General and Inorganic
Chemistry
Prof. Maurizio Paci
Email: paci@uniroma2.it
Phone: 0672594446
Chemistry and Matter
Chemistry
“The study of properties of materials and of changes that
materials undergo”
Matter
“It’s the physical material of universe; anything that
occupies space and has mass”
Matter can exist in three physical states (aggregation states):
1. Gas o vapor
2. Liquid
3. Solid
Introduction to Matter
Gas
No fixed volume or shape; it conforms to the volume and shape of its container.
Gases can be compressed or expanded to occupy different volumes
Liquid
A liquid has a fixed volume, independent of its container, but it has no specific
shape. It assumes the shape of the container it is in. Liquids cannot be
appreciably compressed
Solid
A solid has its own defined volume and shape. Solids cannot be appreciably
compressed
Introduction to Matter
Substance
A pure substance has a fixed composition and distinct properties. Most matter
we come in contact with in daily life is not a pure substance but a mixture of
different substances
Physical and Chemical Properties
Every pure substance has a unique set of defined properties : characteristics
which allow us to distinguish it from other substances. These properties fall into
two general categories: physical and chemical. Changes can be macroscopic or
microscopic
Chemical Properties – properties that we can measure without changing the
basic identity (the composition)
Chemical Properties – describe the way a substance can change or react to
form other substances
Introduction to Matter
Physical and Chemical Changes
Substances can undergo several changes in properties; these changes can be
classified as either chemical or physical
Physical changes– changing the physical appearance but not the basic identity.
All changes of state (e.g. solid, liqid or gas) are physical changes
Chemical changes– also known as chemical reactions. Changing the basic
identity: the substance is tranformed into different chemically substances .
Introduction to Matter
Mixtures
Mixtures refer to combination of two or more pure substances in which each
substance retain its own chemical identity and hence its own properties
Heterogeneous mixtures are not uniform throughout the sample and have
regions of different appareance and properties
Homogeneous mixtures are uniform throughout the sample, however the
individual substances retain their individual chemical and physical nature.
Homogeneous mixtures are also called solutions. The most common type is
descrbed by a solid (the solute) that is dissolved in a liquid (the solvent)
An important characteristic of homogeneous mixtures is that individual
components retain their chemical and physical properties. Thus, it’s possible
to separate the substances based on their different physical properties For
example, we can separate water from ethanol using heir different boiling
temperatures in a process known as distillation.
Elements and compounds
Pure substances have an invariable composition and are composed by either
elements or compounds
Elements
Substances that cannot be decomposed into simpler substances by chemical
means
Compounds
Can be decomposed into two or more elements, by which that substance is
constituetd.
Elements and compounds
Elements and compounds
Elements
Elements are the basic substances out of which all matter is composed
• Everything in the worls is made up of only 109 different elements
• 90% of the human body is composed by only three elements: Oxygen,
Carbon and Hydrogen
Elements are known by a common name as well as their abbreviation.
Element
Abbreviation
Carbon
C
Fluorine
F
Hydrogen
H
Iodine
I
Nitrogen
N
Oxygen
O
Phosphorus
P
Sulfur
S
Aluminum
Al
Barium
Ba
Calcium
Ca
Chlorine
Cl
Helium
He
Magnesium
Mg
Platinum
Pt
Silicon
Si
Copper
Cu (from cuprum)
Iron
Fe (from ferrum)
Lead
Pb (from plumbum)
Mercury
Hg (from hydrargyrum)
Potassium
K (from kalium)
Silver
Ag (from argentum)
Sodium
Na (from natrium)
Tin
Sn (from stannum)
Elements and compounds
Compounds
Compounds are substances composed by two or more elements. In a
compound the constituting elements are chemically united and are combined
in a definite proportion by mass.
The observation that the elemental composition of a pure compound is
always the same is known as the law of constant composition ( or the law
of definite proportions).
For example, pure water is composed by two elements, Oxygen and
Hydrogen, at the defined ratio of 11% Hydrogen and 89% Oxygen. In one kg
of water we find 110 g of H and 890 g of O. In 20 g of water there are 2.2 g of
H and 17.8 g of O