Pure substances and mixtures
Air pure substance or mixture
Everything in this world that occupies space is defined as matter. Matter can be divided into two main categories, pure substance or mixture. A pure substance is made up of the same types of molecules, elements and compounds are the basic examples of such matter, while mixture is made up of two different types of molecules, homogeneous mixtures and heterogeneous mixtures are the main types of mixtures . Pure Substance as its name has refers exists in the purest possible form, has no impurities within it and the same composition and properties throughout, and on the other hand, mixture is the combination of two or more different molecules, and each constituent tries to retain its identity in them.furthermore, mixtures are formed without any chemical reaction between the substances;
Pure substances are the type of matter that is formed with the same type of molecules. They have a sharp melting and boiling point, as they exist in the purest form. To determine whether the substance is pure or not, the chemical method is applied to verify purity. Pure substances possess similar properties and composition throughout. Since they are in their purest form, they cannot be divided into different components even by using chemical or physical processes. Pure water is one of the basic examples of a pure substance, although this water soon becomes a mixture when impurities or other substances are mixed into it.
Pure substances and mixtures examples
1. Pure Substances: Formed by a single type of substance, they have a fixed or defined composition in the different physical states of matter (liquid, solid and gaseous), they have characteristic properties, such as boiling temperature (specific and constant) or density. These can be the chemical elements and compounds.
a) Chemical elements: Simple substances composed of a single type of particles (atoms) and cannot be decomposed into other simpler substances. They are represented by symbols in the periodic table (Figure 1), for example Oxygen (O), Zinc (Zn), copper (Cu), carbon (C), sodium (Na), among others.
b) Chemical Compounds: Union of two or more different substances (atoms), in fixed and exact quantities. They can be decomposed into simpler substances through chemical methods. They are represented by chemical formulas that express the quantities and types of chemical elements that compose them (Figure 2).
Mixtures: A combination of two or more pure substances, which may be in varying quantities while retaining their individual properties. Their components can be separated or obtained by physical methods. They are classified into Homogeneous Mixtures and Heterogeneous Mixtures.
Water is a pure substance
In the first procedure, we saw that copper (Cu) is a pure substance because it has only one type of atoms which is noticeable because it is a uniform substance, that is, it was noticeable that there was nothing other than Cu atoms.
And we also learned that the mixture we got, sulfur (S) with iron (Fe), is a mixture because there are no chemical bonds between them and they can be separated as we did in one of the next procedures.
We met sodium (Na), a metallic element that reacts with air and water. At first, we concluded that Na was an element by discard, but then we investigated and were able to confirm our hypothesis.
And as a compound, we met copper sulfate (CuSO4 . 5H2O), a blue-colored Cu salt crystal with a rhombic shape. We thought it was salt because of its physical characteristics and we were right. It was a compound formed by molecules of sulfur oxide (SO) and Cu. Then we entered the separation area.
With this, we learned, among other things, that Fe is easily magnetized and that day magnetism is another method of separating mixtures. And finally, we were asked what we could separate: the element or the compound that had been given to us in one of the previous procedures.
Simple pure substances
Pure substances and mixtures.let’s review everything we have studied so far: Matter is what things are made of. Matter has two properties: mass and volume; the relationship between the two is density. Matter is found in three states: solid, liquid and gas. Matter can change state: melting, solidification, vaporization, condensation and sublimation.
Types of mixtures. Mixtures (consisting of several pure substances called components), can be divided into two groups. The classification depends on whether or not their components are distinguished. Thus, we find: Homogeneous mixtures. Heterogeneous mixtures.
Separation of components of mixtures.As mixtures are the union of several pure substances (homogeneous or heterogeneous), we can sometimes separate their components. In sea water, composed of water and salt, we are interested in separating the salt for use in cooking.
Separation of components of mixtures.Filtration: It is used to separate a solid from a liquid, for which the mixture is passed through a porous paper filter, retaining the solid. Example of filtration to separate sand and water.