L2 Chemistry Essay

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CHEM1002 Lecture 2

Chemical symbols of the elements

Recap: Types of Particles

• One or two letters, the first is always uppercase and the second always lowercase.

• An atom is a chemically indivisible particle of an element.
• An element contains atoms of only one type.
(eg. H, O, C)
• A molecule of a substance consists of two or more atoms
• A compound is composed of more than one type of element joined by chemical bonds.

C carbon
Ca calcium
P phosphorus
Fe iron -ferrum
Pb lead - plumbum
1

2

Chemical equation represents a change of one substance to another.

Formula represents atoms present

Methane + oxygen
Methane, CH4

carbon dioxide + water

Ammonia, NH3

Alcohol, CH3CH2OH
3

CH4

+ 2 O2

CO2

+

2 H2O
4

1

CHEM1002 Lecture 2







Colour
Melting point
Conductivity
Density
Surface tension

Toby Hudson, (School of Chemistry, University of Sydney)

Physical properties are the properties that a substance shows by itself, without changing or interacting with another substance

• Different states of a substance are different physical ways of packing its component particles.
• A physical change is associated with a change of state.
• A chemical change involves changing one substance into another.

1 L Br2
1 L Hg

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Chemical Properties

Toby Hudson, (School of Chemistry, University of Sydney)

Physical Properties

States of Matter

6

Physical vs Chemical

Chemical properties are the properties of a substance that result in the formation of a new substance – Flammability
– Corrosiveness
– Reactivity with acid

Physical changes occur when a substance alters its physical form but NOT its composition
– the compound doesn’t change
– chemical bonds don’t form or break
– e.g.: boiling of water, freezing of wax

Chemical changes occur when a substance (or a number of substances) is converted into a new substances
– the compound/allotrope changes
– chemical bonds form or break
– e.g.: burning of H2 with O2 to give H2O, reacting zinc in hydrochloric…