Grade 9 Chemistry Questions, Ask Grade 9 Chemistry Questions

Lime water is a mixture, the other four are pure, and CO2 is pure.

It's easy to distinguish a mixture from a purity. A pure substance is a substance, and a mixture is a variety of substances. For example, lime water is obtained by Ca(OH)2 dissolved in water, so it is composed of two substances: Ca(OH)2 and water.

The easiest way to distinguish between a chemical formula is a pure substance, and a mixture if a chemical formula cannot be written. Also, remember that all solutions are mixtures.

The concept of two elements and two substances is different, potassium chloride is a substance composed of the element chlorine and potassium and is pure.

Ca(OH)2 is calcium hydroxide, which is lime water when dissolved in water. When writing the chemical equation, because water does not participate in the reaction, it is enough to write only Ca(OH)2, but Ca(OH)2 represents the pure substance calcium hydroxide.

When I asked during the exam, of course, copper wire is pure. If you also have to consider the problem of oxidation. A lot of pure things turned into mixtures in the air.

I know too much.

Bu Guo can memorize the periodic table.

It's very helpful for studying chemistry.

I feel like lime water and copper wire are both mixtures.

1|Lime water is quicklime plus water , which is made up of two substances, so it is a mixture.

2|Copper wire Generally, copper oxide will be on the surface of copper wire placed in the air, and copper plus copper oxide are also two substances, so it is also a mixture.

CO2 is a pure substance that can be composed of two elements, but it can form a new substance, which is a compound.

The last question itself is not true, pure substances include compounds, which means that if they are compounds, they must be pure, but pure substances can also be elemental.

A substance made up of two different atoms is a mixture.

CO2 is pure because it is written, because the chemical formula written in letters means that it is pure, and copper wire is actually pure, but it will oxidize, so it needs to be analyzed!

Lime water is a mixture because it is an aqueous solution of calcium hydroxide.

Pure substance A substance may be composed of different elements.

There are a lot of substances in the mixture, and it's easy to analyze the difference between substances and elements.

Summary. These three gases must be tested first, with anhydrous copper sulfate, then carbon dioxide, with clarified lime water, why not test carbon monoxide, because carbon monoxide will produce carbon dioxide, interference, and finally test carbon monoxide, through copper oxide, the carbon dioxide produced is tested with a sufficient amount of lime water, and at the same time use an alcohol lamp for carbon monoxide tail gas treatment.

The last empty teacher.

Okay, thank you, teacher.

Support. These three gases, must first test water, with anhydrous copper sulfate, then test carbon dioxide, with clarified lime water, why not test carbon monoxide, because the test of carbon monoxide will produce carbon dioxide, interference, and finally test carbon monoxide, through copper oxide, the carbon dioxide produced with a sufficient amount of lime water test, at the same time with alcohol lamp for carbon monoxide silver tail gas spike banquet treatment.

Wow ok thank you teacher! I see.

Okay, you're a lot better than others, it's not just the answers, giving you a thumbs up <>

1。The calcium hydroxide in the clarified lime water reacts with carbon dioxide in the air to generate calcium carbonate insoluble in water Ca(OH)2+CO2==CaCO3+H2O2 hydrogen oxygen decomposes to form hydrogen atoms and oxygen atoms, one oxygen atom and two hydrogen atoms combine to form a molecule of water, and many water molecules form water substances.

3 (1) Water molecules decompose into hydrogen and oxygen atoms, which in turn combine to form hydrogen and oxygen (2) The alcohol volatilizes without a lamp cap, and water is left on the wick, so it is difficult to ignite it the next time it is used. Alcohol and water are miscible with each other. The reason is that the alcohol molecules run into the voids of the water molecules.

3) The air in the bottle expands when heated, shrinks after cooling, the thermal movement decreases, the water vapor becomes liquid water, and there is a pressure difference between the inside and outside, so it cannot be opened.

The type of atom does not change before and after the chemical reaction).

P.S. Upstairs, you're 3 (2) wrong.