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MIXTURES, SOLUTIONS AND PURE SUBSTANCES
Matter and its appearance
According to its appearance, there are two kinds of material systems:
Homogeneous systems: they have the same properties and compositions in all different parts of them.
Heterogeneous systems: different parts with different properties can be found in them.
Homogeneous Systems
Heterogeneous Systems
Heterogeneous Mixtures Systems with several different
substances that can be distinguished:
Oil and water. Granite is a rock that has three
different substances: quartz, mica and felspar.
Blood: using a microscope we can see a liquid (plasma) and different kinds of cells.
Smoke: has solid particles in a gas (air).
Heterogeneous Mixtures
How to separate their components:
– If the components are a solid and a liquid, we can separate them by filtering.• E. g.: water and
sand
Heterogeneous Mixtures
How to separate their components:
– Decantation: This method uses the different densities of the components to separate them:• (E.g.: oil and water)
Homogeneous Systems
There are two kinds of homogeneous systems:
Pure substances:
• They have only one component• They have constant
composition and properties. Solutions:
• They have several components.• Their composition can be
changed
Solutions A solution has, at least, two components:
Solute: It is the component that is present in a lower
quantity in the solution. Solvent:
It is the component that is present in excess. Its state never changes when the solution is being
formed
A simple sample: salty water: There is much more water than salt Water is a liquid and the solution too.
SOLUTE = SALT and SOLVENT = WATER
SolutionsThey are not always liquids !!!
Solutions
How to separate its components:
– Evaporation and crystallization: a liquid evaporates at room temperature, but a solid doesn't.
Solutions How to separate its components:
– Distillation: this method is useful to separate:• Liquids whose boiling points are different
• Liquids and solids
Pure SubstancesPure Substances
Pure substances: They have a constant composition. They can't be separated in simpler
substances using physical methods. There are two different kinds of pure
substances: Chemical compounds: pure substances
that cannot be separated using chemical methods.
Elements: pure substances that can't be separated into others
Four kinds of matterFour kinds of matter