Ask something: Is it useful to do chemistry questions in junior high school? I took the test twice,

Useful, but not as effective as induction and summarization. After the exam, the key is to identify your own gaps so that you can fill them up and summarize them. If you do too many questions, you can't find your own problems, and you can't improve your score well.

Chemistry I'm average.

78 is better than me.

Doing test questions is a way for you to see some knowledge points that you haven't considered.

Let you see some problems that you didn't expect.

Do the question, see if you can really understand the question after you finish it.

It's just a matter of applying formulas to do questions.

Ah, there are definitely benefits to doing the questions. But you can't just know how to do the questions, that won't help much. To learn to summarize, by doing questions to see what to examine, slowly do more to know which knowledge point is important. Therefore, it is necessary to "be able to do questions".

Since I only started to get in touch with chemistry in the third year of junior high school, and junior high school chemistry is more than basic, so I usually have to memorize and summarize more, in fact, many of the test questions are very basic, and the form is only slightly changed. Of course, it is definitely beneficial to do more problems, for example, writing chemical equations, practice makes perfect. In addition to doing questions, you should also pay attention to analyzing the test papers to see which aspect you are more deficient in.

Yes. Chemistry in junior high school is a foundation. The score is not high. ，。But pave the way for what you have in high school.

The most important thing should be to listen to the class, listening well in class can solve many problems, and the main thing to do the questions is to understand the type of questions and increase proficiency, so as to prevent pressure caused by tight time during the exam.

Chemistry in junior high school is biased towards the basics, so just read more books to figure out the principles.

Chemistry in high school science is more difficult, and there are a lot of chemical formula formulas, so you have to do more questions at this time.

The concept must be understood, and then there is basically no problem in doing some problems!

Brushing questions must be useful, many people are brushing questions, but few people actually know how to brush questions.

First of all, you must know that brushing questions is not called brushing questions when you buy them yourself, from after-class exercises to exams, all the behavior of doing questions is a process of brushing questions.

Therefore, there is no such thing as a student who does not brush the questions, and the difference is only between quality and quantity. The subject also saw that many students had a small amount of questions, but they still learned well; There are also some students who have a lot of questions, but they still do a lot of tricks.

In fact, when you sweep your eyes, sometimes you won't find some details at all, such as the following paragraph:

The study of the table shows that the order of Chinese characters is not fixed. For example, when you read this sentence, you will find that all the words in this sentence are messed up. ”

If you simply swipe from left to right, you won't feel that there is anything wrong with this sentence, but when you go back and read this sentence carefully, you will find that this text is all messed up. Therefore, it is not reliable to scan the question with your eyes.

We all know that we should be slow and careful when reading and reviewing questions. At first, I thought that they were reading the questions too fast, so I repeatedly emphasized that the reading questions must be slow.

But then I found out that even though I took the rocks many times and reminded them, they consciously reminded themselves to be careful during the exam, but there were still cases of misreading and missing sights.

Here you have to know one thing: brushing questions is not an end, but a means. The core of brushing questions is to improve the knowledge network and build a knowledge system.

If you don't think about these problems, just being a problem-solver there, then you really can't do problems.

The process of really being able to do the problem is to perfect the four steps of reviewing the problem, translating the song, solving the problem, and checking.

Add 80 g of 15% NaOH solution with 15% NaOH solution reacted with CuSO.

80-40=40（g）

It contains NaOH 40 15%=6g, and the original CuSOs in the wastewater are X, and the Cu(OH) mass is Y, CuSO+2NaOH=Cu(OH) NaSO160 80 98

x 6g y

According to the proportional relationship, the solution is obtained.

x=12g,y=,The mass fraction of cuso is.

b is right, water vapor.

Lit sticks of wood or clarified lime water.

The first one is right.

The second is water vapor.

The third is to pass the gas produced after shaking the cola into the clear lime water, if the clarified lime water becomes turbid, it can be proved that carbon dioxide is produced, and the gas produced after shaking the cola is passed into the purple litmus solution, and the solution turns red.

bWater vapor.

d。[A is not true, because there are many gases that do not support combustion; c Not true, because after adding the clarified lime water to the cola drink, the change in lime water cannot be observed (the color of the cola is very dark); Both b and d are feasible, but d's operation of "passing the gas from a cola drink into clarified lime water" is simpler than d

It is a chemical reaction. The original deoxidizer only reacts with iron Fe and dilute sulfuric acid, so gas A should be hydrogen. The remaining mixture is sulfuric acid solution, ferrous sulfate solution, and activated carbon and NaCl.

Solid B is used in purified water", there is this sentence that can be associated with some substances of water purification, combined with the above question, it is realized that solid B must be activated carbon. Since the solids and liquids are separated, the first operation is filtration.

The test method of hydrogen, memorize the passage in the book without moving.

1.It is a chemical reaction because it is a reaction that is made up of multiple variations, that is, one substance is produced from two or more substances.

The answer should be (14*10%+1) (14+1).

According to the definition of the weight percentage concentration of the solution, if the solute is added to the solution, of course, the mass of the solute must be added to the numerator and denominator.

Mass fraction of sodium chloride = solute solvent.

After mixing, the amount of solvent is the sum of the two, and the weight of 1g of sodium chloride must be added. . .

The concentration of the solution = the mass of the solute (the mass of the solute + the mass of the solvent) x 100%.