Xiao Xiang wrote out some communication materials while learning density, among which the incorrect

Answer: a. Density is a characteristic of matter, and the density of different substances in the same state is generally not equal This statement is correct, so it does not conform to the topic

b. If the gas is in a closed container, the volume remains the same, the mass decreases, and the density will definitely decrease, so the statement is wrong and in line with the topic

c. According to the density formula = m

v It can be seen that the density of a solid object composed of the same substance remains constant in the same state, so the mass is proportional to its volume, so this item does not conform to the topic

d. According to the density formula = m

v It can be seen that the density of the substance with the same mass and the larger volume is smaller, so this item does not meet the meaning of the topic, so B is chosen

Choose a BA pair, for example, the density of liquid water and liquid oil is obviously different, and the oil floats on the water.

For example, the container contains candle oil (liquid), and when a part of it is removed, the candle solidifies, shrinks in size, and becomes denser.

When the state of matter is constant, the density is basically unchanged, so p is a fixed value, so v increases, and m also increases, so it is proportional.

When the mass is constant, the larger the density, the smaller the volume, and the smaller the volume, the greater the density.

If it helps, thank you, please ask if you don't understand.

Choose B, the quality of the oxygen cylinder has changed, but the volume of the oxygen cylinder is still so large, you can only know that it has become heavier, but its volume does not change (think about it, it is made of steel, and it is not like a balloon) The gas can be compressed. Density is mass divided by volume, and density has changed. So, choose B.

There may be a mistake, so please refer to it with caution. Don't worry, I'm definitely not plagiarizing)

Select c A solid object composed of the same substance does not necessarily have a mass proportional to its volume in the same state.

After a portion of the oxygen in the oxygen cylinder has been used. Will the density of the remaining oxygen in the cylinder change?

You should know the answer.

b. For example, the oxygen in the oxygen cylinder will become less dense when part of it is used.

b What is in the container, who knows what? Just pick it.

a. If the gas is in a closed container, the volume remains the same, the mass decreases, and the density will definitely decrease, so A is wrong;

b. Density is a characteristic of substances, and the density of different substances in the same state is generally not equal, so b is correct

c. According to the density formula = m

v It can be seen that when a solid object composed of the same kind of material is in the same state, the density remains the same, that is, the mass is proportional to its volume, so c is correct;

d. According to the density formula = m

v It can be seen that the density of a substance with equal mass and larger volume is smaller so d is correct;

So choose A

a. Density is a characteristic of matter, and the density of different substances in the same state is generally not equal This statement is correct, so it does not conform to the topic

b. If the gas is in a closed container, the volume remains the same, the mass decreases, and the density will definitely decrease.

c. According to the density formula = m

v It can be seen that the density of a solid object composed of the same substance remains constant in the same state, so the mass is proportional to its volume.

d. According to the density formula = m

v It can be seen that the density of the substance with the same mass and the larger volume is smaller, so this item does not meet the meaning of the topic, so B is chosen

a. According to the fact that density is a property of matter, the density remains unchanged when a solid object composed of the same substance is in the same state

b. Density is a property of matter, after half of a piece of chalk is used, its mass decreases, and the density does not change This statement is wrong, so it does not conform to the topic

c. If the gas is in a closed container, the volume remains the same, the mass decreases, and the density will definitely decrease, so the statement is correct and in line with the topic

d. The density of iron is greater than that of aluminum, which means that under the same volume, the mass of iron must be greater than the mass of aluminum, so this item does not meet the topic

Therefore, C

C. Analysis: Density is a property of matter, which has nothing to do with mass and volume. When half of a piece of chalk is used, its mass decreases and its density does not change. The mass of a dense substance is not necessarily large.

a From =m v, it can be seen that the density is directly proportional to the mass of the object and inversely proportional to the volume of the object It is not in the right place;

b After half of a piece of chalk is used, its mass decreases, and its density also decreases.

c. After using up a part of the oxygen next to the source in a cylinder, the mass of the remaining oxygen decreases, and the density also decreases, which is in line with the topic;

d The density of iron is greater than that of aluminum, indicating that the mass of iron must be greater than that of aluminum.

Therefore, CComments: Density is a property of matter, independent of mass and volume. When half of a piece of chalk is used, its mass decreases and its density does not change. The mass of a dense substance is not necessarily large. Understanding the concept of density is the key to solving this problem.