2.3 Pure substances (ESAZ)

Any product that is not a mixture, is called a pure substance. Pure substances incorporate elements and also compounds. The is lot more difficult to failure pure substances right into their parts, and facility chemical approaches are necessary to carry out this.

You are watching: Is nitrogen a pure substance or mixture

We can use melting and also boiling points and also chromatography to test for pure substances. Pure substances have actually a sharply defined (one temperature) melt or cook point. Impure substances have a temperature variety over which castle melt or boil. Chromatography is the procedure of separating substances into their individual components. If a substance is pure then chromatography will certainly only develop one substance at the finish of the process. If a substance is impure then number of substances will be viewed at the finish of the process.

Recommended handy activity: Smartie chromatography

You will certainly need:

filter record (or blotting paper)

some smarties in different colours


an eye dropper.

Place a smartie in the center of a item of filter paper. Closely drop a few drops the water onto the smartie, till the smartie is quite wet and also there is a ring of water top top the filter paper. After part time you need to see a coloured ring ~ above the file around the smartie. This is since the food colouring the is used to do the smartie colourful dissolves in the water and is carried through the document away indigenous the smartie.

Smartie chromatography


Elements (ESAAA)

An element is a chemical substance that can"t be split or changed into other chemical substances by any ordinary chemistry means. The smallest unit the an element is the atom.


An facet is a substance the cannot be damaged down into other substances with chemical means.

There are ( ext112) officially named facets and around ( ext118) recognized elements. Many of these are natural, but some space man-made. The elements we recognize are stood for in the periodic table, whereby each aspect is abbreviation to a chemical symbol. Table 2.2 provides the an initial ( ext20) elements and also some the the common transition metals.

Recently it to be agreed that two an ext elements would be included to the perform of officially called elements. This are aspects number ( ext114) and also ( ext116). The proposed surname for aspect ( ext114) is flerovium and also for facet ( ext116) that is moscovium. This brings the total number 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 facets combine in a addressed ratio. Water (( extH_2 extO)), for example, is a compound that is comprised of two hydrogen atoms for every one oxygen atom. Salt chloride (( extNaCl)) is a compound made up of one salt atom because that every chlorine atom. Crucial characteristic the a compound is that it has actually a chemical formula, which defines the proportion in i beg your pardon the atom of each element in the compound occur.


A substance made up of two or an ext different elements that space joined with each other in a fixed ratio.

Figure 2.4 might help you to know the difference in between the terms element, mixture and also compound. Steel (( extFe)) and also sulfur (( extS)) are two elements. As soon as they are added together, they form a mixture the iron and also sulfur. The iron and sulfur room not join together. However, if the mixture is heated, a brand-new compound is formed, which is called iron sulfide (( extFeS)).


Figure 2.4: A mixture that iron and also sulfur


Figure 2.5: A version of the iron sulfide crystal

Figure 2.4 showed a submicroscopic representation of a mixture. In a submicroscopic depiction we usage circles come represent different elements. To show a compound, we draw several circles joined together. Mixtures room simply presented as two or more individual elements in the very same box. The circles space not joined for a mixture.

We can also use signs to stand for elements, mixtures and also compounds. The icons for the facets are all uncovered on the regular table. Link are displayed as two or an ext element names written right alongside each other. Subscripts might be provided to display that there is an ext than one atom the a specific element. (e.g.( extH_2 extO) or ( extNH_3)). Mixtures room written as: a mixture of element (or compound) A and also element (or compound) B. (e.g. A mixture the ( extFe) and ( extS)).

Worked example 2: Mixtures and also pure substances

For each of the complying with substances state whether it is a pure substance or a mixture. If it is a mixture, is it homogeneous or heterogeneous? If that is a pure substance is the an facet or a compound?

Blood (which is made up from plasma and also cells)


Silicon dioxide (( extSiO_2))

Sand and stones

Apply the definitions

An aspect is discovered on the periodic table, so us look in ~ the regular table and also find that just argon shows up there. Next we decision which room compounds and which are mixtures. Compounds consist of two or an ext elements join in a resolved ratio. Sand and also stones space not elements, neither is blood. However silicon is, as is oxygen. Finally we decide whether the mixtures room homogeneous or heterogeneous. Since we cannot view the separate components of blood it is homogeneous. Sand and stones space heterogeneous.

Write the answer

Blood is a homogeneous mixture.

Argon is a pure substance. Argon is an element.

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

Sand and stones type a heterogeneous mixture.

Using models to represent substances

The following substances space given:

Air (consists that 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 material given.

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

Draw submicroscopic depictions for each of the over examples.

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Elements, mixtures and also compounds

In the following table, tick whether each of the substances provided is a mixture or a pure substance. If the is a mixture, likewise say whether it is a homogeneous or heterogeneous mixture.