Chemical vs Physical Properties

Chemical vs. Physical Properties

University of Lincoln
presentation

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Increasing metallic character
The periodic table
Increasing metallic character

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Metals
Metalloids
Nonmetals


Properties of Matter

• Types of matter are distinguished by their properties

• There are two categories of properties that concern us:

– Physical properties
– Chemical properties

• If two samples of matter have the same
properties, they must be the same substance



• Understanding the properties of compounds is
important for:

– Identifying an unknown substance
– Distinguishing between different substances
– Characterising a newly discovered substance
– Predicting the usefulness of a substance for a
specific application



• Physical properties –the identifying characteristics of
matter
– Some properties can be readily measured with our senses
• odour
• Colour

– Instruments are needed to measure other properties
• electrical resistivity
• compressibility
• hardness
• melting point
• radioactivity



• Chemical properties – describe the reactivity of a
substance towards other substances

– Ethanol burns in air (reacts with oxygen)
– Sodium reacts vigorously with water
– Corrosion of metal parts (rust)
– Trinitrotoluene (TNT) is explosive
– Lysergic acid diethylamide (LSD) is an hallucinogenic drug


Physical properties
• METALS • NON METALS
– good conductors of – poor conductors of
electricity electricity
– Ductile – not ductile
– malleable, lustrous – not malleable
– typically: solid – solid, liquid or gas
– high melting point – low melting point
– good conductors of – poor conductors of
heat heat


Chemical properties

• METALS • NON METALS
– react with acids – do not react with acids
– form acidic oxides
• react with bases
– form basic oxides
• react with acids – form anions
– form cations – form covalent halides
– form ionic halides


The Rubber Book


Ethanol
Stoichiometry = C2H6O
Melting Point = -115 ºC Dimethyl Ether
Boiling Point = 78 ºC Stoichiometry = C2H6O
Density = 0.79 g/cm3 Melting Point = -140 ºC
Boiling Point = -24 ºC
Density = Gas
Ethylene Glycol
Stoichiometry = C2H6O2
Melting Point = -16 ºC
Boiling Point = 197 ºC
Density = 1.11 g/cm3


Mixtures

• Homogeneous Mixture – composition and
properties are uniform (sometimes called a
solution)

– Air – principal components include O2, N2 & CO2
– Vodka – principal components are EtOH & H2O
– Brass – solid solution of Cu and Zn
– Ruby – solid solution of Al2O3 and Cr2O3


Mixtures

• Heterogeneous Mixture – composition and
properties are non-uniform

– Chocolate Chip Cookie – chocolate, sugar, dough, etc.
– Concrete – cement, sand, aggregate
– Vomit – Depends upon previous intake of food and
drink


Mixtures, Compounds & Elements
Matter

No Yes
Is it uniform
throughout?

Heterogeneous
Homogeneous
mixture

No Does it have a Yes
variable
composition?
Pure substance
Homogeneous
mixture (solution)
No Can it be separated Yes
Into simpler
Substances?
Element Compound


Mixtures, Compounds & Elements

Molecules
Atoms of of an
an element
element

Na N2

Molecules Mixture of
of a elements
compound and a
compound

SO3 Mixture

Changes in Matter

• Physical change
– Substance changes physical appearance without
altering its identity
e.g. changes of state
ice melting to form water


Changes in Matter

• Chemical changes (or chemical reactions)
– Substances transform into chemically different
substances
i.e. identity changes
e.g. decomposition of water


Changes in Matter
• Chemical • Physical

Gas

Melting
Solid Liquid
Freezing


Solubility
• Defined as:
– The quantity of a particular substance that
can dissolve in a particular solvent (yielding a
saturated solution)
– Can be expressed in g/100g of water, mol dm-
3

• Generally refers to the compound’s ability
to dissolve in water
– the aqueous phase (aq)


Solubility

• A saturated solution
– contains the
maximum amount of
solute that can
dissolve
– undissolved solute
remains


Solubility

• An unsaturated
solution
– does not contain all
the solute that could
dissolve


Solubility
Rule 1
Exceptions
ALL
Silver nitrite and
nitrate (NO3-) potassium perchlorate
nitrite (NO2-) are considered only
chlorate (ClO3-) and slightly soluble
perchlorate (ClO4-)
salts are soluble


Solubility
Rule 2 Exceptions

ALL
Some Li+ salts are
alkali metal
insoluble
(Li+, Na+, K+, Rb+, Cs+) and
ammonium (NH4+)
salts are soluble


Solubility
Rule 3
Exceptions
MOST
halogen (Cl¯, Br¯, I¯) Ag+, Pb2+, Hg22+,
salts are soluble Cu+, Tl+
(Pb2+ halogens are soluble in hot water)

HgBr2 is only slightly soluble


Solubility
Rule 4 Exceptions

MOST
Ag+, Hg22+
acetate (C2H3O2¯) salts
are soluble


Solubility
Rule 5 Exceptions

MOST
Ca2+, Sr2+, Ba2+, Ra2+, Pb2
sulphate (SO42¯) salts +, Ag+, Hg2+
are soluble
(Some sources consider calcium
sulphate and silver sulphate to be
slightly soluble)


Solubility
Rule 6
Exceptions
MANY
sulphides (S2¯) salts All alkali metal and
are insoluble alkaline earth
(Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+)
sulphides are
soluble

Ammonium sulphide
is soluble
(Some sources consider MgS, CaS
and BaS to be slightly soluble)


Solubility
Rule 7
Exceptions
MOST
borates (BO32-), MgCrO4 is soluble,
carbonates (CO32-),
chromates (CrO42-), MgSO3 is slightly soluble
phosphates (PO43-),
and sulphites (SO32-)
are slightly soluble


Solubility
Rule 8
Exceptions
MOST
hydroxide (OH-) Alkali metal hydroxides
salts are insoluble are soluble

Ba2+, Sr2+, Ca2+, Tl+ are
considered slightly
soluble


Solubility Product Ksp

• In general, the solubility product is the
equilibrium constant for the solubility
equilibrium of a slightly soluble (or nearly
insoluble) ionic compound

(Next Semester)


Temperature & Solubility

FACT: The solubility of a gas decreases with an
increase in temperature

A. Why might a bottle of carbonated drink burst (explode) when
it is left out in the hot sun ?

B. Why do fish die in water that gets too warm?

Based on Daltons Law and Henry’s Law


Corrosion

• Corrosion is the ‘destructive interaction
between a material and its operation
environment’

It leads to material degradation and
contamination of the environment


Corrosion

• Corrosion is a more general term than
‘rusting’ – a concept that only relates to a
homogeneous type of attack
often of iron or steel, in natural environments.


Corrosion
• Non metals can also corrode

• Chemical corrosion
– Removal of atoms from a material by virtue
of the solubility or chemical reaction between
the material and the surrounding liquid


Corrosion by Acid Rain
1908 1969


Biodeterioration

• Can be defined as:

– Any undesirable change in the properties of a
material caused by the vital activities of
organisms


Biodeterioration
• Types:
– physical or mechanical
• material is not a food source
– root damage, gnawing by rodents
– fouling or soiling
• material not damaged
– fungus on shower curtain, barnacles
– chemical assimilatory
• material is used as a carbon and/or energy source
– food spoilage, degradation of fuels, metals
– chemical dissimilatory
• substance not used as carbon and energy source
– acid waste products, tooth decay


Flammability
• A Flammable substance could be defined as
‘having the ability to burn’

• A Flammable liquid can be defined as:
– any liquid having a flash point below 100 F (37.8 oC)
• except any mixture having components with flash
points of 100F (37.8 oC.) or higher, the total of which
make up 99 percent or more of the total volume of the
mixture


Definitions
• Flash Point
– Lowest temperature at which a flammable liquid
exposed to air will burn when exposed to sparks or
flame.
• Auto Ignition Temperature
– Temperature above which spontaneous combustion
can occur without the use of a spark or flame
• Ignition Energy
– Lowest amount of energy required for ignition
• Flammable Liquids
– Liquids with a flash point < 100F (38 oC)
• Combustible Liquids
– Liquids with a flash point > 100F (38 oC)


The Fire Triangle
• Oxidizers • Fuels:
– Gases – Liquids
• Oxygen, fluorine, chlorine • gasoline, acetone,
hydrogen peroxide, ether, pentane
nitricacid, perchloric acid – Solids
– Solids • plastics, wood dust,
• Metal fibers, metal
particles
peroxides,
ammonium
– Gases
• acetylene, propane,
Nitrate
carbon monoxide,
– Liquids Ignition source hydrogen

• Ignition sources
• Sparks, flames, static
electricity, heat


Fire and Forensics
• Accelerant and fire debris analysis
• Fire Modelling
• Smoke Analysis
– Current work at Lincoln
– Characterisation of smoke

• Much, much, more on Fire and Explosion
Investigation in Level 3 !


Acknowledgements
• JISC
• HEA
• Centre for Educational Research and Development
• School of natural and applied sciences
• School of Journalism
• SirenFM
• http://tango.freedesktop.org


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