LFS103 Lecture Notes - Lecture 1: Magnesium, Unified Atomic Mass Unit, Chlorine
LFS103
WEEK 1
1.1 Classification of Matter
Matter: Anything that has mass and occupies space.
Pure substance: Mass that has a fixed or definite composition. There are two kinds:
Elements: Composed of only one type of atom.
Cannot be broken down into simpler substances
E.g. silver atom, iron atom, aluminium atom
Compounds: Consists of two or more elements combined in the same proportion.
Held together by attractions called bonds, which form small groups called molecules
Can be broken down into constituent elements by chemical, but not physical means.
Mixtures: Two or more different substances are physically mixed, but not chemically combined.
There are two classifications:
Homogeneous mixture (solution): the composition is uniform throughout the sample.
E.g. air (oxygen and nitrogen gas), sea water (solution of salt and water)
Heterogeneous mixture: components do not have a uniform composition throughout the
sample.
E.g. oil and water
Separation methods of mixtures:
Solids separated from liquids by
filtration pouring mixture through filter
paper in a funnel.
Chromatography:
different
components of a
liquid mixture
separate as
they move at
different rates up
a piece of chromatography
paper.
States of matter
Types of matter:
Solid: definite shape and volume
Liquid: definite volume but not shade
Gas: does not have definite shape or volume
Properties and Changes
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The state of a particular type of matter depends on its:
Temperature
Surrounding pressure
The forces holding its structure together
Physical Chemical
Physical properties: characteristics that can be
observed or measured.
E.g. shape, colour, melting point, boiling point and
physical state of a substance.
Physical changes: when the appearance of a
chemical substance is altered, but not its
composition.
E.g. Water has a different appearance to ice but it is
still H2O.
Chemical properties: describe the ability of a
substance to undergo a composition change.
Chemical change: when the reacting chemical
substance changes into new chemical substances
that have different formulas and properties.
Example: In rain iron (Fe) reacts with oxygen (O2) to
form rust (Fe2O3).
Fe and O2 Fe2O3 = chemical change
Rust is the new substance with new
physical and chemical properties
Matter undergoes a change of state when it is converted from one state to another.
Melting and Freezing
Melting: When heat is added to a solid, the
particles move faster. When the particles
separate and move about in random patterns,
changing it from a solid to a liquid.
Freezing: When the temperature of a liquid is
lowered kinetic energy is lost so the particles
slow down and the attractive forces pull the
particles close together.
Vaporisation and Condensation
Vaporisation
Evaporation: Takes place as water molecules with
sufficient energy escape from the liquid surface and enter
the gas phase
Boiling: gas bubbles form and escape from liquid
Condensation: Water vapour is converted back to liquid as the
water molecules lose kinetic energy and slow down
Sublimation and deposition
Sublimation: The particles on the surface of a solid change
directly to a gas with no temperature change.
Deposition: Gas particles change directly to a solid
find more resources at oneclass.com
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Document Summary
Matter: anything that has mass and occupies space. Pure substance: mass that has a fixed or definite composition. Elements: composed of only one type of atom. Cannot be broken down into simpler substances. E. g. silver atom, iron atom, aluminium atom. Compounds: consists of two or more elements combined in the same proportion. Held together by attractions called bonds, which form small groups called molecules. Can be broken down into constituent elements by chemical, but not physical means. Mixtures: two or more different substances are physically mixed, but not chemically combined. Homogeneous mixture (solution): the composition is uniform throughout the sample. E. g. air (oxygen and nitrogen gas), sea water (solution of salt and water) Heterogeneous mixture: components do not have a uniform composition throughout the sample. Solids filtration paper in a a piece paper. Gas: does not have definite shape or volume separated from liquids by pouring mixture through filter funnel.
