In 1869, the Russian chemist Dimitri Ivanovich Mendeleev introduced a new system for ordering the chemical elements. That is why, 150 years after its first public presentation, 2019 has been declared “International Year of the Periodic Table” Periodic Table of 1876.
In order to describe certain properties of matter, such as states of aggregation (solid, liquid and gas), boiling and melting temperatures, viscosity, solubility, density, etc., it is necessary to consider the forces that hold together the particles that make up each of the substances.
Before we start, let's review some concepts: The solutions are homogeneous mixtures (their properties and composition are uniform) of two or more substances. We call the substance found in the highest proportion: solvent , and the substance(s) found in the lowest proportion:
The lipids are part of a group of very different chemical compounds, but they have in common that they are soluble in organic solvents , such as ether, benzene and acetone, and insoluble in water . They are present in both animal and plant cells, and are, along with carbohydrates (carbohydrates), proteins and nucleic acids , one of the four most important groups of the so-calledbiomolecules.
It could be said that, when hearing the words “hache dos o”, most people immediately associate them with water. But what does this expression mean? What does it tell us about this substance? Does it tell us anything, for example about its structure?
Biological membranes are essential for life, marking cell boundaries and dividing cells into separate compartments. In addition, they organize complex sequences of reactions, participate in signal reception and energy transformations. What is the molecular makeup of membranes?
Why does bread expand? Bread is the leavened and cooked mixture of water, flour, yeast and a little s alt. If we mix flour and water we will obtain a sticky paste, but if we continue kneading we will obtain an elastic and malleable dough. How is it possible that almost the same mixture that is used to paste paper can also be turned into an exquisite bread?
In this second part, we will work with the physical concentration units. Percent mass by mass (% m/m) 1) 80 grams of a solution contains 20 grams of CuSO4. Calculate its concentration in % m/m. % m/m is defined as the mass of solute present in 100 grams of solution.
Chemistry is a natural and experimental science, since it is a science that deals with theory, through practice, and experimentation through a laboratory. Experimental chemistry is closely related to work in a laboratory, where we perform experiments, discovering laws that make chemical science more understandable, by unifying theory with practice.
At the beginning of the 19th century, enough elements and compounds were known that it was necessary to classify them in order to facilitate their understanding and study. From the beginning it was known of the existence of families of elements that shared properties and similarities with each other, intuiting that there must be a natural law that would tend to group and relate the elements logically.
Chemistry is the scientific discipline, which is responsible for studying matter and its transformations. Study the atoms, the combinations between them, their compounds and the reactions that can be formed between them. This vast science can be divided into:
The German physicist Arnold Sommerfeld , created in 1916, the atomic model that bears his name, to give some improvements to Bohr's atomic model, using the relativity ofAlbert Einstein , a theory that he had known when he entered as a professor at the University of Munich, when even the theory of relativity was not accepted.
The dipole-dipole interaction is that observed between a positive dipole of one polar molecule and the negative dipole of another. In polar covalent bonds, the atom with the higher electronegativity attracts electrons to itself, forming a negative dipole around it.
Commonly a substance is said to be hydrophobic when it is not miscible with water. From a chemical point of view, the molecules of the hydrophobic substance are not able to interact with water molecules, neither by hydrogen bonds nor by ion-dipole interactions.
The hydrogen bond is not actually a bond itself, but rather the attraction between an electronegative atom and a hydrogen atom that are part of different polar covalent bonds. The atom with the highest electronegativity will attract the electrons of the bond to itself, forming a negative dipole, while the hydrogen atom, by partially giving up its electrons, generates a positively charged dipole in its surroundings.
When we talk about corrosive substances , we are referring to substances that can cause the destruction of a surface or anything else that comes into contact with it, as well as create damage irreversible type. Of course, for people, these types of substances are also dangerous, as they can seriously damage the skin, mucous membranes, eyes, or tissues in a deeper way, depending on whether the substance in question has been ingested, inhaled or has simply entered direct contact
The octet rule states that the atoms of the elements bond with each other in an attempt to complete their valence shell (the last layer of the electrosphere). The name “octet rule” arose due to the established number of electrons for the stability of an element, that is, the atom is stable when it has 8 electrons in its valence shell.
The formic acid , also known under the name of methanoic acid, is an acid of organic chemistry, which is made up of only one carbon, for which, is one of the simplest organic acids that we can find. As for its chemical formula, it is quite simple, since it contains the acid functional group, attached to a hydrogen, that is, H-COOH or CH2O2.
In the field of medicine or chemistry, we speak of antacids to refer to substances or products based on an alkaline (basic) composition, which is used to fight against stomach acidity produced by the acids generated by the parietal glands. Thus, antacids act by alkalinizing the stomach environment, managing to increase the pH value.
The sulfuric acid, is perhaps one of the most famous chemical compounds popularly speaking, and this may be due to its high corrosive power that, mistakenly, gives it fame of the typical acid. It is the most produced chemical compound worldwide, since it has countless uses, as well as so much participation in different synthesis and production of so many products or other chemical compounds, in fact it is a meter used to know the capacity at an industrial level that features ea
The hydrocyanic acid , also known by other names such as hydrogen cyanide or prussic acid among many others, is a chemical compound with the molecular formula HCN (H-C≡N). By dissolving the hydrogen cyanide compound in H2O, hydrocyanic acid is produced.
Ion-dipole interaction is an intermolecular force that occurs when ions of a substance interact with the dipoles of a covalently polar molecule. In a polar bond, the atom with the higher electronegativity draws electrons toward itself, creating a negative dipole around itself, while a positive dipole forms in the area of the atom with the lower electronegativity.
It cannot be said that the acids and the bases are not foreign substances, we all make use of them on a daily basis, and it is not for exclusive use in laboratories as one might think. Every day we use substances whose use lies precisely in how acidic or basic they are.
We know that matter occurs in nature in three states: liquid, solid and gaseous. Gases have very marked differences in relation to other states. Properties of Gases The gas does not have its own volume: It has a volume equal to that of the container where it is contained.
Often, common and everyday objects need devices that supply the necessary electrical current for their correct operation. Such devices are called cells or batteries. The simplest battery and also the cheapest is the so-called, dry battery. There are many other, more sophisticated types such as mercury batteries, alkaline batteries, silver oxide or lithium batteries, etc.
The Pauli exclusion principle, was developed by the Austrian physicist Ernst Pauli in 1925. This quantum principle says that two particles (specifically fermions) that have the quantum numbers with which they are identical, cannot exist. This means that two electrons (fermions) in an atom cannot have the same quantum numbers at the same time.
We know as drinking water that which has the conditions to be consumed by human beings without restrictions, due to the previous treatments to which it has been subjected, insofar as It refers to purification, so it does not present any he alth risk.
A Lewis symbol is a symbol in which the valence shell electrons of an atom or simple ion are represented by dots placed around the element symbol. Each dot represents an electron. For example: Notice the examples that we present to you in which Chlorine has seven valence electrons, while Chloride has eight.
In most of the molecules we use every day in chemistry, the electron pairs in the valence shell of the central atom are shared by other atoms. However, there are many other polyatomic molecules and ions in which the central atom has an occasional pair of electrons that are not shared.
Sometimes a single Lewis structure does not give us all the information we need about a molecule, or it does not give us the complete information, so we need to have more than one Lewis structure, such as the case of the ozone molecule, from which we can draw two Lewis structures.
Some historical data presented in previous articles show that in fact, performing experiments to prove the existence of electric charges and electric forces is quite simple. We will state here as a summary the conclusion reached by Franklin, which is:
It is possible to establish a relationship between the amounts of solute dissolved in a given amount of solvent at a given temperature. For example, imagine that 10 g of s alt were mixed in 100 ml of water at 20ºC. We will see that the s alt dissolves completely and we can even place more s alt that will continue to dissolve.
Every chemical relationship tends to reach a state of equilibrium. However, this balance is not static and yes, dynamic. This means that, in a state of equilibrium, there is no total arrangement of defined structures of products and reactants, but there is a continuous formation and conversion of these into another, so that the amount of products formed is always the same in terms of that the amount of reactants will also remain the same, after equilibrium is reached.
Combustion is an exothermic chemical reaction, that is, they release heat into the environment. This type of reaction is very common since most of the energy we consume is derived from the burning of materials: fuels. Example: cooking gas, gasoline, oils and others, all of them obtained from the distillation of petroleum, are therefore classified as hydrocarbons.
In electrochemical processes there are frequent examples of mechanisms that are involved, stages of transfers of more than one electron or one or more species that participate in the global set of reactions. However, the cases where the simultaneous transfer of more than one electron is demonstrated for the same species that participates in a certain mechanism are quite rare.
Numerous procedures in metallurgy are carried out through the use of electrical energy. Among all of them, we can make special mention of electrolytic-type procedures that are indicated for obtaining different reducing metals, such as potassium, aluminum or magnesium, among others.
Thermochemistry is the branch of chemistry that deals with the heat exchanges that accompany reactions. Chemical reactions can be of two types Exothermic and Endothermic. Exothermic: When the reaction happens with release of heat (from the center to the outside).
This energy that is stored in substances, subjected to a constant pressure, we give the name of enthalpy and to represent it we use the capital letter “H”. We have already seen in a reaction of heat (energy) of each substance is transformed, being released (exothermic reaction) or absorbed (endothermic reaction).
The concentration of the substances alters the equilibrium in the following way: when the concentration of one of the products is increased, the equilibrium is displaced in the direction of the formation of the reactants; when the concentration of one of the reactants is increased, the equilibrium shifts in the direction of the formation of the products.
There are different types of adhesive substances that we will classify into four groups: 1- Adhesives that are sensitive to the solvent used or are activated by said solvent. 2- Hot melt adhesive substances 3- Substances that are adhesive thanks to chemical reactions 4- Latex adhesives.