Scientific rumor-busting | The chemistry in fireworks and firecrackers

General Secretary Xi Jinping pointed out: "Scientific and technological innovation and popularization of science are the two wings for achieving innovative development. We must place popularization of science on an equal footing with scientific and technological innovation. Without a general improvement in the scientific literacy of the entire population, it will be difficult to build a large army of high-quality innovators and to achieve rapid transformation of scientific and technological achievements." Article 4 of Chapter 1 of the "Law of the People's Republic of China on the Popularization of Science and Technology" (hereinafter referred to as the Popular Science Law) states: "Popular science is a public welfare undertaking and an important part of the construction of socialist material and spiritual civilization. Developing the popular science undertaking is a long-term task of the state." Article 8 of Chapter 1 states: "Popular science work should adhere to the scientific spirit and oppose and resist pseudoscience."

The State Council issued the Outline of the National Science Literacy Action Plan (2021-2035) (hereinafter referred to as the Outline), planning to implement five science literacy improvement actions for young people, farmers, industrial workers, the elderly, leading cadres and civil servants during the 14th Five-Year Plan period. By 2025, the proportion of citizens with scientific literacy will exceed 15%, and by 2035, the proportion of citizens with scientific literacy will reach 25%.

Today we are going to talk about the chemical “rumors” about fireworks and firecrackers that we often encounter and hear in our daily lives!

Rumor 1: Fireworks are colorful because they contain colored substances.

Rumor 2: "Internet celebrity fireworks" are the safest fireworks

Let’s start with the origin of fireworks.

Fireworks originated from fireworks, and fireworks originated from gunpowder. my country is the hometown of gunpowder, and gunpowder is the evidence of ancient Chinese civilization. As early as more than 1,300 years ago, the famous medical scientist Sun Simiao recorded in detail the composition and properties of gunpowder at that time in "Alchemy Classics". It was not until the 14th century that gunpowder was introduced to Europe from India and Arabia, and Westerners began to know about gunpowder. According to historical books and related literary books, during the Sui and Tang Dynasties, gunpowder developed into fireworks for entertainment. Fireworks are also called fireworks and fireworks.

During the Xuanhe reign of the Northern Song Dynasty (119-1125), my country's fireworks made of gunpowder had already matured, with large-scale rack fireworks, such as "rack fireworks" and "bonsai fireworks". During the Ming and Qing dynasties, firecrackers and fireworks were already very popular among the people in my country. Every time there was a wedding, funeral, or festival, people would set off firecrackers and fireworks to express congratulations or pray to the gods and ancestors to bless the whole family and everything would go well.

By the way, the common saying about setting off fireworks and firecrackers to drive away the "Nian beast" is just a legend made up by modern people. You just have to listen to it!

Why are fireworks colorful?

Why are fireworks colored? Some say it's because of the pigments added? Or is there some chemical reaction that produces color? ... There are many explanations for the color of fireworks, which one should we believe?

After consulting the information, we learned that the chemical composition of fireworks and firecrackers can be roughly divided into four categories.

The first category is oxidants, such as nitrates, chlorates, etc.

The second category is combustible substances, such as sulfur, charcoal, magnesium powder and red phosphorus. The gunpowder in firecrackers is developed based on the black flame of 1 sulfur 2 nitrate 3 carbon. The explosion reaction after ignition is mainly:

The third category is flame colorants, such as barium salts, strontium salts, sodium salts and copper salts.

The fourth category is other special-effect drugs.

From the composition of fireworks, we know that the color of fireworks is determined by the flame coloring substances, which mainly refer to metal compounds.

The famous chemist Mr. Fu Ying once said: "Chemistry is an experimental science, and only experiments are the highest court." Therefore, we conducted a metal compound burning experiment and observed the color of the flame.

Through experimental research, we found that the color of the flame coloring substance (metal compound) itself has nothing to do with the color of the flame when burning. Therefore, the color of fireworks is the characteristic color of the flame when the metal compound burns, rather than the addition of colored substances. In chemistry, this process is called flame color reaction (or flame color test).

Flame color test of metals

Is this process a chemical reaction?

With such doubts, we consulted the People's Education Press's High School Chemistry Selection 2 and university textbooks, and truly realized the colorful nature of fireworks and firecrackers!

The generation of flame color is related to the change of electronic energy of metal atoms or ions, and does not involve changes in the structure or composition of the material. Therefore, the flame color reaction is only a physical change!

After seeing this, are many friends already eager to set off fireworks to see the colorful fireworks? Don’t worry, read the following first!

Why have many places issued clear notices banning the use of fireworks and firecrackers?

From the perspective of air pollution, setting off fireworks and firecrackers will release a lot of dust and air pollutants (including sulfur dioxide, nitrogen dioxide, nitric oxide, etc.), which will cause varying degrees of air pollution; from the perspective of noise pollution, the noise generated when firecrackers explode is around 100 decibels on average, and can reach over 120 decibels. According to research and analysis, the sound produced when setting off fireworks and firecrackers has far exceeded the ideal sound that humans can bear (15-40 decibels).

The process of setting off fireworks

We used the amount of substance in the chemical equation to quantitatively calculate the sulfur dioxide produced when fireworks are set off. From the calculation results, we know that: taking the fan-shaped flower pot as an example, we assume that every 4 people set off 20 fireworks per year, the mass of sulfur dioxide produced in Jiangsu Province alone is as high as about 1,030 tons per year, and the amount is as high as about 17,100 tons for the whole country. (Amazing numbers!!!)

But do you know?

On October 27, 2017, the World Health Organization's International Agency for Research on Cancer published a preliminary list of carcinogens for reference, and sulfur dioxide was on the list of Class 3 carcinogens; in addition, the formation of acid rain is caused by the human emission of large amounts of acidic substances (such as sulfur dioxide and nitrogen dioxide) into the atmosphere.

Now, do you know why many places in our country have issued clear notices prohibiting the use of fireworks and firecrackers?

The rise of “Internet celebrity fireworks”

Recently, some unscrupulous merchants have taken the opportunity to sell "Internet celebrity fireworks" such as steel wool fireworks and fairy sticks under the pretext of reducing pollution from fireworks and firecrackers, claiming that these fireworks are the "safest fireworks." Have you ever bought and set off such "fireworks"?

Are such beautiful "fireworks" really the "safest fireworks" as the merchants claim? And how much do you know about these "Internet celebrity fireworks"?

What are Steel Wool Fireworks?

According to the information, steel wool is also steel fiber and steel wool. It is made of low-carbon steel into 0.125-0.189 mm filaments. Comparing the current national standards for low-carbon steel and reduced iron powder, it is found that the iron content of the two is very close, about 98~99.135%.

In order to verify the composition of steel wool, we also designed an experimental plan to prove that the main component of steel wool is iron (including reactions of steel wool with dilute hydrochloric acid, steel wool with copper sulfate solution, and steel wool burning in the air).

The experimental phenomena are summarized as follows:

Steel wool reacts with dilute hydrochloric acid to produce bubbles

Steel wool and water vapor generate flammable gas - hydrogen at high temperature

Steel wool reacts with copper sulfate solution, the blue color gradually fades, and red substances precipitate on the surface of the steel wool

Steel wool burns in the air with sparks flying everywhere

The above results can prove that the main component of steel wool is iron.

Therefore, "steel wool fireworks" do not contain any pyrotechnic agents and are not fireworks, but setting them off is extremely dangerous! Huang Chaxiang, chairman of the National Technical Committee for Standardization of Fireworks and Firecrackers, said that the flame and spark temperature of "steel wool fireworks" is extremely high, reaching over 2000℃.

What are cold fireworks?

Stage fountain fireworks, birthday fireworks, fairy wands, etc. are all "cold fireworks". Do you think that they are "small in size, small in flame, and less in smoke", so they are not fireworks and firecrackers, and they are safe to set off?

In fact, cold fireworks refer to a type of pyrotechnic material that produces bright silver sparks or sparks as the main effect, with less smoke and residue. Its main component is pyrotechnic agent. Since cold fireworks emit extremely bright white light when they are set off, giving people a "cold" feeling, it reminds people of "cold light sources" (such as fluorescent sticks) based on the fluorescent luminescence mechanism. Therefore, the scientific and technological personnel who developed this type of fireworks in the early days figuratively called it "cold light fireworks" or "cold fireworks", and it is also called "ice and fire fountains" abroad.

According to research, the main components of cold light fireworks currently produced in China are single-base drugs (the main component is nitrocellulose) and certain special metal materials, such as titanium powder, zirconium powder, etc. In principle, this type of fireworks will continue to produce exothermic chemical reactions when they are set off. The temperature at the nozzle of cold fireworks is as high as over 1000°C, and the spark temperature can generally reach 100~200°C. Some larger spark particles can reach over 500°C. These burning sparks carry very high energy and are dangerous to cause fires. In terms of the luminescence mechanism, the luminescence of cold fireworks is mainly a continuous spectrum based on thermal radiation, and there are very few linear spectra and band spectra, rather than cold light luminescence.

Therefore, the temperature of cold fireworks is not low when they are set off, especially the temperature near the firework nozzle and some larger spark particles is very high. They are flammable and explosive dangerous goods and pose great hidden dangers.

Related Policies

On February 16, 2021, the Office of the State Council's Work Safety Commission held a special meeting to deploy the investigation and crackdown on illegal and irregular activities involving the production, transportation and sales of cold light fireworks and "steel wool fireworks", and issued a notice to put forward requirements. The notice emphasized that all "steel wool fireworks" currently sold in physical stores and online platforms must be removed from the shelves and properly disposed of.

Let’s summarize

Rumor 1: Fireworks are colorful because they contain colored substances

Scientific knowledge: The colorful flames when fireworks are set off come from the flame color reaction of the metal elements in the coloring material, and the flame color reaction is a physical change.

Rumor 2: "Internet celebrity fireworks" are the safest fireworks

Scientific understanding: "Internet celebrity fireworks" include steel wool fireworks, cold fireworks, etc. Although steel wool does not belong to fireworks, it is extremely dangerous when set off; cold fireworks belong to fireworks, and their basic properties of being flammable and explosive dangerous goods have not changed!

Safety Tips

Safety tips for fireworks:

All fireworks should be set off outdoors

Stay away from prohibited areas stipulated by laws and regulations. Do not set off fireworks in places that do not meet safety conditions, such as stairways, alleys, high-voltage lines, grasslands, and forests. Generally, fireworks are lit with smoke or incense. After lighting, you should leave immediately to a safe place. In case of abnormal conditions, please do not approach the product immediately, generally wait for 15 minutes before handling it.

Never set off fireworks towards flammable objects or people.

How to deal with injuries caused by fireworks:

After an injury, the tissue temperature of the operation site must be quickly lowered, and treatment methods such as cold water washing and ice compresses must be used to reduce swelling and prevent further injury. Local disinfection should be performed after cold compresses. If there is any damage, you should go to a regular hospital for treatment as soon as possible. Injuries to the head, ears, eyes, nose, and face should not be taken lightly and should all be treated in the hospital to avoid delaying treatment.

Authors: Ding Yi, Nan Feicheng, Li Zhurui, Yang Xuerou, Gu Mingzhe, Tang Yifan, Wo Jianqiang

Note: Ding Yi is the instructor (Nanjing Normal University), and the other authors are all high school students of Nanjing Zhonghua Middle School.