Interesting Multiple-choice Questions On Life Knowledge: Color-changing Mirrors, Fire Extinguishing, Why Food Is Sweeter?

There is a lot of interesting chemical knowledge hidden in life. Sometimes, a small and inconspicuous phenomenon contains a real chemical reaction.

For example, some people add a little vinegar when cooking, and the taste is particularly fragrant; some people roast sweet potatoes, but they always feel that they are not sweet enough. This is actually closely related to the changes in the ingredients in the ingredients.

The interesting multiple-choice chemistry questions that are common in daily life are organized below. See how many correct answers you can get, and you can also learn some practical scientific tips. What can't stump you?

Why do photochromic lenses change color?

When going out on a sunny day, the lenses of the photochromic glasses worn by many people will automatically darken. After entering the house, the lenses will turn back to transparent. The principle is actually not complicated.

Photochromic lenses are made by adding an appropriate amount of silver bromide and copper oxide microcrystals to ordinary glass.

When silver bromide encounters ultraviolet rays, it will decompose into silver atoms and bromine atoms. The silver atoms gather together, causing the lens to become darker. After reaching the room, the ultraviolet rays decrease, and the copper oxide helps the bromine atoms and silver atoms to combine again to form silver bromide, and the lens returns to transparency.

This reaction is reversible, so it can change color repeatedly.

If you wear photochromic glasses when driving, be aware that the car's front windshield blocks most of the ultraviolet rays, making the lens discoloration less noticeable.

Why do firefighters use yellow sand to extinguish magnesium powder fires?

Experienced firefighters, when encountering a magnesium powder fire, will not directly use water or carbon dioxide fire extinguishers to put out the fire, but will use a large amount of yellow sand to cover it.

Magnesium is an extremely reactive metal that can react with water at high temperatures to generate hydrogen. The burning of hydrogen will actually fuel the fire. Magnesium can also react with carbon dioxide to generate magnesium oxide and carbon, so ordinary fire extinguishers will not work on it.

The surface of the burning magnesium powder is covered with yellow sand. The yellow sand can quickly isolate the air. Without oxygen, the fire will naturally go out.

Generally speaking, in factories, dry and anhydrous yellow sand or fire extinguishing agents specially used to extinguish fires will be prepared at specific locations where active metals are stored. This is the reason behind it.

How soda ash helps digest greasy food

Many people will notice discomfort in their stomach after eating greasy food. The older generation likes to drink some alkaline water or eat pasta containing alkali, which makes sense.

Bile acids, which are responsible for emulsifying fat to aid digestion, are themselves insoluble in water and easily accumulate in the digestive tract.

Soda ash will react with bile acids, and the substance produced by the reaction is sodium bile acid. Sodium bile acid can be dissolved in water and can be smoothly excreted, thus reducing the greasy feeling that causes fullness and discomfort.

Of course, the soda ash here refers to edible alkali, not industrial soda ash.

On weekdays, when stewing meat or making pasta, adding a little bit of edible alkali can not only neutralize the sourness, but also make the taste smoother and more tender.

Why do sweet potatoes get sweeter after being stored for a long time?

The newly dug sweet potatoes do not taste very sweet. After being left for a period of time, the sweetness increases significantly. Many families have this experience.

During storage, the starch in sweet potatoes gradually undergoes hydrolysis under the action of amylase, thereby producing maltose and glucose.

Although the sweetness of maltose is not as sweet as sucrose, it is much sweeter than starch. Glucose itself is also sweet.

Adding water will evaporate slightly, and the relative concentration of sugar will be higher.

Therefore, we feel that sweet potatoes that have been stored for a long time are sweeter than newly dug sweet potatoes.

If you want the roasted sweet potatoes to be sweeter, then after buying them, place them in a cool and ventilated place for a week or two before roasting them. This will give you the most ideal effect.

The relationship between pencil lead hardness and clay ratio

Pencil lead is not pure graphite, but made of graphite mixed with a certain proportion of clay.

Graphite itself is very soft, and adding clay can increase its hardness.

If a large amount of clay is mixed in, the hardness of the pencil lead will increase, and the written words will be lighter in color, but not easy to break. If a small amount of clay is mixed in, and the proportion of graphite is high, the pencil lead will be soft, and the writing will be dark, but easy to break.

The hardness of the HB pencils used daily is moderate, the 2B pencils are softer and suitable for drawing and writing answer sheets, and the H series pencils are harder and suitable for drawing.

So the correct answer is: The more clay is mixed in, the harder the pencil lead becomes.

The difference in taste between copper ions and ferrous ions

Some metal ions do have unique flavors, which are related to their chemical properties.

Copper ions have a bitter taste, while ferrous ions have no taste.

Therefore, if you use a copper pot to boil water, or use copper utensils to hold acidic food, trace amounts of copper ions will be dissolved in the water or food, and the water or food will taste slightly bitter.

If the ferrous ions are dissolved with the vegetables in the wok, it will not change the taste of the vegetables, but it can supplement some iron elements.

However, it should be noted that excessive intake of copper ions will be harmful to the body. It is best to use copper tableware only to hold dry food, and not to hold acidic liquids for a long time.

Safety and anti-corrosion common sense in life

Fireworks are strictly prohibited in this area because flour particles floating in the air reaching a certain concentration will cause an explosion when exposed to an open flame. This is not an ordinary safety measure, but an extremely strict explosion prevention regulation.

Add a little pencil lead powder into the keyhole. Because graphite has a lubricating effect, the lock will be easier to open. This is a daily life tip.

Caustic soda is added to the fermented dough. Caustic soda is actually sodium hydroxide. It is extremely alkaline and can neutralize the acid produced by the fermentation of the dough. However, it is usually safer to use baking soda or edible alkali when making pasta at home.

It must be strictly controlled. Aluminum, which is identified as one of the sources of food contamination, is the metal aluminum used to make cans for carbonated drinks. Because carbonated drinks are acidic, aluminum ions will dissolve and enter the drinks.

As far as aluminum alloy is concerned, it is used to make doors and windows, used as a material for aircraft, and used to make wires. None of these have direct contact with food, so it is relatively safe.

These little knowledge about the chemistry of life may not be noticed at ordinary times. However, after knowing the principles behind it, it can not only increase your knowledge, but also play a role in your life.

Observe more and think more, chemistry is actually around us.