Chemistry for foreign students in Belarus. Lesson #2 Pure substances and mixtures Autor Yauheni Slizh email: kiolk@tut.by skype: tyteihi

1. Pure substances and mixtures
Chemistry/topic 2

2. As you know, every substance has a
characteristic set (complex) of
properties on which it can always be
distinguished
from
any
other
substance. However, these properties
are well-defined only for a single
individual substance that is not mixed
with other substances. So necessary
to
distinguish
between
pure
substances from mixtures.

4. • Pure are substances that do not contain
impurities of other substances.

5. Mixture - a collection of individual compounds
that make up the physical body.

6. Homogeneous refers to substances and mixtures
which are in a single phase.
from Ancient Greek
ὁμογενής (homogenēs) from ὁμός (homos,
“same”) followed by γένος (genos, “kind”)

7. Heterogeneous in the sciences is a substance
composed of dissimilar or diverse parts.
from Ancient Greek
ἑτερογενής (heterogenēs), from ἕτερος (heteros,
“other, another, different”) respectively,
followed by γένος (genos, “kind”).

8. Types of mixtures

9. Types of mixtures

10. Suspension is a heterogeneous mixture
containing solid particles that are sufficiently large
for sedimentation. Usually they must be larger than
1 micrometer.
A colloid is a substance microscopically dispersed
throughout another substance.
The dispersed-phase particles have a diameter of
between approximately 1 and 1000
nanometers.
Solution is a homogeneous mixture composed of
only one phase. In such a mixture, a solute is a
substance dissolved in another substance, known
as a solvent.

12. Sedimentation (Defending)
• This is one of the easiest methods of
separation. It is based on the fact the fact
that the components of the mixture
have different density. This method
can be divided heterogeneous mixture of
two liquids, such as oil and water, liquids
and solids (sand and water).

13. Filtration
• When filtering requires a special filter.
Filter can serve as special paper, special
glass, gauze or cotton. The use of filters
depends on how big the particles of
one component of the mixture. We
will try to divide a heterogeneous mixture
of solid and liquid substances, water and
chalk.

14. Sedimentation, Decantation and
Filtration

15. Evaporation
• The method is based on the fact that
different
materials
have
different
degrees of volatility. For example, water and
alcohol are volatile substances, salt and alkali non-volatile. Take a mixture of salt and water.
This mixture is homogeneous or not? Will heat
the mixture. What's going on? The water
evaporates and condenses on the glass, the salt
remains in a solid. Tell me, which one of the
components of the mixture is volatile?
• This method is widely used in the extraction of
salt from natural brine.

16. Time Lapse Formation of Salt
Crystals (Evaporation)

17. Distillation
• The method is based on the fact that
different components of the mixture
have different boiling points. Most
often, this method is used to separate a
homogeneous mixture of liquid substances.

18. Separation of Mixtures using Fractional Distillation
- OLabs- Amrita University(Distillation)

19. Recap quiz:
1) Give examples of almost pure substances
with which you meet in everyday life.
2) Give five examples of homogeneous and
heterogeneous mixtures, you meet every
day
3) How to distinguish a pure substance
from a mixture of substances?

20. Recap quiz:
4) Homogeneous or heterogeneous mixture is
formed by mixing:
• a) alcohol and water;
• b) flour and water
• a) starch and sugar;
• d) of oil and water
• e) weak tea and sugar;
5) Why is not found in nature is pure water?
6) What are the methods most often used for
the separation of homogeneous mixtures?
7) What are the methods most often used for
the separation of heterogeneous mixtures?

21. Home task:
• Learn definitions which you wrote
on the lesson
• Pleas write 5 examples of the
types of mixtures which you are
using in your life?

22. • https://www.facebook.com/groups/267369
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• kiolk@tut.by
• Skype: tyteishi