Transcript Elements, Compounds and Mixtures

Elements, Compounds and
Mixtures
Chapter 3
Elements

A pure substance that cannot be separated
into simpler substance by physical or
chemical means
One Particle
An Element Has Only One
Type of Particle

Pure substance- a substance in which there
is only on type of particle (atom)
Every element Has a Unique
Set of Properties

Characteristic Properties- properties that do
not depend on quantity
Chemical Properties

Physical Properties



Boiling Pt
Melting Pt
Density

Chemical Properties



Reactivity w/ acid
Flammability
Reactivity w/ oxygen
Identifying Elements by Their
Properties Examples


Density 8.9 g/cm3
Conducts thermal
energy
Example: Iron

Reacts slowly w/ oxygen in air to form rust
Example: Sodium

http://www.youtube.co
m/watch?v=Mx5JJWI2
aaw&feature=related

Sodium quickly oxidizes in air
and is violently reactive with
water, so it must be stored in an
inert medium, such as kerosene.
Elements Are Classified By
Their Properties
Think Dogs
 All dogs have similarities but aren’t exactly
alike

Elements are grouped In
Categories
Metals
 Nonmetals
 Metalloids

Metals



Shiny
Good Conductors
Malleable- they can be bent
without breaking

Ductile

they have a high density (they
feel heavy for their size)
they make a ringing sound
when they are hit (they are

sonorous)
Nonmetals

Oxygen, carbon,
sulphur and chlorine

All non-metals have
these properties in
common:



dull
poor conductors of
heat and electricity
(they are insulators)
weak and brittle (they
easily break or
shatter)
Curious carbon
Carbon is a solid non-metal that exists in two very different forms.
These are diamond and graphite. The table shows some differences between them.
Diamond
Graphite
transparent and
colourless
opaque and black
does not conduct
electricity
conducts electricity
hard
soft
Diamond is the hardest natural substance on Earth,
but it is also very brittle and will shatter if hit with a hammer.
Graphite is unusual because it is a non-metal that conducts electricity.
The Metalloids







Boron
Silicon
Germanium
Arsenic
Antimony
Tellurium
Polonium




Have properties of
metals and nonmetals
Shiny/Dull
conduct heat and
electricity better than
nonmetals but not as
well as metals
their shape is easily
changed
Compounds
Most elements easily take part in chemical
reactions
 Compound- pure substance composed of
two or more elements that are chemically
combined

Familiar Compounds

http://www.nelsonthornes.com/secondary/science/scinet/scinet/elements/compound/conte
nt.htm
Magnesium+ O2=Magnesium
Oxide

In order for elements to combine they must
react or undergo chemical change with one
another
http://jchemed.chem.wisc.edu/JCESOFT/CCA/CCA3/STHTM/MAGAIR/MAGAIR.HTM
Magnesium
metal
...is burned in
air
forming
magnesium
oxide
Elements Combine in a Definite
Ratio to form a Compound
Compound are not random
 Elements join in specific ratio

Water H2O
 1g Hydrogen +8g Oxygen
 1:8
 If ratio is change substance changes

Every Compound Has a
Unique Set of Properties

Physical



Melting Pt
Boiling Pt
Density

Chemical

Reactivity
Table Salt
=
A yellow toxic gas
extremely irritating
to the eyes and
mucous membranes
Soft white metal
that reacts
violently with
H2O
NaCl
Question 2pt

Do the properties of pure water from glacier
and from a desert oasis differ?
Due in 5 min Only
Compounds Can Be Broken Down
into Simpler Substances
Chemical reaction separate compounds
 Examples

Mercury Oxide + Heat = Mercury + Oxygen
 Melted Table Salt + Electric Current = Sodium +
Chlorine

Compounds can not be broken
down by Physical Changes

Filtration or grounding a solid into a powder
will not change the compound
Compounds in Your World

Nature




Proteins
Nitrogen Compounds
Carbon Dioxide
Sugar

Industry




Ammonia
Medicines
Food Preservatives
Synthetic Fabrics
Properties of Mixtures

Mixture- a combination of two or more
substances that are not chemically
combined
Mixtures
Each substance retains Identity
 Can be physically Separated
 Components don’t have a definite Ratio

Common Technique for
separating Mixtures

Distillation ( separation based on boiling pt)
Magnet

Example: separating iron filings from
sand
Centrifuge

Separates by density (higher density sinks to bottom)
Filtration

Example: Separating dirt from water by
filtering
Evaporation



Example: Getting salt out of salty water
The salty water is put into an evaporating basin (or any
shallow dish such as a saucer).
It is left in a warm place and the water evaporates leaving
behind the salt crystals.
Mixture Vs Compound
Components
Components
Formed
Mixtures
Compounds
Elements and
Compounds
Keep original
properties
elements
Using any ratio
Using a set ratio
Separated By Physical
Lose original
properties
Chemical
Solutions

Solution- a mixture that appears to be a
single substance but is composed of
particles of two or more substances
 Homogeneous
Mixtures

Homogeneous

solution that has the
same appearance and
properties throughout
the solution

Heterogeneous

mixtures do not appear
to be the same
throughout
Solutions



Solvent – the
substance in which the
solute is dissolved
Solute – The
substance dissolved
Water universal solvent
Solutions

Soluble

Able to dissolve

Insoluble

Unable to dissolve

The substance that dissolves to form a
solution is the __________.
Solute
FIGURE 11.1 Soluble and insoluble. Alcohol is
soluble in water; when added to water, it forms a
clear solution. Oil is insoluble in water; when
added to water, the two liquids form separate
layers.
Saturated Solutions

Equilibrium in solutions: the equilibrium in a sucrose
solution between dissolved and undissolved
molecules; the equilibrium in an ionic solution between
dissolved ions and undissolved sodium chloride.
Solutions
Substances
Solvent
2 Gases
Gas with Greater
volume is
solvent
Liquid w/
Greater volume
is solvent
Liquid is
2 Liquids
Liquid +Solid
Examples of Different States
in Solutions
Gas in gas
Dry air (oxygen in nitrogen)
Gas in Liquid
Soft Drinks (CO2 in Water)
Liquid in Liquid
Antifreeze
Solid in Liquid
Salt water
Solid in Solid
Brass (Zinc in copper)
Concentration: How much
solute dissolved in solvent
Measured in grams of solute per mL of
solvent
 Dilute
 Concentrated


A solution that contains a large amount of
solute is best described as?

concentrated
Solubility
The amount of solute needed to make a
saturated solution
 Grams of solute per 100mL

What affects How Quickly
Solids Dissolve in Liquids
Mixing (shaking)
 Heating
 Crushing

Lets Think

The amount of solute needed to form a
saturated solution is the __________ of the
solute.

Solubility
Which types of water contain
dissolved minerals?
Cleaned puddle
Distilled water
water
Which of these beakers will have dissolved materials in them? You
must give a reason for your prediction and then you need to explain
how you can test your prediction
Tap water
Sea water
In your explanation you may find some of the following words useful:
Dissolved
Evaporate
Solid
Beaker
Unit 6C: L.O. 3,4,5
Solution
Filter
Heat
I
More dissolving
Stir
Add sugar
Add coffee
Stir
Which of the substances has dissolved?
Unit 6C: L.O. 4
D
What happens when a solution is
evaporated?
Cold tile
Condense
Evaporate
Salty water
Heat
Will the steam which
condenses on the
cold tile be salty?
Unit 6C: L.O. 6
D
Suspensions

A mixture in which particles of material are
dispersed throughout a liquid / gas but are
large enough to settle out
Heterogeneous- components are easily seen
 Particles are Large (to heavy to remain in
suspension)

Colloids

A mixture in which particles are dispersed
throughout but are not heavy enough to
settle on there own

A _________ can be separated by filtration.

suspension
Mixtures
Solutions
Colloids
Suspensions
Compounds