Changes in materials

How do things change?
There's two type of changes. Reversible and non-reversible.

What is a reversible change?

Reversible change is changes in materials that can be changed back into their original form.
Examples of reversible change is an ice cube. When an ice cube melts, it becomes a water. Then, a water that is freez is form into an ice cube again.
 http://www.youtube.com/watch?v=MsNfDKkU9ZM

What is a non-reversible change?

Non-reversible change is changes in materials which cannot turn back to their original form.
Examples of non-reversible change is burning a paper. When a paper is burned, it form an ash and the ash cannot change back to a paper or their origanal form.
http://www.youtube.com/watch?v=c-pK6ltdEps

Factors that cause rotting of wood

The rotting of wood is a non-reversible change. It takes place when there is a wood rot fungi and moisture.
When wood is exposed to moisture in the air, it becomes moist. Moist wood is home tobwood rot fungi.
Wood rot fungi attack wood cells which cause the wood become porous and crubbly. Wood rot fungi and moisture cause the wood of the fence to rot and turn black.

Factors that cause rusting

Rust is a layer of reddish-brown substance that is formed on metals such as iron and steel. Rusting is the formation of rust on metals.
The rusting of materials is a non-reversible change. It takes place when there is oxygen and moisture.
When a metal is exposed to the air, it combines with oxygen and moisture. As a result, rust slowly form.
Oxygen and moisture in the air cause rust to form on the metals railings.

Experiment on the science lab.
-Heating a white sugar. After a few minutes, it melts and the colour becomes brown and hard. This is a physical/reversible change.

-Heating a butter does not change it's colour. It just melts. This is also a reversible change.

-Heating a candlewax doesn't form a new material. When it melts, the colour becomes transparent and after a few minutes, it changes to the orginal materials again. This is a reversible change.
-Mixing a flour with water. When this materials mixed, they become a liquid. It does not form a new materials or can be called as reversible change.
-Mixing baking soda with vinegar. When they are mixed, it becomes a liquid and there is puffing bubble above the liquid. This called as a chemical or non-reversible change.