Unit 1. Carbon and its inorganic compounds
Key unit competence
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Relate the properties of carbon and its compounds to its uses
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Describe how some of the compounds of carbon are prepared.
Unit learning objectives
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Name the allotropic forms of carbon and relate its properties to its uses.
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Explain the properties of carbon and its compounds.
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Explain the impact of carbon compounds on the environment.
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Explain the carbon cycle and relate it to food chains.
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Explain the causes of hard water.
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Prepare, collect and test for CO2.
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Prepare, collect and test the carbonates of different metals.
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Appreciate the importance of natural resources.
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Develop self-confidence during presentations.
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Develop a culture of working together in groups.
Unit outline
1.1. Allotropic forms of carbon, their physical
properties and uses
1.2. Chemical properties of carbon
1.3. Preparation, properties and uses of carbon dioxide
1.4. Preparation, properties and uses of carbonates
and hydrogen carbonates
1.5. Environmental issues of carbon dioxide and
carbon monoxide
1.6. Hard water and soft water
1.7. The carbon cycle
1.8. End unit assessment
Lesson 1.1. Allotropic forms of carbon, their physical properties and uses
Lesson learning objectives
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Define allotropy and allotropes
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Name allotropic forms of carbon
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Differentiate diamond and graphite
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Appreciate the importance of carbon allotropes
What is allotropy and allotropes ?
Allotropy is the existence of an element in more than one form in the same physical state.
Allotropes are different forms of an element that exist in the same physical state.
Allotropes have same chemical properties but different physical properties
What are the two types of allotropes of carbon?
Allotropes of carbon can be classified broadly into two types:
.Crystalline forms
.Non-crystalline or amorphous forms
1.A. Crystalline allotropes of carbon: Diamond
Structure of diamond
In diamond, each carbon atom is covalently bonded to four other carbon atoms giving a regular tetrahedron shape.
Thus, all the four valence electrons in diamond are used in the bonding.
What are the Physical properties of diamond?
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It is the hardest naturally occurring substance. This is because of the strong covalent bonds that hold the atoms of carbon together.
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It is a colourless crystalline and transparent with a dazzling brilliant lustre. The lustre is caused by its high refractive index.
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Diamond has a higher density of 3.5g/cm3 compared to that of graphite (2.25g/cm3).This is because the arrangement of atoms in a diamond crystal allows for more atoms to be packed per given space compared to graphite.
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It has a high melting and boiling points. It melts at 4200°C. This is because all the carbon atoms are bonded by very strong covalent bonds that require a lot of heat energy to break.
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Diamond does not conduct electricity. This is
because it has no delocalized electrons.
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Diamond is a good conductor of heat because of its strong covalent bonding.
What are the important uses of diamond?
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Because of its hardness, it is used for making drill tips used when drilling or cutting metals. It is also used to make glass cutters.
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Used in making jewellery due to its beautiful sparkling radiance and lustre.
1.B. Crystalline allotropes of carbon: Graphite
Explain why it contains delocalized electrons?
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In graphite, each carbon atom is covalently bonded to three other atoms while the fourth electron is
delocalized; means it is not attached to any particular atom but belongs to the entire structure.
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These delocalized electrons are free to move through the graphite structure.
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Graphite exists in hexagonal layers of carbon atoms. The layers are held together by weak Van der Waal’s forces of attraction, and this makes them slide easily over each other.
How can you relate the properties of graphite to its uses?
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It is used as electrodes in dry cells and fuel cells. This is because it is a good conductor of electricity.
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It is used to make pencil ‘leads’ when mixed with clay. This is due to the sliding of its layers which enable it to slide on paper when writing.
What are the physical properties of Graphite?
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Graphite is a soft, black and shiny material with a greasy feel.
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Graphite easily flakes off.
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Has relatively high melting and boiling points due to the strong covalent bonds joining its atoms together.
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It has a density of 2.25g/cm3.
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Graphite is a good conductor of electricity due to the presence of delocalized electrons in its structure.
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It is opaque. Numerous parallel layers arranged on top of one another blocks light from penetrating through.
How can you relate the properties of graphite to its uses?
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Graphite is used as a carbon raiser in the production of steel. It gives steel its strengthening characteristics.
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It is used in advanced high-friction applications such as car brakes and clutches because of its high thermal and electrical conductivity.
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At high temperatures, graphite can be used as a lubricant in place of grease or oil. This is because graphite has a high boiling point.
How can you relate the properties of graphite to its uses?
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It is useful in the production of paints and shoe polish, where the powdered form of lump graphite is used due to its natural water-repellent property. It is the best choice for giving a protective coating on wood or shoe leather.
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It is used to make furnace linings, brushes for electric motors and generators.
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It is used as a moderator in nuclear reactors.
Property |
Graphite |
Diamond |
Structure |
Hexagonal |
Tetrahedral |
Appearance |
black, opaque, slippery solid |
colourless, transparent, crystalline solid |
Electrical conductivity |
Good |
Poor |
Solubility |
Insoluble in water and organic solvents |
Insoluble in water and organic solvents |
Hardness |
soft and slippery |
Extremely hard |
2. Non-crystalline (amorphous) allotropes of carbon
How are amorphous form of carbon obtained?
Non-crystalline forms (amorphous forms) of carbon are formed by decomposing other substances like wood using heat.
Arrangement of atoms in these forms is not orderly.
These allotropes do not have any particular shape.
Amorphous means without a definite shape
Example of amorphous forms of carbon are: charcoal, coke, soot, coal and lamp black.
2.A. Charcoal
What are the physical properties of charcoal?
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It is a black, porous and brittle solid
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It is soft and has low density.
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Bad conductor of electricity.
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It can adsorb large volume of gases and solids.
Based on their sources, suggest three types of charcoal.
There are three common types of charcoal : wood charcoal, animal charcoal and sugar charcoal.
2.A.a. Wood charcoal
How is wood charcoal obtained?
Wood charcoal is obtained when wood is strongly heated in absence of air. This process is called destructive distillation of wood.
wood charcoal
What are the uses of wood charcoal?
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Household fuel for cooking
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Reducing agent in extraction of metals
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constituent of gun powder (explosives in guns and rifles)
2.A.b. Animal charcoal (bone charcoal)
How is animal charcoal obtained?
Animal charcoal is formed when bones are subjected to destructive distillation.
What are other compounds found in animal charcoal?
Animal charcoal is only about ten percent carbon with the rest being mainly calcium phosphate.
Watch the following video and describe one way by which sugar charcoal is formed.
click her e to watch the video
Answer
Sugar charcoal is obtained by dehydrating sugar using concentrated sulphuric acid. This can also be formed by heating sugar in limited supply of air.
What are the uses of sugar charcoal?
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Reducing agent in extraction of metals such as iron and zinc from their oxides
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Decolourizes coloured solutions
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Manufacture artificial diamond
What do you understand by activated charcoal?
Activated charcoal is the charcoal that is finely powdered. It is used to remove smelly gases in slaughter houses, gas manufacturing plants, large air conditioning systems and airports. This is because activated charcoal has a large surface area and hence can adsorb large volumes of gases.
2.B. Lamp black / soot
Why the inside of your school kitchen chimney is black ?
The inside of chimney is coated with a very fine black powder of carbon known as soot.
What are the use of soot?
-Making black shoe polish, black ink, black paints and carbon paper
-As an ingredient in the rubber tyres (for hardening of rubber).
2.C. Coke
What is coke and how is it prepared?
It is a solid made by heating coal in the absence of air in the process known as destructive distillation of coal.
What are the properties of coke?
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Porous and black
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Burns with almost no smoke