4. Sulphur trioxide, SO3, will also form when sulphur dioxide, SO2, reacts with oxygen, O2,
gas in air.
5. When sulphur trioxide, SO3, dissolves in rainwater, sulphuric acid, H2SO4, is also formed
causing acid rain.
6. The effects of acid rain on the environment are as follows:
- Corrodes and destroys property such as bridges, buildings and statues
- Reduces pH of soil and causes it to be unsuitable for plant life
- Reduces pH of water and causes the death of aquatic life
- Destroys the beauty of the environment such as the collapse of limestone caves
- Manufacture of Ammonia and its salt
Uses of Ammonia
Ammonia, NH3, has many uses in our daily life. A few examples are:
-
Manufacture of nitrogenous fertilisers such as ammonium phosphate, (NH4)3PO4
-
Manufacture of nitric acid, HNO3 through the Ostwald process
- Manufacture of electrolytes in dry cells
- Manufacture of cleaning agents such as washing powder and detergents
- Manufacture of explosives such as trinitrotoluene (TNT)
- Manufacture of dyes
Properties of Ammonia
Properties of ammonia are summarised as follows:
Properties of ammonia
Manufacture of Ammonia
1. Ammonia, NH3, is manufactured on a large scale in factories through the Haber process.
2. In the Haber process, nitrogen, N2, and hydrogen, H2, gases are mixed in the ratio of 1:3
volumes (or moles).
3. The hydrogen, H2, gas is obtained from the methane, CH4, a type of natural gas while
nitrogen, N2, gas is obtained from air by fractional distillation of liquified air.
4. The gas mixture is passed over iron (catalyst) at a temperature of 450-550 ºC and
compressed under a pressure of 200-500 atmosphere.
5. The ammonia, NH3, gas obtained is cooled (temperature of -50 ºC) to become liquid ammonia NH3(l).
Haber process for the manufacture of ammonia, NH3
- Alloys
Arrangement of atoms in pure metal
1. Pure metal is soft and not very strong
2. Atoms of a pure metal have similar size and shape and are arranged closely but there is still
space between atoms.
3. When force is applied to pure metals, the atoms slide along one another easily.
4. This property causes pure metals to be ductile, that is, it can be stretched into a wire.
5. When knocked or hammered, metal atoms slide along one another to fill the spaces
between the metal atoms.
6. This property causes pure metal to be malleable, that is, it can be knocked or pressed into
various desired shapes.
Pure metal is soft and not very strong
Alloy
1. An alloy is a compound formed from a mixture of metal and other elements.
2. The impurity atom (foreign atom) may be atoms of other metals or non-metals such as
carbon.
3. The process or mixing atoms of impurities with atoms of pure metal by melting is called
alloying.
4. The aims of alloying are to:
- Increase the strength and hardness of the metal
- Prevent corrosion of the metal
- Improve the appearance of the metal so that it is more attractive
Examples of alloys and their components
Arrangement of atoms in alloys
1. Impurity atoms which are mixed may be larger or smaller than atoms of pure metal.
2. Impurity atoms fill the empty spaces between the atoms in pure metal.
3. Impurity atoms can prevent the layers of metal atoms from sliding along one another
easily.
4. Due to this, an alloy is harder and stronger than pure metal.
5. For example, steel is harder than iron.
Movement of pure metal atoms disrupted due to the presence of impurity atoms
Uses of alloy
- Synthetic Polymers and their uses
1. Polymers are long chains of molecules made from combinations of many small
molecules.
2. Small molecules that combine to form polymers are called monomers.
3. Polymerisation is a process of combining monomers to form long chain of molecules.
4. Polymers can be divided into two types which are natural polymers and synthetic
polymers.
Natural polymer
1. A natural polymer is a polymer that occurs naturally.
2. Natural polymers are normally made by living organisms.
Synthetic polymer
1. Synthetic (artificial) polymers are man-made polymers that are produced from chemical
compounds through polymerisation.
2. Plastic, synthetic fibres and synthetic rubbers are three examples of synthetic polymers.
3. There are two types of polymerisation which are:
- Addition polymerisation
- Condensation polymerisation
- The uses of Glass and Ceramics
Types, composition, characteristics and uses of glass
1. The main component of glass is silica or silicon dioxide, SiO2, which is obtained from
sand.
2. The main characteristics of glass are:
- brittle
- hard
- chemically inert
- transparent
- not permeable to gas and liquid (fluid)
- does not conduct electricity
- heat insulator
3. The most simple glass is the fused silica glass. This mainly contains silica, SiO2.
4. Most of the glasses are produced by mixing molten silica, SiO2, with other compounds.
5. Glass can be recycled. Glass can also be melted and solidified repeatedly.
6. Different types of glass has different uses.
Use of glass
- The uses of Composite Materials
1. In this modern world, the demand for items with specific properties is high.
2. Compounds with specific properties are combined to produce a composite material that
meet the requirements of industry, construction and transportation.
Composite materials
1. Composite materials are produced from the combination of two or more different
compounds such as alloys, metals, glass, polymers and ceramics.
2. The characteristics of the produced material are much more superior than those original
components.
3. Several uses of composite materials are:
- Reinforced concrete
- Superconductor
- Fibre glass
- Fibre optics
- Photochromic glass
- Ceramic glass
- Plastic strengthened with glass fibres
Fibre optics
