Lesson 3 Introduction
Completion requirements
In a mixture, the substances blend together, but the atoms and molecules are not rearranged. In many situations, materials are mixed together that need to be separated.
Sometimes, this can be an easy process, but at other times, it can be much more difficult and complex.
A physical change is one in which the material's form changes, but the material itself does not change. Water which evaporates into water vapour is still made of the same matter, H2O.
A reversible change is one in which you can turn the substance back into its original form easily.
Some reversible changes can be made using heat, or by stretching (increasing the object's length), or compressing (applying force to decrease the object's length) the matter. Two examples are an elastic which can be stretched and mattress springs which can be compressed when you sit on them. These both return to their original shape. These are physical reversible changes.
Sometimes, this can be an easy process, but at other times, it can be much more difficult and complex.
A physical change is one in which the material's form changes, but the material itself does not change. Water which evaporates into water vapour is still made of the same matter, H2O.
A reversible change is one in which you can turn the substance back into its original form easily.
Some reversible changes can be made using heat, or by stretching (increasing the object's length), or compressing (applying force to decrease the object's length) the matter. Two examples are an elastic which can be stretched and mattress springs which can be compressed when you sit on them. These both return to their original shape. These are physical reversible changes.
Several techniques allow us to separate materials, but knowing the physical properties of the materials is essential to choose which technique will work.
Physical properties describe how a substance looks or behaves. Examples of physical properties include the following:
- colour, size, or shape of the particles
- boiling point and/or freezing point
- buoyancy (Does it float or sink in water?)
- magnetism (Is it magnetic?)
- solubility (Does it dissolve in water?)
The type of separation method best suited for a mixture depends on the physical properties of the various parts of the mixture.
Video
Watch this Separating Mixtures video to see some examples of methods of separation that you will be trying in this section.