9th grade science questions, 9th grade first volume science questions

1.Do you have to memorize chemical equations and their phenomena.

Of course to back!

2.If you want to memorize whether there is a good memorization.

Yes. In fact, doing experiments on the computer or in the laboratory can be played and memorized.

Such memories are relatively easy to remember.

If it doesn't work yet. You're going to have to memorize it every day. Look at it every day.

Or when you communicate with your classmates after class, you can ask questions or make some jokes.

For example, some of my classmates. When he smells certain gases. will say it out loud. Who's putting carbon dioxide? etc.).

I think it's fun and easy to remember (my opinion.) As long as you listen carefully in class, you can quickly remember most of the numbers.

You'd better take a notebook (specializing in memorizing scientific knowledge) and write down the key points that the teacher says every day (as long as you think it's important; Because I'm stupid, I crossed out and copied everything the teacher wrote down or said

But it's still the same old saying: as long as you listen carefully in class. It's better than not listening to it, sorry. It's possible that you don't think it's much of a use, but I'll offer a way to do it.

The glomeruli have mechanical barriers and ionization barriers.

Normally, proteins are not filtered.

1) HCL2) solution: (25g-5g).

The Na2CO3 solution reacted with the calcium chloride solution to generate 5g of calcium carbonate precipitate: the mass of the solute in the 20GN2CO3 solution was XNa2CO3+CaCl2=

caco3↓+nacl

x5g106：100=x：5g

x = the mass fraction of the solute in the Na2CO3 solution is.

6*10 5 j (law of conservation of energy), less than (also converted to other energies, such as heat energy when turning).

First of all, from the fact that the precipitate can be completely dissolved and gas is generated, it can be inferred that the precipitate must be carbonate, which indicates that the original solid contains sodium carbonate.

Then it can react with sodium carbonate to form a precipitated substance of barium chloride. Because the precipitate is completely dissolved in dilute hydrochloric acid, sodium sulfate must not be present, otherwise the resulting barium sulfate cannot be dissolved in hydrochloric acid.

From the above, it is known that the white solid must have sodium carbonate, barium chloride; No sodium sulfate. As for sodium hydroxide, I still can't tell if it exists from the title, so choose A

Sampling is soluble in water, and white precipitate is produced This sentence can judge that the white items are not sodium hydroxide and sodium sulfate, sodium hydroxide is very soluble in aqueous solution and colorless, while sodium sulfate is insoluble in water!!

After filtration, hydrochloric acid is added dropwise to the white precipitate, and the precipitate is completely dissolved and gas is produced This sentence can determine that the white item is not barium chloride, because the reaction between barium chloride and hydrochloric acid does not produce gas!! So choose C!!

Sampling dissolved in water has a white precipitate produced", the precipitate may be barium sulfate, barium carbonate, barium hydroxide.

After filtration, hydrochloric acid is added dropwise to this white precipitate, and the precipitate is completely dissolved and gas is generated", excluding barium sulfate.

completely dissolved and gases produced". Then there must be barium carbonate, and barium hydroxide cannot be judged.

Therefore, there must be no sodium sulfate in the original white solid, sodium carbonate, barium chloride, and sodium hydroxide may be there.

Therefore, answer A is correct and BCD is wrong.

A (just checked, indeed A).

c. The environment that creates hypoxia is conducive to lactic acid fermentation.

c Renal tubules Question 2 Because acetic acid bacteria make vinegar. Kimchi requires lactic acid bacteria, and lactic acid bacteria fermentation requires an oxygen-free or oxygen-deficient environment, so water is poured into the kimchi jar to prevent air from entering.

Question 3 Inertia is only affected by mass and has nothing to do with velocity.

B first judge the ferric chloride by the color, the ferric chloride solution is brownish-yellow, the other three solutions are colorless, the ferric chloride solution is dropped into the remaining three solutions, there is a reddish-brown precipitate to produce a caustic soda solution, the caustic soda solution is dropped into the remaining two solutions respectively, there is a white precipitate to produce a magnesium nitrate solution, and the last one is a salt solution.

b Ferric chloride is yellow, and the others are colorless, which is the first to be identified.

Iron chloride can react with caustic soda to form a reddish-brown precipitate of iron hydroxide, and the identified caustic soda can react with magnesium nitrate to form a white precipitate of magnesium hydroxide.

First of all, it was seen that ferric chloride was yellow, and three samples of caustic soda were added to precipitate. After the reaction, iron hydroxide is added to two test tubes and reacts with magnesium nitrate to form a precipitate.

So choose B