What are the ways to measure the density of solids?

There are many methods to measure the density of solids, and each method has its advantages and limitations. In practical application, the appropriate measurement method should be selected according to the characteristics of the measured object, experimental conditions and required accuracy. At the same time, in order to obtain more accurate measurement results, we need to pay attention to the standardization and accuracy of experimental operation. The following are some common methods for measuring the density of solids:

1. Direct measurement method

-Mass-volume method: This is the most basic method to measure the density of solids. Firstly, the mass m of the solid is accurately measured by a balance, and then a suitable measuring cylinder or cup is selected, and the volume v of the solid is measured by the drainage method. For solids with regular shapes, the volume can also be calculated by measuring their geometric dimensions (such as length, width and height) and using mathematical formulas. Finally, the density of solid is calculated according to the density formula ρ = m/v.

-Suspended wire method: suspend the solid to be measured with thin wires, measure its gravity f in the air first, then immerse it in a liquid with known density, and measure the gravity f at this time. According to Archimedes' principle, the buoyancy of a solid is F float = F₁-F₂, and the buoyancy is equal to the gravity that displaces the liquid, that is, F float =G row = gV row of ρ liquid, and V row =(F₁-F₂)/(ρ liquid G) can be obtained through deformation. Because the solid is submerged, V object =V row, and then the density of the solid can be calculated according to the density formula ρ matter =m/v matter = m/(F₁-F₂)/(ρ liquid g).

2. Indirect measurement method

-Buoyancy method: If the density of solid is less than that of water, the method of "floating to measure mass and sinking to measure volume" can be adopted. Firstly, the solid is put into water to float on the water surface, and the volume V row 1 of the boiled water of the solid is measured. According to the floating conditions, the gravity of the solid is equal to the buoyancy it receives, that is, G=F floating 1=ρ water gV row 1, so that the mass m of the solid is equal to ρ water V row 1. Then press the solid into the water with a thin iron wire to immerse it, and measure the volume of the boiled water discharged by the solid at this time, and the volume of the solid, V =V, 2. Finally, according to the density formula, calculate the density of solid ρ matter =m/V matter = ρ water v row 1/V row 2.

-Equal volume method: when there is no measuring cylinder or cup, you can use a balance to weigh the mass M of liquid with the same volume as the solid and known density. According to the density formula ρ liquid =m liquid /V liquid, you can get the volume V of liquid. Because the solid and liquid are equal in volume, V =V liquid, and then weigh the mass M of the solid, you can calculate the density of the solid according to the density formula.

3. Measurement method of special-shaped objects

-Sheet-like objects: For very thin objects, such as metal foil and plastic film, you can stack several identical sheets together, measure the total thickness hTotal, and then count the number n of sheets, then the thickness of a single sheet is h = hTotal/n.. When the total mass of multiple slices is measured by a balance, the mass of a single slice is m=m/n. According to the area S and thickness H of the slice, the volume V=Sh of the single slice can be calculated, and finally the density ρ=m/V=m/(Sh) of the single slice can be calculated according to the density formula.

-Granular objects: For granular objects, such as sand, salt, etc., you can first put the granular objects into a container with a known volume V and let them naturally pile up, and measure the total mass m of the container and the granular objects at this time. Then a part of the granular objects in the container is taken out, and the total mass m of the remaining part and the container is measured again, and the mass m=m₁-m₂ of the taken-out part can be obtained by the difference between the two masses. Since the ratio of the volume of some granular objects taken out to the volume of the remaining granular objects in the original container is equal to the ratio of their mass, that is, V/V₀=(m₁-m₂)/m₁, the volume of some granular objects taken out can be calculated as V=(m₁-m₂)V₀/m₁. Finally, calculate the density ρ=m/V=[(m₁-m₂)V₀]/[(m₁-m₂)V₀/m₁] of granular objects according to the density formula.