The following are chemical changes

Obviously, Ca is the irregular motion of molecules, B is the movement of the boat, and D is the change in the temperature of milk, all of which are physical changes.

CABC is essentially nothing new or pre-change, just a change in appearance. According to the definition of chemical change, it can be seen that the change in the formation of a new substance is called a chemical change, and d is a chemical change.

The third one is the creation of new matter, and the rest is just a physical change in the form, temperature, and state.

Only gasoline combustion is a chemical change.

Answer] D Answer Analysis] Test Question Analysis: The fundamental difference between physical change and chemical change is whether new substances are generated, and if new substances are generated, it is a chemical change; Otherwise, it is a physical change. Sucrose dissolution is a physical change in which sucrose changes from solid to liquid, and no new substances are generated. Dripping into ice is a physical change in which water changes from a liquid state to a liquid state, and no new substances are generated. The overflow of floral fragrance is diffusion, no new substances are generated, and it is a physical change; Iron rust is the process of iron reacting with water and oxygen to form rust at high altitude, forming new substances, which is a chemical change.

Therefore, the D test point is selected: the discrimination of chemical changes and physical changes.

Chemically, changes that produce other substances are called chemical changes. Chemical changes are characterized by the formation of other substances, often accompanied by color changes, precipitation, gas production, endothermy, exothermics, luminescence and other phenomena.

Chemical change refers to the change in various substances themselves. It can also be said to be the atomic rearrangement of the molecules of a substance under certain conditions.

See if it's a chemical change or if it's an object that changes into another substance.

Chemical change is relative to physical change.

In general, the creation of a new substance is a chemical change.

Chemical change does not refer to a change in what and what. Rather, when the substance changes, there is a change in the formation of a new substance, which is a chemical change. A substance changes, this substance may be a substance, such as calcined calcium carbonate, which can produce calcium oxide and carbon dioxide, and the reaction equation is:

CaCO3 = calcination = CO+CO2, this reaction is a reaction of two substances that are different from the reactants; Reactive substances may also be two, or two, or more. For example, when oxygen and hydrogen are ignited, water is formed, and the reaction equation is: 2H2+O2=2H2O, and this reaction is two substances that produce a reaction that is different from the reactants.

Which of the following changes is missing, and which one is not a chemical change? Carbon dioxide is produced during the combustion of the bas.

The water temperature is 0 degrees Celsius.

cWater and quicklime are mixed to produce a new substance.

dHoneycomb will produce carbon oxide containing Lingsheng Dili in the process of combustion.

Positive solution: B analysis: petroleum fractionation is the process of separating each component in petroleum into products (fractions) with different boiling point ranges by heating and evaporation by using the different boiling points of each component in the petroleum.

In other words, petroleum fractionation is a way of separating a mixture, which is a physical change.

The process of dry distillation of coal is a chemical change in which the coal is isolated from the air and the heat is strengthened to cause it to decompose.

Oil fractionation is a physical change that separates different components in petroleum according to the different boiling points.

The dry distillation of coal is the process of insulating the air and strengthening the heat of the coal to make it decompose, which involves a chemical reaction.

A petroleum fractionation physical change.

Dry distillation of coal chemical changes.

BA only separates a few mixed substances, while B needs to be cleaved into low-carbon chain substances.

Dry distillation is a chemical change that causes the coal components to undergo a decomposition reaction.

b Dry distillation is a chemical change A is a physical change.

It seems to be A. It appears that the design temperature change affects the reaction.

For a, there is the equation Na2CO3+10H2O=, and the condition of the second equation is weathering.

For b, because concentrated sulfuric acid is absorbent.

Yes C, because coarse salt is soluble in water, yes D, I don't need to explain.

The loss of crystalline water is also a chemical change, because the composition of the chemical formula of the substance with crystalline water and the substance without crystalline water has changed significantly, and the microstructure has changed even more.

B: The water absorption of concentrated sulfuric acid and the deliquescent of C crude salt are equivalent to a self-absorbed water dissolution phenomenon, and the dissolution is of course a physical change. CO2 is good at absorbing heat, and CO2 absorbs more heat, so when the temperature rises, of course there is no chemical reaction, just a physical change.

Hope it solves your doubts.

From Na2CO3 and water to two substances.

for a new substance is formed. Everything else is a physical change. It is necessary to distinguish between the definition of chemical change and physical change.

C bulbs emit light --- glow when heated to a certain temperature, and the physical changes.

The candle melts - the solid becomes liquid, the physical changes.

Select B AThe decolorization of brown sugar solution with charcoal is based on the adsorption of charcoal, and no new substances are generated.

b.Although graphite and diamond are both composed of c atoms, they are two different substances in different order of atoms.

c.Diamond carved glass changes physically, and no new substance is generated.

d.Pencil leads made from graphite powder mixed with clay are a mixture of two different substances and no new substances are formed.

Answer A analysis: chemical change refers to the change of the formation of new substances, physical change refers to the changes without the formation of new substances, and the essential difference between chemical changes and physical changes is whether new substances are formed; Judge according to this analysis

Answer: a. In the process of burning celery and setting off fireworks, new substances such as carbon dioxide are generated, which is a chemical change; Therefore, the option is correct

b. In the process of cutting glass, only the shape changes, and no new material is generated, which is a physical change; Therefore, the option is incorrect

c. Seawater salt drying is the use of sunlight and wind to evaporate water to obtain salt, no new substances are generated, which is a physical change; Therefore, the option is wrong

d. In the process of evaporation, only the state of alcohol changes, and no new substances are generated, which is a physical change; Therefore, the option is incorrect

Therefore, choose a Comment: This question is not very difficult, and the answer should be analyzed whether there is a new substance formed in the process of change, if there is no new substance, it is a physical change, and if there is a new substance, it is a chemical change