Download IGCSE Chemistry Notes PDF

TitleIGCSE Chemistry Notes
TagsIon Chemical Bond Acid Radioactive Decay Covalent Bond
File Size4.1 MB
Total Pages46
Table of Contents
                            Collisions
Changing the temperature
Changing the concentration or pressure
Changing the surface area
Effect of catalysts
                        
Document Text Contents
Page 2

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



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Page 23

The difference between strong and weak acids
In solution of strong acids, all molecules become ions.

In solution of weak acids, only some do.

The higher the concentration of hydrogen ions, the lower the pH, the stronger the acid.

Alkaline solutions contain hydroxide ions, this is what makes them alkaline.

Alkalis produce hydroxide ions

In solution of strong alkali, it contains more hydroxide ions.

The difference between a strong alkali and weak alkali

In solution of weak alkali, it contains less hydroxide ions.

The higher the concentration of hydroxide ions, the higher the pH.

To tell if the solution is a weak or strong acid. You can also measure there conductivity.
A strong acid will show high conductivity and low pH. A weak acid does not conduct well,
and has a higher pH.

For alkali’s, a strong alkali will show high conductivity and high pH. A weak acid will
show low conductivity and low pH.

Reaction of acids with metals

When an acid reacts with a metal, hydrogen is displaced, leaving a salt in solution. It’s a
redox reaction.

Reaction of acids with bases

Bases

1. With alkalis

are a group of compound that reacts with acids, and neutralize them, giving a salt
and water. Bases include alkalis, and insoluble metal oxides, hydroxides and
carbonates.

Acid + alkali  salt + water

2. With metal oxides

Acid + metal oxide  salt + water

3. With carbonates

Acid + metal carbonate  salt + water + carbon dioxide

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Page 24

1. Neutralizing acids, giving salt and water. With carbonates carbon dioxide is
produce too.

Reactions of bases

2. All the alkalis (except ammonia) will react with ammonium compounds, giving
ammonia out.

An ionic equation shows only the ions that actually take part in a reaction. It leaves out
the rest.

The ionic equation

1. First write down all the ions present in the equation
2. Now cross out any ions that appear, unchanged, on both sides of the equation
3. What’s left is the ionic equation for the reaction

Acids donate its protons to bases and bases accept them.

Proton donors and acceptors

For example:

Magnesium oxide is a insoluble base. The acid donates its H+ protons and the oxygen
from magnesium oxide react with it to make water molecules.

Most crops grow best when the pH of the soil is near 7. If soil is too acidic or too alkaline,
crops grow badly or not at all.

Acidity in soil

Usually acidity is the problem. Why? Because of a lot of vegetation rotting in it or
because too much fertilizer was used in the past.

To reduce the acidity, the soil is treated with a base like limestone or quicklime or slaked
lime.

Acid rain is caused by factories, power stations, homes who burn fossil fuels to make
electricity. The waste gases from all these reactions include sulphur dioxide, and oxides
of nitrogen. They go into the air and react with air and water to produce sulphuric acid
and nitric acid which are strong acids.

Acid rain







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Page 46

Unit 17: Organic chemistry


Organic chemistry is a branch of chemistry connected with
compounds of hydrogen and carbon (hydrocarbons).

Hydrocarbons

It is a class containing only hydrogen and carbon bonded together
covalently. They can form very long chains, and can form chains
linked by one double bond or triple bond. Hydrocarbons are devided
into two groups Alkanes C-C & Alkenes C=C

Naming of organic substances







Alkanes

General molecular formula = Cn H2n+2

The alkanes are a homologus series which means that all of the
compound have the same

• functional group
• same general formula
• same chemical properties
• show a gradual change in chemical properties
• Khalid mafee zeb







1C -> meth 3C -> prop 5C -> pent 7C-> hept

2C -> eth 4C -> but 6C -> hex 8C -> hex

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