Elements, compounds & mixtures

A introductory journey into chemistry.

1. Elements, Compounds &
Mixtures
Introductory Chemistry

2. States of Matter
Properties of Solids, Liquids & Gases
Changes of State cycle
Particle Theory

3. Eternal Questions
People have long asked:
“What is the world made of?”
“Le Penseur” (The Thinker) -AugusteRodin

4. Particle Theory
Scientists have come to realize that the matter of the world is
made from a few fundamental building blocks of nature.
The word"fundamental"is key here. By fundamental building
blocks we mean objects that are simple and structure-less--
not made of anything smaller.
The particle theory says;
-that all matter consists of many, very small particles
-The particles are constantly moving (they have kinetic
energy) or in a continual state of motion.
-The higher the temperature, the faster the particles move
-The differences between solids, liquidsand gasescan be
explained by this theory.

5. Properties of Solids
In a solid, particles of matterare packed closely together and
are not free to move about within the substance.
Motion for the particles in a solid is confined to very small
vibrations of the atoms around their fixed positions; therefore,
solids have a fixed shape that is difficult to change. Solids also
have a definite volume; that is, they keep their size no matter
how you try to change them.

6. Properties of Liquids
The particles in a liquid are attracted to each other;
however, liquid particles have more space between them, so
they are not fixed in position.
The attraction between the particles in a liquid keeps the
volume of the liquid constant.
Liquids will flow and fill the lowest portion of a container,
taking on the shape of the container but not changing in
volume.
The limited amount of space
between particles means that
liquids have only very limited
compressibility.

7. Properties of Gases
Gas particles have a great deal of space between them and if
unconfined, the particles of a gas will spread out indefinitely; if
confined, the gas will expand to fill its container.
When a gas is put under pressure by reducing the volume of the
container, the space between particles is reduced, and the
pressure exerted by their collisions increases.
If the volume of the container is held constant, but the
temperature of the gas increases, then the pressure will also
increase.
Gas has no definite volume and no definite shape.

8. Changing State Diagram

9. Getting Smaller
Atoms
The Periodic Table
-Atomic Number (Z)
-Groups & Periods
-Noble Gases
-Metals, Non-Metals, Metalloids

10. Atoms
By convention there is colour,
By convention sweetness,
By convention bitterness,
But in reality there are atoms and space.
-Democritus (c. 400 BCE)

11. Everything in the world is made up of
small parts.

12. Atoms?
There are about 100 types of atoms.
Each different type is called an element.
Each element has a symboland a name.
For example… the 8
th
smallest element is called ‘Oxygen’.
Its symbol is O

13. Elements
Elements are only made up of one type of atom.
Everything else is made up of combinations of different
atoms.

14. What’s in an atom?
An atom is made up of threeparts.
All of the mass is concentrated in the ‘nucleus’ in the
middle. The nucleus makes up almost all of the mass of
the atom.
The nucleus is made up of positively charged protonsand
neutronsof no charge.
The number of protons tell us
which element it is.
This has 7 protons so it is
Nitrogen.

15. Electrons
Outside the nucleus there are rings of electrons.
There are the same number of electrons as protons but
with the opposite charge (negative).
Electrons don’t really weigh anything.

16. So..
In reality, the electrons are very far from the nucleus.
If the nucleus was the size of a sugar cube in the centre of
the MCG, the electrons would be as distant as the
outermost seats.
If the nucleus was the size of a soccer ball, the electrons
would be 20 kilometres away.

17. Rutherford
A New Zealander found this out by firing radiation at a
thin piece of gold.
He discovered that most of an atom is EMPTY SPACE.

18. YOU are made of atoms.
YOU ARE MOSTLY EMPTY SPACE.
Since, all of the atoms from Earth are from extinct stars…
YOU ARE MOSTLY EMPTY SPACE AND THE BIT THAT IS
HERE IS FROM AN EXTINCT STAR

19. IN FACT, IF YOU SQUISHED OUT
ALL OF THE EMPTY SPACE FROM
ALL OF THE PEOPLE ON EARTH,
THE AMOUNT THAT WEIGHS
ANYTHING (THE NUCLEI)
WOULD BE THE SIZE OF A GRAIN
OF RICE.
FREAKY.

20. Atoms
An atomis the smallest particle of a chemical
element that can exist.
An atom consists of a nucleusat the centre,
surrounded by a cloud of one or more electrons.
The nucleusis made up of
protons and neutrons
-Protonsare positively
charged particles
-Neutronshave no
charge (are neutral)

21. Inside the Atom
Is mostly empty space!

22. The Periodic Table
Dmitri Mendeleev (1834 –1907)

23. Atomic Number -History
The first attempts at constructing a Periodic Table listed
atoms in order of their atomic weight –each atom was
thus given an atomic number.
In 1911, Ernest Rutherford, NielsBohr and Antonius van
der Broeksuggested that this could be improved by
ordering them based upon the charge of their nucleus.
In 1920, Rutherford discovered
protons–which were shown to match
exactly with the atomic number.
The symbol for atomic number, Z,
comes from the German word
Atomzahl, meaning ‘atomic number’.

24. Atomic Number
In modern chemistry, the atomic number of an
atom is designated by the letter Z.
The atomic number of an element matches the
number of protons within the nucleus.
For example:

25. Groups & Periods
The periodic table has rows –called periods -and columns
–called groups -and each of these specific characteristics.
Elements in the same groupshare similar chemical
characteristics.
Elements in the same periodhave the same number of
orbitals(layers of electrons circling the nucleus).

26. Noble Gases
The happy elements in Group 18
Noble gases have full outer shells of electrons so they are
not chemically reactive, they are inert.
Helium has 2 electrons in its outer shell, Neon has 8

27. Metals, Non-Metals,
Metalloids..
Differences across the table.

28. Metals
Metals have several features in common:
-They are solid at room temperature, except for
mercury which is a liquid.
-They can be polished to produce a high shine orlustre.
-They are goodconductorsof electricity and heat.
-They can all be beaten or bent into a variety of shapes.
We say they aremalleable.
-They can be made into a wire. We say they areductile.
-They usually melt at high temperatures. Mercury,
which melts at −40 °C, is one exception.

29. Non-metals
Only 22 of the elements are non-metals. At room temperature,
eleven of them are gases, ten are solid and one is liquid. The
solid non-metals have most of the following features in
common:
-They cannot be polished to give a shine like metals; they are
usually dull or glassy.
-They arebrittle, which means they shatter when they are
hit.
-They cannot be bent into shape.
-They are usually poor conductors of electricity and heat.
-They usually melt at relatively low temperatures.
-Many of the non-metals are gases at room temperature.

30. Metalloids
Some of the elements in the non-metal group look like metals.
One example is silicon.
While it can be polished like a metal, silicon
is a poor conductor of heat and electricity
and cannot be bent or made into wire.
Elements that have some features of both
metals and non-metals are called
metalloids.
There are eight metalloids altogether:
boron, silicon, germanium, arsenic,
antimony, tellurium, polonium and
astatine.

31. Uses for Metals –Based on their
Properties
Copper is ductile& conducts electricityvery well, hence
its use in electrical wiring.
Iron is strong&malleable, which makes it
perfect for large construction. When
combined with other metal & non-metal
elements (called an alloy) –it becomes an
ideal construction material.
Steel is an alloyof carbon & iron.
The lustreof metals has also seen their
use in many forms of jewellery.

32. Uses for Non-Metals –based on their
properties
Non-metals also have extensive uses. Solid
carbon, when exposed to extreme pressure,
creates diamonds.
Neon gas is inertso it
doesn’t react –it just
glows red/orange in a
vacuum discharge tube,
creating the ubiquitous
‘Neon Signs’.
Silicon is used in integrated circuits
because of its low conductivityto
electricity & heat (silicon is called a
semiconductor). This property enabled
modern computers to exist.

33. Compounds & Mixtures

34. Sorting
All substances can be organised into one of three
categories;
-Elementscontain only one type of atom. Few things
around us exist purely as elements.
-Compounds (short for Compound Molecules) are made
up of two or more elements bondedtightly together.
They are usually very different from the elements that
make them up.
-Mixtures are made up of two or more elements, two
or more compounds, or a combination of both.

35. Molecules
Moleculeis the general term used to describe any atoms
that are connected bychemical bonds
Every combination of atoms is a molecule.
Simple:
Complex: Ridiculous:

36. Molecules can be atoms of just one
Element…

37. Compounds
When molecules include different atoms (elements) they are called
compound molecules or just ‘compounds’.

38. Compounds
A compound moleculeis a molecule made of atoms from
differentelements.
All compounds are molecules, but not all molecules are
compounds.
Hydrogengas (H
2) is a molecule, but not a compound
because it is made of only one element.
Water (H
2O) can be
called a compound
moleculebecause it
is made of hydrogen
(H) and oxygen (O)
atoms

39. Mixtures
a mixture:
-consists of two or more different elements and/or
compounds physically intermingled,
-can be separated into its components by physical
means, and
-often retains many of the properties of its components.

40. Draw these!
Mixtures do not have official scientific names –for
example, air is just called ‘air’.
Compounds are named according to the different
elements they are made of..
For example; carbon dioxide, iron oxide, sodium chloride.

41. Molecular Formulae
Compounds and molecules also have a ‘formula’ -
an abbreviated way of writing what they are made of.
Water: H
20
Carbon Dioxide: CO
2
Carbon monoxide: CO
Salt (sodium chloride): NaCl
This is why we ask you to learn the symbols for the first 20
elements! So in future years you can identify compound
molecules…

42. Similarities & Differences
Mixture Compound
CompositionVariable composition –you
can vary the amount of
each substance in a
mixture.
Definite composition –you
cannot vary the amount of
each element in a
compound.
Joined or notThe different substances
are not chemically joined
together.
The different elements are
chemically joined together.
PropertiesEach substance in the
mixture keeps its own
properties.
The compound has
properties different from the
elements it contains.
SeparationEach substance is easily
separated from the
mixture.
It can only be separated into
its elements using chemical
reactions.
Examples Air, sea water, most rocks.Water, carbon dioxide,
magnesium oxide, sodium
chloride.

43. Refresh!

44. Title
Content