Dr. Catherine Tan
The Particulate Nature of Matter
(IGCSE Chemistry Syllabus 2016-2018)
Spacing
Energy
Motion
Volume
Shape
Solid
close
Low
Vibrate
Definite
Definite
Liquid
Less close
Moderate
Mobile
Definite
Indefinite
Gas
Far apart
High
Very mobile
Indefinite
Indefinite
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Dr. Catherine Tan
Diffusion
o Spreading of one substance through another from a region of high concentration to region
of low concentration (down the concentration gradient)
o Due to random motion of particles
o Factors that affect the rate of diffusion
- Molecular weight of gas
-
The molecular weight of ammonia is lighter than hydrogen chloride  ammonia will
move faster and further (29.5cm) to react with hydrogen chloride to form ammonium
chloride (white ring)
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