WHAT'S OXIDATION?

Oxidation is a chemical reaction in which an atom loses one or more electrons to oxygen atoms. Oxidation causes changes to the properties and appearance of substances.
Types of oxydation:
Rusting: When iron is exposed to oxygen in the air, its electrons are lost. Rusting can cause problems in vehicles. To prevent this, vehicles are painted.
 

Oxidation in fruit: When the fruit is exposed to the air, its electrons are lost. When this happens, a chemical change takes place, and the part of the fruit that has oxidised is no longer good to eat.


Fermentation: is a chemical reaction in which an organism such as yeast or bacteria, changes sugar and carbohydrates into alcohol or an acid.

WHAT ARE CHEMICAL CHANGES?

Chemical changes occur when one or more substances combine to form a new substance. A chemical change is non-reversible.

Image from sjesci 

The process in which two or more substances combine chemically is called a chemical reaction.
Some chemical reactions produce thermal energy; these are called exothermic reactions.


Other reactions absorb thermal energy; these are called endothermic reactions.


Combustion, or burning, is the name for a chemical reaction in which oxygen combines with a fuel, such as wood, coal or natural gas. It is an exothermic reaction.


We use combustion in various ways:

• Petrol and diesel are burnt to power vehicles and to heat homes.
• Coal is burnt in power stations to generate electricity.
• We burn natural gas to cook and heat our homes.

Combustion causes problems:

• Most fuels produce carbon dioxide during combustion. Carbon dioxide contributes to global warming.
• Burning coal, petrol or diesel produce particles that pollute the air.
• Burning coal and diesel can produce an acid called sulphur dioxide. If sulphur dioxide mixes with rainwater, it produces acid rain.