"Exploration - Density of Matter" Scale, Mass and Density of the Material World PPT Courseware 4

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"Exploration - Density of Matter" Scale, Mass and Density of the Material World PPT Courseware 4

1. Proportion question

Example 1 The density ratio of two substances A and B is 3:2, and the mass ratio is 2:1. Find the ratio of their volumes.

analyze

This is a question about finding proportions. First, the density formula is deformed to obtain the expression for volume, and then the expression for volume ratio is listed. After simplification, the known ratio is substituted to solve the problem.

2. Smart measurements

Example 2 The mass of an empty bottle is 0.2kg. After filling it with water, the total mass is 1.0kg. After pouring out the water and filling it with another liquid, the total mass is 1.64kg. Find the density of this liquid.

analyze

The density of the liquid is calculated by the ratio of its mass to its volume. Its mass is equal to the total mass of the liquid and the bottle minus the mass of the bottle. Its volume is equal to the volume of the bottle, which is also equal to the volume of water. The volume of water is equal to water. The mass is divided by the density of water, which is equal to the total mass of water and bottle minus the mass of the bottle.

Example 3 In order to determine the density of a certain small steel ball, first fill an empty bottle with water and measure the total mass to be 540g. Then put a small steel ball with a mass of 97.5g into the bottle. After a part of the water overflows, Then measure its total mass to be 625g. Find the density of this small steel ball.

analyze

Because the mass of the steel ball has been given in the question, the density of the steel ball is required. The key is to find the volume of the small steel ball. The volume of the small steel ball is equal to the volume of water displaced by the steel ball. It only requires the mass of water discharged by the steel ball, and the volume of water can be calculated using the density deformation formula. The mass of the discharged water can be calculated as follows: subtract the total mass of the remaining water and the bottle from the total mass of the original full bottle of water and the bottle.

6. Experiment to measure density

Example 10 In order to determine the density of a solid with irregular shape and density smaller than water, a student designed the following experimental steps:

(a) Use a measuring cylinder to measure a certain amount of water;

(b) Read the volume v1 of water

(c) Use a balance to measure the mass m1 of the solid

(d) Tie an iron block with a string, tie the solid to be measured above it, immerse only the iron block in the water, and read the scale v2 of the water surface at this time.

(e) Use a balance to measure the mass of the iron block m2

(f) Then immerse the solid and the iron block in the water, and read the scale v3 of the water surface at this time.

Select the necessary steps in the above experimental steps and arrange them in the correct order.

analyze

This is a question that requires high experimental theory. Only by clarifying the experimental principles (formulas) and knowing what physical quantities must be measured can this question be answered correctly. The principle of measuring the density of matter is the formula ρ=m/v, so measuring solid

The step of measuring the mass m1 of the body is necessary, but the step of measuring the mass of the iron block is unnecessary. Because V3 in the title is the total volume of water, iron and the solid being measured, and V2 is the total volume of water and iron, then the volume of the solid being measured is V=V3-V2, so there is no need to measure the volume V1 of water.

Answer

The correct ordering of the necessary steps is (c) (a) (d) (f).

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Update Time: 2024-11-24

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