Unlock the secrets of chemistry with our comprehensive IGCSE O Level Chemistry book! Packed with easy-to-understand explanations, engaging visuals, and hands-on activities, this book will help you master the fundamentals of chemistry and achieve top grades in your exams. From atomic structure to ch...
By: Abdulla Al Zaabi
Refined and cleared by KmQ! :D
, Unit 1: States of matter
Everything is made of particles. Particles in solid are not free to move around. Liquids
and gases can. As particles move they collide with each other and bounce off in all
directions. This is called random motion.
In 2 substances, when mixed, particles bounce off in all directions when they collide.
This mixing process is called diffusion. It’s also the movement of particles without a
force.
The smallest particle that cannot be broken down by chemical means is called an atom.
·In some substances, particles are just single atoms. For example the gas argon, found
in air, is made up of single argon atoms.
·In many substances, particles consist of 2 atoms joined together. These are called
molecules.
·In other substances, particles consist of atoms or groups of atoms that carry a charge.
These particles are called ions.
Solids liquids and gases
Solid Properties:
• Definite shape and volume
• Normally hard and rigid
• Large force required to change shape
• High Density
• Incompressible
Model:
• Closely packed
• Occupy minimum space
• Regular pattern
• Vibrate in fixed position
• Not free to move
Liquid Properties:
• Definite volume but no shape.
• High Density
• Not compressible
Model:
• Occur in clusters with molecules slightly further apart compared to solids
• Free to move about within a confined vessel
,Gas Properties:
• No Fixed volume and no fixed shape
• Low density
• Compressible
Model:
• Very far apart
• Travel at high speed
• Independent and random motions
• Negligible forces of attraction between them
Diffusion in Gases
Gases diffuse in different rates. Those rates depend on their factors:
1. Mass of the particles
The lower the mass of its particles the faster a gas will diffuse.
Why?
Because the lighter the molecules...the faster it will travel (obviously...)
2. The temperature
The higher the temperature, the faster a gas will diffuse.
Why?
Because particles gain energy as they are heated
Mixtures, Solutions, and Solvents
Mixture: Contains more the one substance. They are just mixed together and not
chemically combined.
Example: Sand and water.
Solution: It is when a solute and a solvent mix. The solute dissolves in the solvent
making a solution.
Example: sugar (solute) dissolves in water (solvent) making a solution of sugar
and water.
The solubility of every substance is different.
To help a solute dissolve you could:
• Stir it
• Rise the temperature
If you add excess amount of sugar in a small amount of water...it won’t dissolve as there
is no space for it. The solution becomes saturated.
Solvent: A substance that allows solutes to dissolve in
Example: Water, Ethanol
, Pure substances and impurities
A pure substance is a substance that has no particles of any other substance mixed with
it.
An unwanted substance, mixed with a wanted substance, is called an impurity.
To check if a substance is pure, you have to check its melting and boiling points.
A pure substance has a definite, sharp, melting point. When a substance is impure, the
melting point falls and its boiling point rises. So the more impurity present, the wider and
bigger the change in melting and boiling point.
Separation methods:
Filter ------------------------- Solid from liquid
Centrifuge ------------------ Solid from liquid
Evaporation ---------------- Solid from its solution
Crystallization -------------- Solid from its solution
Distillation ------------------ Solvent from a solution
Fractional distillation ----- Liquid from each other
Chromatography ---------- Different substances from a solution
Separation methods
1. Filtering
Example:
A mixture of chalk and water...
1. A filter paper is placed in a funnel, the funnel placed on a flask.
2. The mixture is poured on the filter paper.
The chalk (the residue) will remain in the filter paper and the water (the filtrate) will fall
down in the flask.
2. Centrifuging
This method is used to separate small amounts of solid and liquid. Inside a centrifuge
(it’s a machine), test tubes are spun very fast so the solid gets flung to the bottom.
3. Evaporation
This method is used to separate a solution in which the solid is dissolved in the liquid.
1. The solution is heated so that the liquid evaporates and the solid remains in the
bottom of the evaporating dish.
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