Why does the glass break when it is scalded by boiling water

First of all, not all glasses will burst when exposed to hot water. But why do some glasses break?

In the past, when buying a glass, the salesperson would tell you whether it was a hot water cup or a cold water cup. The cold water cup is the one that will burst when it encounters hot water; And hot water cups will not. But the glasses I'm in now should all be hot water cups.

Especially in China, we all use glasses to make tea, so it's not a good thing that the glass can't touch the hot water. The maximum temperature of water at one atmospheric pressure is 100 degrees Celsius, and in our daily life, we will not have more than 100 degrees of water.

If thermal expansion and contraction were the only reason, all glasses should have burst when exposed to piping hot water. This is not the case. Therefore, heat expansion and cold contraction is part of the truth, in the process of manufacturing glasses, there is no proper treatment, and the glass is not manufactured correctly, which is also a very important reason.

As long as the heat expansion coefficient of the glass is relatively small, and the heat transfer coefficient is relatively large, so that the glass will not break. If you can temper the glass, it won't break.

Sharp heating of cold glass and rapid cooling of hot glass will cause breakage.

The principle of thermal expansion and cold contraction exceeds the tensile force between the molecular bonds of the glass, which is caused by the breaking of the molecular bonds.

1.Causes of glass cracks.

As the subject said, the reason for the broken glass is pouring hot water. The thermal expansion and contraction of objects is a universal law, and glass is no exception. Different materials have different effects of thermal expansion and contraction, which are usually expressed in terms of the coefficient of thermal expansion. The coefficient of thermal expansion of common materials is shown in the figure below.

The physical meaning of the coefficient of thermal expansion is a measure of the elongation of a material when the temperature increases by 1k. The higher this value, the more sensitive the material is to temperature. As you can see from the graph above, the coefficient of thermal expansion of ordinary glass is about k

Compared with some metals such as steel and copper, glass is a material that is not easy to expand and shrink in heat.

2. The location of the crack.

In fact, students who have studied physics in junior high school know that objects will expand with heat and shrink with cold, and cold glass is easy to burst after pouring hot water. However, if mechanics is not systematically studied, the mechanism should not be known. Thermal expansion and contraction are only general causes.

For this general reason, how does the glass expand, why do cracks occur, and cracks appear in **? Only by learning the mechanics of materials can it be possible to solve the problem.

Let's take a look at the circumferential and longitudinal thermal expansion and contraction, as shown in the figure above. The circumferential direction will be enlarged as a whole, and the longitudinal inner side will rise. Since the glass mouth is in a free state, the inside can be retracted freely, so it is difficult to produce longitudinal cracks.

But in the circumferential direction, the inner side temperature is high and I want to expand, and the outer side temperature is constant and I don't want to expand. Hence forcing the inside to swell and pushing the outside to expand. However, the internal measurement is always limited by the outer side, which is in a state of compressive stress, while the outer side is in a state of tensile stress due to the compression of the inner side.

The vast majority of materials in the world are compression- and tensile-resistant, with very different tensile and compressive properties. For example, plexiglass has a tensile strength of 55 77 MPa and a compressive strength of 130 MPa. It is precisely because of this unequal tensile and compressive properties that the outer glass cracks first.

3.How to prevent glass from breaking.

Knowing the above principles, we can prevent glass bursting from the following aspects:

1) Choose glass with higher quality. That is, choose a glass material with a small coefficient of thermal expansion to minimize the influence of temperature. With the improvement of glass manufacturing technology, the coefficient of thermal expansion has been much lower than that of the previous stage.

Unlike before, the glass is prone to bursting when hot water is poured. After design, even if the glass quality is slightly poor, as long as the thickness is sufficient, it is not easy to crack.

4.Summary. The glass burst is due to the uneven temperature in the direction of the thickness of the cup, resulting in an uneven distribution of thermal stress. The medial side is compressed, and the lateral side is compressed. The tensile ultimate stress of the glass is less than the compressive ultimate stress, so the outside cracks first.

This depends on the heat-resistant temperature of the glass. Some glasses can withstand temperatures of 100 degrees, while others can only withstand 60 degrees.

The reason why the glass bursts is because of the expansion, because as soon as hot water is poured into the cup, the inner wall of the cup will be heated and expand sharply, but because the outer wall remains the same, the inner glass suddenly squeezes outwards vigorously, so the cup breaks.

This is the principle of thermal expansion and cold contraction. Glass products cannot withstand high temperatures, otherwise they will expand and break.

When you pour hot water into the glass, the inner wall and the outer wall will not accept it to the same degree, which will cause a temperature difference, so there will be a force that will cause the glass to break.

Because glass is inherently a pressure-resistant material that does not resist tensile strength, and the thickness of the glass is uneven, the temperature distribution is uneven, which will cause the glass to break. It is recommended not to pour overheated water into the glass when drinking from a glass.

Why does the glass break when it is scalded by boiling waterDanliang, let's find out together.

When the glass is poured with hot water, it will cause the inner wall of the cup to be heated and expanded, but the speed of heat transfer to the outside is relatively slow, and the outside is less heated and less expanded, resulting in a force, and the glass will crack.

Some cups are not heat-treated, and when we pour boiling water into them, they cannot dissipate heat evenly immediately, and they are easy to crack.

The thinner the cup, the faster the heat conduction, and the temperature difference between the inner and outer walls is smaller, so it is not easy to break. In fact, pour boiling water slowly and in small amounts, and then shake the cup to heat evenly inside and outside the cup, which can well avoid bursting.

Expand: What are the common senses for the use of glasses

1. The newly bought glass should be soaked in cold salt water and boiled over a simmer to enhance the hardness of the glass and make it not easy to break. In addition, before pouring boiling water into the glass, put metal tableware into the glass, such as a steel or aluminum spoon, and then pour boiling water into the glass, the glass is not easy to break.

2. It is best to wash the glass every day and then dry it.

3. When cleaning the cup, not only the mouth of the cup, but also the inner wall of the glass should be cleaned, if it is not cleaned often, a lot of bacteria and dirt will be precipitated in it.

4. If the surface of the cup is too greasy, don't use dish soap, squeeze it on the toothbrush with toothpaste, and brush it back and forth on the quilt, which will remove dirt and not scratch the glass, killing two birds with one stone.

5. The used glass should be placed at any time to avoid collision and breakage.

What are the precautions for brewing green tea in a glass

1. Green tea should not be brewed too strongly, otherwise it will affect the secretion of gastric juice, and patients with high blood and heart disease are not suitable for drinking too strong tea.

2. Green tea is a cold tea, so it is best not to drink it when you are on an empty stomach, otherwise it is easy to cause diarrhea.

3. Don't drink the first brew of green tea, twist it and pour it out after brewing hot water, and then re-brew it with fresh boiling water before drinking.

4. When brewing green tea, the water temperature is controlled at about 80 90, if it is brewing green tea powder, it can be brewed with warm boiled water of about 40 60.

5. The brewed green tea should be drunk within 30 minutes and 60 minutes, otherwise the nutrients in the tea will become unstable.

That's all for today's sharing, I hope it can help you.

Summary. When the glass is scalded by hot water, the following steps need to be taken:1

3.Carefully remove the broken glass to avoid hand injury. 4.

Clean up broken glass shards and use items such as thick gloves or paper towels to protect your hands from scratches from the splinters. 5.Put the pieces in a plastic bag, seal it and put it in the trash can to avoid polluting the environment.

6.If needed, you can use a different container instead of a broken glass, but make sure that the container can withstand the temperature of the hot water. In short, when the glass is scalded by hot water, it needs to be stopped immediately and handled carefully to avoid causing harm to yourself and the environment.

When the glass is scalded by hot water, the following steps need to be taken:1Immediately stop using the glass, place it in a safe place, and avoid further use or touch.

Carefully remove the broken glass to avoid hand injury. 4.Clean up broken glass shards and use items such as thick gloves or paper towels to protect your hands from scratches by the shards.

5.Put the pieces in a plastic bag, seal it and put it in the trash can to avoid polluting the environment. 6.

If needed, you can use a different container instead of a broken glass, but make sure that the container can withstand the temperature of the hot water. In short, when the glass cup is scalded by hot water, it needs to be stopped immediately and handled carefully to avoid harm to yourself and the environment.

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Summary. If the glass is scalded by hot water, you need to pay attention to the following:1

Do not continue to use a cracked glass as it may break further and cause injury. 2.There may be hot water or hot liquid on the scalded glass, and if you need to dispose of it, you can wrap the cup in anti-scald gloves or a thick towel and carefully pour the liquid from the glass.

3.Be careful when cleaning up scalded glass shards to avoid cuts. Throw the pieces into the trash can with thick gloves or pliers, and wipe the ground around the pieces with a damp cloth to avoid splashing the glass shards.

If the glass is scalded by hot water, you need to pay attention to the following:1Do not continue to use a cracked glass as it may break further and cause injury.

2.There may be hot water or hot liquid on the scalded glass, so if you need to handle it, you can wrap the cup in anti-scald gloves or a thick towel and carefully pour out the liquid from the glass. 3.

Be careful when cleaning up the broken glass cup fragments to avoid being cut. You can use thick gloves or pliers to throw the debris into the trash, and then wipe the ground around the debris with a damp rag to avoid splashing the glass shards.

If the glass is scalded by hot water, you must first ensure your own safety, and then handle it carefully to avoid injury.

If the glass is scalded by hot water, it should be discontinued immediately and the broken glass shards should be handled carefully to avoid injury. If the hot water does not spill on other items, you can put the glass cup in a safe place to cool down, and then use a garbage bag or other container that can be isolated to fill the cup and debris and take it to the garbage dump for disposal. If hot water spills on other items, take care to dispose of other items to avoid injury.

Also, avoid using hot water to clean the glass again, and use warm water and a mild detergent to clean it.

The reason why the glass bursts is because of the swelling. As soon as hot water is poured into the cup, the inner wall of the cup expands sharply due to heat, but the outer wall of the cup remains the same, and the inner glass suddenly squeezes outward, and the cup breaks.

If you heat the inside and outside of the cup at the same time in advance, and then pour hot water, the degree of expansion between the inside and outside of the cup is not so large, and it will not burst. However, if the glass is very thin, even if hot water is poured into it, the heat will quickly spread to the outside, so that the inside and outside expand at the same time, and the cup will not break easily. In addition, the so-called hard glass and heat-resistant glass are not easy to burst because of the small proportion of expansion.

Therefore, remind everyone that when using the glass, you should first soak the cup in warm water, and then flush the boiling water, or pour a small amount of boiling water first, shake the glass to make the inner wall of the glass evenly heated, and then pour it full of boiling water, so that it is not easy to burst.