por The microscopic scale It is one that is used to measure the sizes and lengths that cannot be seen with the naked eye and that are below a millimeter in length. From largest to smallest, the microscopic scales in the metric system are:
– The millimeter (1 mm), which is one tenth of a centimeter or one thousandth of a meter. On this scale we have one of the largest cells in the organism, which is the ovule, whose size is 1.5mm.
– The tenth of a millimeter (0.1 mm). This is the scale of the thickness or diameter of a human hair.
– The micrometer or micron (1μm = 0.001mm). On this scale are plant and animal cells and bacteria.
Plant cells are of the order of 100μm. Animal cells are ten times smaller, it is of the order of 10μm; while bacteria are 10 times smaller than animal cells and are of the order of 1μm.
[toc]
nanometer scale
There are measurements even smaller than the microscopic scale, but they are not commonly used except in a few special contexts. Next we will see some of the most important nanometric measurements:
– The nanometer (1 ηm = 0.001 μm = 0.000001 mm) is one millionth of a millimeter. On this scale are some viruses and molecules. Viruses are of the order of 10ηm and molecules of the order of 1ηm.
– The angstrom (1Å = 0.1ηm = 0.0001μm = 10-7mm). This measurement forms the scale or atomic size.
– The fantometer (1fm = 0.00001Å = 0.000001ηm = 10-12mm). This is the scale of atomic nuclei, which are between 10,000 and 100,000 times smaller than the atom. However, despite its small size, the nucleus concentrates 99.99% of the atomic mass.
– There are smaller scales than the atomic nucleus, since these are made up of particles such as protons and neutrons. But there is more: these particles are in turn made up of more fundamental particles such as quarks.
Instruments for microscopic observation
When objects are between the millimeter and micrometer scale (1mm – 0.001mm), they can be observed with an optical microscope.
However, if the objects or structures are between nanometers and Angstroms, then electron microscopes or the nanoscope will be required.
In electron microscopy, instead of light, high-energy electrons that have a wavelength much shorter than light are used. The disadvantage of the electron microscope is that it is not possible to place live samples in it because it works in a vacuum.
In contrast, the nanoscope uses laser light, and has the advantage over electron microscopy that structures and molecules within a living cell can be viewed and recorded.
Nanotechnology is the technology with which circuits, structures, parts and even motors are manufactured on scales ranging from the nanometer to the atomic scale.
microscopic properties
In physics, in a first approximation the behavior of matter and systems is studied from the macroscopic point of view. From this paradigm matter is an infinitely divisible continuum; and this point of view is valid and adequate for many situations of daily life.
However, some phenomena in the macroscopic world can only be explained if the microscopic properties of matter are taken into account.
In the microscopic point of view, the molecular and atomic structure of matter is taken into account. Unlike the macroscopic approach, at this scale there is a granular structure with voids and spaces between molecules, and even within atoms.
The other characteristic of the microscopic point of view in physics is that a piece of matter, no matter how small, is composed of an enormous number of particles separated from each other and in continuous movement.
-Matter is an immense void
In a small piece of matter the distance between atoms is enormous when compared to their size, but in turn the atoms are huge when compared to their own nuclei, where 99.99% of the mass is concentrated.
That is, a piece of matter on the microscopic scale is a huge vacuum with concentrations of atoms and nuclei occupying a tiny fraction of the total volume. In this sense, the microscopic scale is similar to the astronomical scale.
From macroscopic objects to the discovery of the atom
The first chemists, who were the alchemists, realized that materials could be of two types: pure or compound. Thus the idea of chemical elements was arrived at.
The first chemical elements discovered were the seven metals of antiquity: silver, gold, iron, lead, tin, copper, and mercury. Over time, more were discovered as substances were found that could not be broken down into others.
Then the elements were classified according to their properties and characteristics into metals and non-metals. All those that had similar properties and chemical affinity were grouped in the same column, and thus the periodic table of elements emerged.
From the elements he passed to the idea of atoms, a word that means indivisible. Soon after, scientists realized that atoms did have a structure. In addition, the atoms had two types of electrical charge (positive and negative).
subatomic particles
In Rutherford’s experiments in which he bombarded the atoms of a thin gold plate with alpha particles, the structure of the atom was revealed: a small positive nucleus surrounded by electrons.
Atoms continued to be bombarded with more and more energetic particles and are still being done, in order to unravel the secrets and properties of the microscopic world on an ever smaller scale.
In this way, the standard model was reached, in which it is established that the true elementary particles are those of which atoms are composed. In turn, atoms give rise to elements, these to compounds and all known interactions (except gravitation). In total there are 12 particles.
These fundamental particles also have their periodic table. There are two groups: fermionic spin ½ particles and bosonic particles. The bosonics are responsible for the interactions. There are 12 fermionics and they are the ones that give rise to protons, neutrons and atoms.
As count particles on a microscopic scale?
Over time, chemists discovered the relative masses of the elements from precise measurements in chemical reactions. Thus, for example, it could be determined that carbon is 12 times heavier than hydrogen.
Hydrogen was also determined to be the lightest element, so this element was assigned the relative mass 1.
On the other hand, chemists needed to know the number of particles involved in a reaction, so that no reagent was left over or missing. For example, a water molecule requires two hydrogen atoms and one oxygen.
From these antecedents the concept of mole is born. A mole of any substance is a fixed number of particles equal to its molecular or atomic mass in grams. Thus it was determined that 12 grams of carbon have the same number of particles as 1 gram of hydrogen. That number is known as Avogadro’s number: 6.02 x 10^23 particles.
-Example 1
Calculate how many gold atoms are in 1 gram of gold.
Solution
Gold is known to have an atomic weight of 197. This can be found on the periodic table and indicates that a gold atom is 197 times heavier than a hydrogen atom and 197/12 = 16,416 times heavier than carbon.
A mole of gold has 6.02 × 10^23 atoms and has the atomic weight expressed in grams, that is, 197 grams.
In a gram of gold there are 1/197 moles of gold, that is to say 6.02×10^23atoms/197 = 3.06 x10^23 gold atoms.
-Example 2
Determine the number of molecules of calcium carbonate (CaCO3) in 150 grams of this substance. Also tell how many calcium, how many carbon, and how many oxygen atoms are in this compound.
Solution
The first thing is to determine the molecular mass of calcium carbonate. The periodic table indicates that calcium has a molecular weight of 40 g/mol, carbon 12 g/mol, and oxygen 16 g/mol.
Then the molecular mass of (CaCO3) will be:
40 g/mol + 12 g/mol + 3 x 16 g/mol = 100 g/mol
Every 100 grams of calcium carbonate is 1 mol. So in 150 grams they correspond to 1.5 moles.
Each mole of carbonate has 6.02 x 10^23 carbonate molecules, so in 1.5 moles of carbonate there are 9.03 x 10^23 molecules.
Summarizing, in 150 grams of calcium carbonate there are:
– 9.03 x 10^23 calcium carbonate molecules.
– Calcium atoms: 9.03 x 10^23 .
– Also 9.03 x 10^23 carbon atoms
– Finally, 3 x 9.03 x 10^23 oxygen atoms = 27.09 x 10^23 oxygen atoms.
References
Applied biology. What are the microscopic measurements? Retrieved from: youtube.com
Chemistry education. Macroscopic, submicroscopic and symbolic representations of matter. Retrieved from: scielo.org.mx.
García A. Interactive physics course. Macrostates, microstates. temperature, entropy. Retrieved from: sc.ehu.es
The microscopic structure of matter. Recovered from: alipso.com
Wikipedia. Microscopic level. Retrieved from: wikipedia.com