Chemistry in junior high school, very mentally retarded, but I m not sure

This sentence is true **The essence is pressure When the pressure of the gas is so strong that the wall can not bear it, it is a rupture If the gap between the air pressure and the maximum pressure is greater, the greater the power of the ** general** refers to the relatively large power But the essence of the balloon is the same Only the energy level is different How does the pressure difference occur? There are two methods, one is a chemical method Such as combustion, which produces gas and exothermy, and the heat will expand the volume of the gas so that the gas pressure will increase Of course, the general ** is to release a large amount of heat in an instant There are also physical methods to directly pressurize it As the balloon said upstairs The more air is blown in, the greater the pressure Can't bear it, the balloon bursts Of course, this energy is also very small But if you add 100 million megapascals to a house in an instant, the house will definitely not be able to withstand it, so it will be washed away by the gas And then some of the debris hits the gas at high velocity, and it's dangerous

You don't have to have a spark or a point, wouldn't a balloon burst if you shoot it hard?

Chemical changes may occur, physical changes may occur.

This is of course a physical change, do you think the balloon has new material produced at the time of **?

**There are physical changes, there are also chemical changes, and the chemical changes are usually the kind that need to be ignited, such as bombs** or something, and physical, such as balloons**, hehe

However, physical can also cause, for example, like the example you gave, for example, some combustible gases are compressed sharply in a certain space, and the pressure rises rapidly and the heat generated cannot be quickly discharged, resulting in a rapid rise in temperature, and after reaching the ignition point of the gas, it will occur, which is caused by physical changes, and it also has chemical changes, right?

The squad leader was right. A mixture of hydrogen and chlorine can be irradiated by the light emitted by the combustion of the magnesium belt**.

That's right, the essence of ** is because of the rapid diffusion of gases. Caused by chemical changes** is also caused by the instantaneous production of a large amount of gas to explode, or a balloon** is not a chemical change.

That's right. It is true that chemical changes can cause objects, but physical changes can also cause them. For example, if an object does work violently in a limited space, it will also cause **, and there is no chemical change in the middle, which belongs to the change in the house.

Even physical changes can cause **.

Your squad leader is right.

**The flame effect is due to the presence of flammable materials around, not the ignition of the flame itself, etc.

Have you ever played with a cannon (or a cannon)?

Does it need to be lit?

The squad leader said"Chemical or physical changes"Hm.

There is to have Mars. But I think there are both chemical and physical changes... The gas expands due to the increase in temperature, and in a certain space, the pressure increases, and it will... ** A chemical reaction occurs to generate new substances.

Nothing wrong.

1) Metathesis reaction.

2) Meet one of the conditions for the occurrence of metathesis reaction: precipitation is generated.

3) There is no solute NaOH in solution B. (Analysis: The filtrate is light blue, indicating that the copper sulfate is excessive and the NAOH is depleted.) )

1.Learn to judge the acid-base salts first.

2.Have a deep understanding of the definition and characteristics of metathesis reactions, and learn to write equation 3Remember the respective chemical properties of acids and alkalis, and memorize them by heart.

4.Keep in mind the conditions under which the metathesis reaction takes place.

5.The solubility table is remembered and will be used flexibly in the judgment of metathesis reactions and the writing of equations6Remember the anion and cation pairs that are capable of reacting.

7.Practice makes perfect.

All of the above must be strengthened and persevered on the basis of understanding.

Memorize a few more equations and you'll be fine.

If there are any questions, I will help you answer.

Most of the chemistry in the third year of junior high school is mainly based on memorization, as long as you grasp the definition first, you can judge the problem according to the definition, as for the calculation, it is based on your understanding of the definition, and the process of calculation is not very difficult!

Keep doing the questions. If you can't, ask the teacher, and don't give up, if you can't, you will definitely give up. Otherwise, it is impossible to learn badly. You bring me an example problem. I'll help you analyze it.

Wood has a way. "Knock" over and over again the questions you don't know. Most of them have to be understood, take your time, and memorize the key concepts and knowledge points.

When doing the question, draw more strokes, circle more, and write everything that can be written on the draft. I'm also in junior high school, and chemistry used to be terrible, so take your time. In fact, chemistry for the high school entrance examination is very simple, so don't be afraid.

Fry cold rice every day on the third day of the new year, and you will eventually figure it out, so don't give up, have faith!

Chemistry in the third year of junior high school is the foundation, you must read the book carefully, a lot of it is memorized knowledge, and the equations must be memorized.

Some methods must be mastered, not only when doing the question, often to understand that kind of question, now do not know the best place to ask the teacher or discuss with classmates, do not be confused in the past, do not understand must understand, otherwise it will drag on more and more, I wish you can learn better.

solutions, acids. Alkali, salt, these chapters need to understand the memory, to remember more of those are precipitation, for example, when you mention caCO3, you should immediately think of precipitation, and heating will decompose into cao and CO2. There are very few solutions used in junior high school, so it would be good if you memorized the properties of those that are often used and used more.

Salt: The positive part is a metal ion, and the negative part is an acid ion. The positive valence part of the acid is hydrogen. The base is hydroxide.

You can only read the book by yourself and review it slowly.

Either go to a teacher or sign up for a cram school.

If you don't bother, tell me the question, and I'll help you solve it, and you'll understand it yourself.

The main thing in this chapter is the chemical formula.

I remember that there is a theorem: only the formation of gas, precipitation, and what else can be carried out in the reaction, so when doing this kind of problem, first divide each compound into ionic form, and then combine to see if the above three can be generated, if so, it means that the reaction can be carried out, and then balanced.

Then it's pretty simple.

Write its m and m under the molecular formula of each compound, and then compare it, and the gas does not account for the mass fraction of the solution.

There are only a few types of compound reactions, memorize the concept of each one, and then see what examples of each one are, and just look at them and make a summary.

Chemistry in junior high school is very simple, in fact, practice makes perfect.

I haven't watched it in 10 years, I don't remember it very clearly, that's all.

In these three chapters, it's good to get the acid and alkali salts.