2.3 Pure substances (ESAZ)

Any material that is not a mixture, is referred to as a pure substance. Pure substances include elements and also compounds. The is much more complicated to failure pure substances into their parts, and complicated chemical approaches are essential to do this.

You are watching: Hydrogen and chlorine are pure substances or

We can use melting and also boiling points and also chromatography come test because that pure substances. Pure substances have actually a sharply identified (one temperature) melting or cook point. Impure substances have a temperature variety over which they melt or boil. Chromatography is the process of separating substances right into their separation, personal, instance components. If a problem is pure climate chromatography will only develop one problem at the end of the process. If a substance is impure then number of substances will certainly be watched at the finish of the process.

Recommended practical activity: Smartie chromatography

You will certainly need:

filter record (or blotting paper)

some smarties in various colours


an eye dropper.

Place a smartie in the centre of a piece of filter paper. Closely drop a few drops of water onto the smartie, until the smartie is quite wet and there is a ring that water top top the filter paper. After some time you should see a coloured ring ~ above the document around the smartie. This is because the food colouring the is supplied to make the smartie colourful disappear in the water and is lugged through the record away native the smartie.

Smartie chromatography


Elements (ESAAA)

An element is a chemistry substance that can"t be divided or adjusted into various other chemical building materials by any ordinary chemical means. The the smallest unit the an aspect is the atom.


An facet is a substance the cannot be broken down into other substances v chemical means.

There are ( ext112) officially named aspects and around ( ext118) known elements. Most of these are natural, but some room man-made. The facets we know are stood for in the periodic table, whereby each aspect is abbreviation to a chemical symbol. Table 2.2 offers the very first ( ext20) elements and also some of the common change metals.

Recently it to be agreed that two much more elements would be included to the list of officially named elements. This are elements number ( ext114) and also ( ext116). The proposed surname for aspect ( ext114) is flerovium and also for facet ( ext116) it is moscovium. This bring the total variety of officially named aspects to ( ext114).

Element name

Element symbol

Element name

Element symbol


( extH)


( extP)


( extHe)


( extS)


( extLi)


( extCl)


( extBe)


( extAr)


( extB)


( extK)


( extC)


( extCa)


( extN)


( extFe)


( extO)


( extNi)


( extF)


( extCu)


( extNe)


( extZn)


( extNa)


( extAg)


( extMg)


( extPt)


( extAl)


( extAu)


( extSi)


( extHg)

Compounds (ESAAB)

A compound is a chemistry substance that forms when 2 or more different aspects combine in a fixed ratio. Water (( extH_2 extO)), for example, is a compound that is comprised of two hydrogen atoms for every one oxygen atom. Sodium chloride (( extNaCl)) is a compound consisted of of one sodium atom for every chlorine atom. Vital characteristic the a compound is that it has actually a chemical formula, which defines the proportion in which the atom of each facet in the compound occur.


A substance consisted of of two or an ext different aspects that room joined with each other in a fixed ratio.

Figure 2.4 might aid you to know the difference in between the state element, mixture and compound. Iron (( extFe)) and also sulfur (( extS)) room two elements. As soon as they are added together, they form a mixture the iron and sulfur. The iron and also sulfur room not joined together. However, if the mixture is heated, a new compound is formed, which is dubbed iron sulfide (( extFeS)).


Figure 2.4: A mixture the iron and also sulfur


Figure 2.5: A design of the iron sulfide crystal

Figure 2.4 verified a submicroscopic depiction of a mixture. In a submicroscopic representation we usage circles to represent different elements. To display a compound, we attract several circles join together. Mixtures are simply displayed as 2 or much more individual facets in the same box. The circles space not joined for a mixture.

We can additionally use signs to represent elements, mixtures and compounds. The symbols for the facets are all uncovered on the regular table. Link are presented as 2 or much more element names composed right next to each other. Subscripts may be used to display that over there is much more than one atom of a specific element. (e.g.( extH_2 extO) or ( extNH_3)). Mixtures space written as: a mixture of element (or compound) A and element (or compound) B. (e.g. A mixture of ( extFe) and also ( extS)).

Worked instance 2: Mixtures and also pure substances

For every of the complying with substances state even if it is it is a pure substance or a mixture. If it is a mixture, is it homogeneous or heterogeneous? If it is a pure substance is the an element or a compound?

Blood (which is made up from plasma and cells)


Silicon dioxide (( extSiO_2))

Sand and stones

Apply the definitions

An element is discovered on the regular table, so us look at the routine table and find that only argon appears there. Following we decision which are compounds and also which room mixtures. Compounds consist of 2 or much more elements join in a solved ratio. Sand and also stones space not elements, neither is blood. Yet silicon is, together is oxygen. Ultimately we decide whether the mixtures space homogeneous or heterogeneous. Because we cannot view the separate components of blood it is homogeneous. Sand and also stones space heterogeneous.

Write the answer

Blood is a homogeneous mixture.

Argon is a pure substance. Argon is one element.

Silicon dioxide is a pure substance. It is a compound.

Sand and also stones form a heterogeneous mixture.

Using models to represent substances

The following substances are given:

Air (consists the oxygen, nitrogen, hydrogen, water vapour)

Hydrogen gas (( extH_2))

Neon gas


Ammonia gas (( extNH_3))

Use coloured balls to build models for each of the building materials given.

Classify the substances follow to elements, compounds, homogeneous mixtures, heterogeneous mixture, pure substance, impure substance.

Draw submicroscopic depictions for each of the above examples.

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Elements, mixtures and compounds

In the following table, tick whether every of the substances provided is a mixture or a pure substance. If it is a mixture, additionally say even if it is it is a homogeneous or heterogeneous mixture.