Impressions of chemistry. No less than 300 words

I think that the concept of chemistry is like a knife with two edges, good and bad, depending on whether it is used appropriately or not. For a period of time, there have been the following incidents in the society**: milk powder containing melamine, food bleached with excessive sulfur dioxide, formaldehyde preservation of seafood, etc., this aspect can be regarded as the harm brought by chemistry, but think about it deeply, more illegal businessmen deliberately do it for profit, it can be said that the social system is not perfect, the people's mind is not perfect, in my opinion, as long as the heart does not have different ideas, anything can develop in a good way, just like Nobel improved explosives, is not a good example?

Chemistry is everywhere in life, there are too many examples of it, I don't go into detail, just like the landlord said that new materials are used in clothing production, yesterday I just read a news about maternity clothes, and now many businesses on the market advertise their radiation-proof maternity clothes to protect radiation energy, and they also take out the certification results of relevant research institutions, but in fact they send to test the fabric rather than the finished product. This gives them a loophole and makes a huge profit. Moreover, sellers who do not understand chemistry confuse the concept and think that metal-containing fibers have strong radiation protection ability, which also misleads the majority of pregnant women.

The recent Shengyuan milk powder incident also touched me a lot, the specific ins and outs I think the landlord should have heard of it, I just want to say why children are precocious, parents will first think of milk powder problems? The melamine problem has cast a shadow over the vast number of people, so is there any concrete solution? Is it just a foreign thing?

It's a bit of a mess, but that's what I thought

My simple understanding of chemistry.

Chemistry is closely related to our lives,3 and we must study it well and explore it.

We can apply chemical principles to explain some of the most common phenomena in life, so that we can understand the world scientifically. For example, why do green plants have the effect of purifying the air?

Because it can photosynthesize under light, absorb carbon dioxide, and release oxygen.

We can use chemistry to improve our lives. Some chemical reactions that are unfavorable to us, we can try to prevent by applying chemical principles, and reactions that are favorable to us, can increase the rate at which they occur.

Chemistry can also make our lives more comfortable, for example, air conditioning in the hot summer, it plays a huge role, so, we to learn it, study it, explore it, apply it, as long as we observe it carefully, carefully experience, we will definitely feel its wonderful.

Chemistry is all about preparing for exams.

Hello! Chemistry is all about preparing for exams.

When in doubt, please ask.

Chemistry is a subject full of mysteries, and we can not only enrich our brains by studying chemistry, but also use it to solve some practical problems in life. Just like there are some white scales at the bottom of the pot where water is usually boiled, which is difficult to brush off, we can use the chemical method - vinegar soaking to get rid of it, and at the same time some cheongsam will be produced, which is because of the relationship between carbon dioxide production. As another example, I found that keys in the bathroom are prone to rust if a piece of paint falls off them, and we are used to saying that rust Fe2O3 is generated, but it contains complex chemical changes:

First, the copper on the outside of the key and the iron on the inside form a galvanic battery to generate some 2-valent iron ions and hydroxide to form ferrous hydroxide, which is oxidized into iron hydroxide, and then dehydrated to form rust. Not only that, some of the common changes in life usually refer to knowing some of the surface and knowing a little about the real causes, and the study of chemistry can give us a deep understanding of the principles of these phenomena, which allows us to benefit a lot.

Foreword: Candles are composed of paraffin wax and cotton wicks, and this experiment will observe the three stages of a candle before it is lit, when it is lit, and after it is extinguished. Subject & Discussion:

One. In general, it is solid, with different colors of candles, a slight pungent odor, a low melting point, a density less than water and insoluble in water. The candle we see burning is not the burning of a paraffin solid, but the ignition device that ignites the cotton wick.

Now the main raw material of candles is paraffin, paraffin is made from the wax-containing fraction of petroleum by cold pressing or solvent dewaxing, is a mixture of several higher alkanes, mainly n-dodosecane and n-octadecane, containing about 85 carbon elements and about 14 hydrogen elements. The added excipients are white oil, stearic acid, polyethylene, flavor, etc., among which stearic acid is mainly used to improve softness, and the specific addition depends on what kind of candle is produced. Two.

Carbon dioxide can make clarified lime water turbid. Carbon dioxide can make the clarified lime water turbid because the carbon dioxide reacts with the solute calcium hydroxide in the lime water to form calcium carbonate that is insoluble in water, that is, CO2 + Ca(OH)2 = CaCO3 + H2O. Experiment Report Experiment Name:

Candles and their combustion** Date of experiment: February 18, 2010 Purpose of experiment: **Nature and changes of candles Experimental instruments and medicines:

Candles, matches, glasses Experimental procedures and phenomena: 1Observe the appearance:

Candles are composed of paraffin wax and cotton wicks, colorless, solid, odorless, soft, low melting and boiling points, can burn, and have a lower density than water. 2.Light a candle:

1) The flame is divided into three layers, emitting black smoke, and the paraffin wax is melted by heat, glowing, and exothermic. Take a matchstick, hold one end and quickly put it flat into the flame, take it out after about 1 second, the middle of the matchstick is weak (white), and the two ends are strong (black). 2) Take a dry beaker and a beaker with clarified lime water to moisten the inner wall respectively, and cover the top of the candle flame successively, the inner wall of the dry beaker is black with small water droplets, and the clarified lime water on the inner wall of the beaker moistened with clarified lime water becomes turbid.

3.Candle extinguished: The candle is extinguished and white smoke is emitted.

Conclusions: 1Candles are solid.

2.The flame core temperature is the lowest, and it is not completely burned; The temperature of the outer flame is the highest (where the substance is heated); The internal flame temperature is low. 3.

Candles burn to produce water and carbon dioxide. 4.White smoke is paraffin vapor.

Experiment evaluation and discussion: This is a life experiment that is not difficult, does not require professional equipment, and can be done by everyone. The only thing it needs is a calm mind and careful observation, not deep theoretical knowledge or excellent experimental operation level, and it has a wide range of application prospects.

Through the candle and its burning **, my ability to extract knowledge and analyze problems has improved, which has made me more interested in chemistry. **。

Remember.