1. MIXTURES, SOLUTIONS AND
PURE SUBSTANCES

2. Matter and its appearance

According to its appearance, there are two
kinds of material systems:

Homogeneus systems: they have the
same properties and compositions in all
different parts of them.

Heterogeneus systems: different parts
with different properties can be found in
them.

3. Homogeneus Systems

4. Heterogeneus Systems

5. Heterogeneus 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).

6. Heterogeneous Mixtures

How to separe their
components:
– If the components
are a solid and a
liquid, we can separe
them by filtering.
• E. g.: water and
sand

7. Heterogeneous Mixtures

How to separe their components:
– Decantation: This method uses the
different densities of the components to
separe them:
• (E.g.: oil and water)

8. Homogeneous Systems

There are two kinds of homogeneous
systems:

Pure substances:
• They have an only component
• They have constant
composition and properties.

Solutions:
• They have several components.
• Their composition can be
changed

9. 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

10. Solutions
They are not always liquids

11. Solutions

There three kinds of solutions:

Solvent + a small amount of solute =
diluid solution.

Solvent + a large amount of solute =
concentrate solution.

The quantity of solute that can be
dissolved has a limit (solubility). In this
case we have a satured solution.

If we try to dissolve more solute in a satured
solution, the extra quantity of solute will fall
onto the botton of the container.
(precipitation)

12. Solutions
Concentration of a solution:
– Expresses, in a numeric way, the quantity
of soluto un a specific quantity of
solution.
amountofsoluto
concentration=
amountofsolution
There are many ways of express it, depending of the
unit we use. We are going to study three of them.

13. Solutions
Concentration: grams per liter of solution.
massofsoluto ( g )
concentration ( g / L )=
Volumenofsolution
Sample: we put 20 grams of sugar in a 500-mililiters flask
and fill it in with water.
In the flask, there are:
20 g of soluto (sugar)
Soluto and solvent with a total volume of 500 mL = 0,5 L
concentration (g/L) = 20 g / 0,5 L = 40 g/L

14. Solutions
Concentration: percentage in mass
massofsoluto
concentration ( mass )= · 100
massofsolution
Sample: we add 25 grams of salt into a flask that contains
100 grams of water.
In the flask, there are:
25 g of soluto (salt)
100 g + 25 g = 125 g of solution (salt + water)
% mass = (25 g / 125 g) · 100 = 20 % in mass

15. Solutions
Concentration: percentage in volume
volumeofsoluto
concentration ( volume )= · 100
volumeofsolution
Sample: we mixure 20 mililiters of alcohol and 130 mililiters
of water:
We have:
20 mL of alcohol (alcohol)
130 mL + 20 mL = 150 mL of solution (alcohol + water)
% mass = (20 mL / 150 mL) · 100 = 13.3 % in volume

16. Solutions

How to separate its components:
– Evaporation and crystallization: a liquid
evaporates at room temperature, but a
solid doesn't.

17. Solutions

How to separate its components:
– Distillation: this method is useful to separate:
• Liquids whose boiling points are different
enough
• Liquids and solids

18. Pure 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 can be separated in others using
chemical methods.

Elements: pure substances that can't be
separated in others

19. Compound

Pure substance composed of two or more different elements
joined by chemical bonds.

Made of elements in a specific ratio that is always
the same

Has a chemical formula

Can only be separated by chemical means, not
physically

There are millions of different compounds in nature

20. Compound

¿Compound or Mixture?

21. Element

It is the simplest kind of matter.

Has a chemical symbol.

Can't be separated in
others substances

There are only about one hundred
elements in natures. All of them are
in the Periodic Table

22. Four kinds of matter

23. Four kinds of matter

24. Four kinds of matter