Any substance has characteristics. And the main of the characteristics of any substance is weight, or rather, specific gravity, the ratio of the weight of a particular body to the volume occupied by this body. This indicator follows from the mechanical definition of matter. It is through him that we are making the transition to the sphere of qualitative definitions. Matter for us is no longer an amorphous mass, tending to its center of gravity. Well, for example - the Solar system - all its bodies are different in specific gravity (how to calculate the specific gravity is slightly lower), because they have their own weight and their volume. If we take separately our Earth and its shells (lithosphere, hydrosphere, atmosphere), it turns out that they also have their own specific gravity, different and individual.
In the same way, individual chemical elements have their own weight, only atomic. This is also an expression of specific gravity. By the way, there are only a few elements that can be presented in pure form, and all the rest are compounds, as a rule, stable and called simple substances. There are more than five hundred of them in the lithosphere of our planet, each with its own specific gravity. How to calculate the specific gravity? And in general, can this be done?
Sure. Right now, we’ll look at how to calculate the specific gravity. It is better to do this with specific examples, to make it clearer.
1. For example, you are the head of a woodworking workshop and want to know how to calculate the proportion of sales of specific goods or work material in this case. Should be known: the amount of sale of a particular product and the total volume. Suppose we have: type of product - board, revenue - 15500 (rub), specific weight - 81.6%; product type - timber, revenue - 30,000 (rub), specific weight 15.8%; product type - croaker, revenue - 190,000 (rub), specific gravity 2.6%. Total: revenue - 190,000, and specific gravity (total), respectively, 100%. How to calculate the specific gravity of the board? Divide 155,000 by 190,000 and multiply by one hundred. We get 81.6%. This is precisely the specific gravity of the board.
2. How to calculate the specific gravity of any substance?
For some reason, specific gravity is often confused with density, although the concepts are completely different. Specific gravity does not apply to physicochemical characteristics and differs from density as, say, mass versus weight.
2.1.) Density is the ratio of mass to volume, and specific gravity is the ratio of weight to volume, this formula can be represented as follows: γ = mg / V. And if density is the ratio of the mass of a given body to the volume of this body, then the formula for finding the specific gravity, respectively, can be written in the following form: γ = ρg.
2.2.) If you wish, you can find the specific gravity through volume and mass, or in an experimental way, by comparing the pressure values. Here the hydrostatic equation will be used: P = Po + γh. But this method is applicable only in the case when all measurable quantities are known without exception. In this case, the formula for finding the specific gravity will take the following form: γ = P-Po / h. This equation is usually used to describe the communicating vessels and their action. Based on the experimental data, the conclusion will be fair: each substance in the communicating vessels will have its own height and its own spreading rate along the walls of the vessel in which this substance is located.
2.3.) In order to calculate (calculate) the specific gravity, one can apply another formula (the strength of Archimedes). Remember school physics lessons? Perhaps only a few will answer in the affirmative. Therefore, we refresh the memory: the force of Archimedes is a pushing force . Let’s say a load is given that has a certain mass (we designate this load as “m”), which is kept on water. At this moment, two forces act on the load, the first - the force of gravity, and the second - Archimedes (the force is pushing, and the direction will be back to the vector mg). In the formula, the Archimedes force looks like this: Fapx = ρgV. Knowing that ρg is equal to the specific gravity, we obtain the following equation: Fapx = yV, and from this we derive: y = Fapx / V.
Complicated? Then simplify: in order to calculate the specific gravity, divide the weight by volume.