Classification of chemicals

Classification of matter

• understanding matter begin with how we name it
• we can divide matter into 2 types: homogeneous substances and heterogeneous substances
• homogeneous: consist of only one visible component (destilled water, oxygen, graphite)
• heterogeneous: contain more than one visible component (chocolate chip cookie, granite)

Pure substances

•  there are 2 types of pure substances
•  elements: substances that cannot be broken down into simpler substances  by chemical reactions (oxygen, iron, magnesium)
•  compounds: substances that are made up of 2 or more element and can be changed into elements (or other compounds) by chemical reactions (water, sugar)

Solution

•  a solution is a homogeneous mixture of 2 or more substances
•  solutions usually involve liquids but don´t have to (fog, steel)
•  the component present in greater amount is the solvent
•  water is the most common solvent
•  the component present in smaller amount is the solute

Mixtures 

•  many mixtures are easy to identify (chocolate chip cookie), but others are easily confused as pure substances
•  in heterogeneous mixtures the different parts are clearly visible (granite, sand, fog)
•  in homogeneous mixtures the different parts are not visible (salt water, air, brass)

Separating mixtures

•  there are many methodes to separate mixtures, depending on the type of mixture

1. by hand 
2. filtration     --> physical       (heterogeneous
3. destillation  -->   changes              mixtures only)
4. crystallization
5. chromatography

 -Eva