MATTER - PURE SUBSTANCES AND MIXTURES. 

Matter exist in nature as pure substances and mixtures. Pure substances are not very common. The vast majority of substances are mixtures. 

Analyze the following classification to understand better the classification

 

 

Image result for libretext pure substances and mixtures

 

 

Pure substances and Mixtures

Substances can be pure or impure.

Pure substances

Pure substances are the ones that have a definite composition, this means that if we take a sample from different zones in the substance, the properties will be the same. 

They can be identified by their intensive properties. Example: Boiling and Melting point, density, etc. 

Elements are pure substances: Elements cannot be broken into simpler substances because they contain only one kind of atoms. Examples: H2, O2, Cl2, Na, Ne, Ar, etc.

These elements can be found in the periodic table.

solids liquids and gases as pure elements

Compounds are pure substances: Compounds that can be broken in simpler substances because they are formed by 2 or more atoms combined together. Examples: water, sulfuric acid, sodium chloride, ethanol, etc

compounds pure substances

Impure Substances

Mixtures are NOT pure substances

When two or more compounds or elements are mixed together, we have a mixture. 

Heterogeneous Mixtures

Their properties very throughout the substance

heterogeneous mixture

Homogeneous Mixtures - Solutions

Their properties are the same in any point of the substance. Homogeneous mixtures are also called solutions. Example: Sea water, brass, bronze, etc. These mixtures can be solid, liquid or gases

homogeneous mixtures

 

Exercises: 

Classify the following substances in pure substances (elements or compounds) and mixtures (homogeneous or heterogeneous).

 substance

 mixture
or
pure substance

element
or
compound
homogeneous
or
heterogeneous
 sodium      
 iron      
 water      
 salt water      
 soil      
 acetone      
 coffee      
 nitrogen      
 oxygen      
 Eggs      
 isopropyl alcohol       
 Blood      
 carbon dioxide      
 table salt      
 carbon dioxide      
 gasoline      
 air      
 milk      
 sulfuric acid      
 silver nitrate          
   
© Analia Sanchez