internal energy without oxygen. Oxygen can only oxidize the electric furnace wire and shorten its service life. Chemical phenomenon: what should I do if bronze turns black? If left in the air for a long time, it will "rust".

Copper will be oxidized into black copper oxide in humid air, and the copper oxide on the surface of bronze will continue to react with carbon dioxide in the air to form a layer of green basic copper carbonate CuCO3 Cu(OH)2) 2. In addition, copper will react with hydrogen sulfide in the air to produce black copper sulfide.

Scrubbing a dark bronzed surface with cotton dipped in concentrated ammonia water will immediately shine. Because the surface of bronzes is scrubbed with concentrated ammonia water, copper oxide, basic copper carbonate and copper sulfide will be transformed into soluble cuprammonia complexes and removed.

Or scrub with acetic acid to convert the dirt on the surface into soluble copper acetate, but this effect is not as good as the former. After washing, wash the bronzes with clear water, and the bronzes will shine again. 2. How to blacken silverware The principle of blackening silverware is similar to that of bronzes, because silver reacts with hydrogen sulfide in the air to produce black silver sulfide (Ag2S).

In order to brighten the silverware, it is necessary to wash off the oil stain on the surface with washing powder, put it together with aluminum, put it in sodium carbonate solution, and cook it until the silverware returns to silvery white. After taking out the silverware and washing it with water, you can see that the silverware surface is as bright as new. The chemical equation of the reaction is as follows: 2al+3ag2s+6H2O = 6ag+2al (OH) 3+3H2S3. Adhesives for plastics and plexiglass plastic products often appear in daily life. What should I do if they are damaged? There are two kinds of plastic products, one is PVC, which is hard and brittle, and the other is polyethylene, which is relatively soft.

Plexiglass is polymerized from methyl methacrylate. The best solvent for PVC is tetrahydrofuran.

The solvent of plexiglass can be chloroform, dichloroethane and acetone. When bonding, plastic or plexiglass can be directly bonded with these solvents, or a small amount of plastic or plexiglass can be dissolved in solvents to make an adhesive with better effect.

Learn to paint the wall with lime, cold water will become hot. After the wall is painted with lime, it is not easy to dry, and the lime wall becomes harder and whiter. Why? When slaking lime, quicklime meets aquatic slaked lime, which is an exothermic reaction, so cold water will become hot. It is difficult to dry walls with lime, because hydrated lime [calcium hydroxide] reacts with carbon dioxide in the air to produce calcium carbonate and water.

There is little carbon dioxide in the air and the reaction is slow. In addition, the formation of water makes it more difficult for walls to dry. When painting walls, lime slurry is calcium hydroxide, which is soft, and calcium carbonate generated after reacting with carbon dioxide is hard and white, so when calcium hydroxide is completely changed into calcium carbonate, it is hard and white.

5. Why does ink precipitate? Ink is a kind of colloid. When the ink bottle cap is not covered, with the evaporation of water, the ink thickens and the pigment colloidal particles are easy to squeeze together. Because the water layer between them becomes thinner, the colloidal particles will combine into large particles and precipitate.

In addition, the mixed use of different brands of ink will also lead to ink precipitation. Because colloidal particles are charged in order to stabilize them, inks made by different methods may have the same or different charges.

When the inks with different charges in the colloidal particles are mixed, the charges disappear due to neutralization, and the colloidal particles become unstable and precipitate. Knowing this, it is best to wash the pen with clean water when changing other brands of ink. In addition, supercooling and overheating will also destroy the colloidal solution in ink, leading to precipitation.

Therefore, the ink should be placed by the window in winter, not at high temperature in normal times. 6. Why can alum be used to purify water? Our ancestors used alum to purify water long ago.

The water treated with alum can remove 70-90% of suspended solids and bacteria. There are many tiny colloidal particles in suspended solids in water, and clay particles can adsorb anions and be negatively charged. After adding alum to water, positive trivalent aluminum ions neutralize the negative charge of clay particles, which makes them unstable and precipitate, and the water becomes clear.

7. The source of "scale" and the kettle that has been used for a long time have a layer of grayish yellow sediment on the boiler wall. Where did it come from? As we know, there are many inorganic salts such as calcium bicarbonate, magnesium bicarbonate and a small amount of calcium magnesium salts such as calcium sulfate and calcium chloride dissolved in water. When bicarbonate is heated, it is easy to decompose into carbon dioxide and carbonate, and carbon dioxide escapes into the air, while calcium carbonate is insoluble in water, and magnesium carbonate is slightly soluble in water, so it precipitates out, and the kettle and boiler that have been used for a long time have "scale".

Scale has poor thermal conductivity. Boiling water with kettles and boilers containing "scale" will cause energy waste. For factory boilers, when the "scale" is thick, it will automatically peel off a part, and uneven heating of each part will also cause an explosion. To remove the "scale", you can scrub it with very dilute hydrochloric acid and acetic acid, then immediately pour out the acid solution and rinse it with clear water.

8. Is the moisturizing effect of glycerol absolute? As we all know, pearl cream contains glycerin, and the function of glycerin is to absorb moisture in the air and keep the skin moist. So can pure glycerin be directly applied to the skin to moisturize? No, because if pure glycerin is directly applied to the skin, it can not only absorb the moisture in the air, but also absorb the moisture in the skin tissue. Strong fruit will make the skin drier and even burn. So when you buy glycerin, you must first ask whether it is pure glycerin or water-based glycerin. If it is pure glycerin, be sure to add 20% water to moisturize the skin.

9. Why does the fruit turn black after the iron knife is cut? Fruit contains more or less an organic compound tannic acid, which will change when it meets iron or other heavy metals.