Chemical reactions

Chemical reactions change the properties of the original substance, and a new substance is formed.

Here are three types:

Combustion produces energy in the form of heat and light. Combustion (or burning) can happen when oxygen in the atmosphere reacts with a fuel, such as wood, gas, or oil.

Oxidation can occur with metals (rust) or in foods like apples.

Fermentation is a chemical reaction where fungi or bacteria change organic substances into other substances.

During the process of fermentation, fungi produce alcohol and bacteria produce lactic acid.  This way we can get foods like yoghurt, wine, bread, and cheese.

Decantation

Decantation is used to separate:

-- a solid from a liquid (sand and water)

--two liquids of different densities (oil and water)





Decantation to separate a solid from a liquid:





Decantation to separate two liquids of different densities:

Magnetic separation

Here is a machine that uses magnets to separate wood from nails.





and to separate iron from sand:





and for recycling:

Pure Substances and Mixtures

Matter is everything around us that takes up space and has mass.  We can classify matter into pure substances and mixtures.

Pure substances have only one type of particle. They can be made of elements or compounds.

Elements have only one type of atom. They are classified in the Periodic Table:

Do you know what these symbols mean?  Au,  Fe, H, O, Na, Cl, C

Compounds are made up of two or more elements combined in a particular way. For example: H20 or  NaCl. 

                     

     

To separate a compound, you must perform some type of chemical reaction.

A mixture is a combination of pure substances.   

In heterogeneous mixtures, we can see the different parts with the naked eye.

In homogeneous mixtures, you can't see the individual parts. It all looks the same:

Watch this short video: