Giant covalent molecules show how atoms can bond to create vast, interconnected networks. These structures are called macromolecules. They are held together by strong covalent bonds, which give them unique qualities, such as exceptional strength. Examples include diamonds, graphite and graphene.
This article aims at GCSE Chemistry students and will explore giant covalent molecules and their unique properties. It is suitable for all major exam boards, including AQA. We will list examples and their usage in the world around us. If you need support learning this topic, TeachTutti has qualified GCSE Chemistry tutors to guide you through the material and help you make revision notes.
Giant Covalent Molecules
Giant covalent molecules are structures consisting of a huge number of atoms. These atoms are connected by a covalent bond, creating a continuous network. Giant covalent molecules don't have a set number of atoms and can extend indefinitely. They have a lattice-like bonding pattern, that makes them very strong and stable.
The atoms in giant covalent molecules are bonded in a repeating structure. There are no individual molecules. Examples of giant covalent substances include diamond, graphite, graphene and silicon dioxide. They have unique structures and properties that make them important in a variety of ways:
- Diamond is exceptionally hard and is used in cutting tools.
- Graphite has a layered structure, which makes it a good conductor of electricity. It is also used as a lubricant and in pencils.
- Graphene is a single layer of graphite. It is very strong and conductive. It is ideal for electronics.
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What key feature defines giant covalent molecules?
Properties of Giant Covalent Molecules
Giant covalent molecules have unique properties thanks to their strong covalent bonds and extensive lattice structures.
1. High melting and boiling points
The covalent bonds in these structures are very strong and can only be broken with significant energy. This gives substances like silicon dioxide incredibly high melting and boiling points. They can stay solid even at extreme temperatures.
2. Electrical conductivity
Most giant covalent molecules don't conduct electricity because they lack free electrons or charged particles e.g. silicon dioxide. The exception is graphite and graphene:
- Delocalised electrons move freely between the layers in graphite, making it an excellent conductor.
- Graphene has a single layer of carbon atoms, which conducts electricity.
3. Hardness and strength
Diamonds are exceptionally hard thanks to their rigid lattice structure. They are used in cutting tools and drills. Graphite meanwhile has weak forces between its layers. This makes it ideal for lubricants between its layers are soft and slippery.
4. Insolubility in water
They don't dissolve in water. The strength of their covalent bonds can't be broken down by the polarity of water molecules.
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Why is diamond a poor conductor of electricity and diamond good?
Examples of Giant Covalent Molecules
Diamond
Every carbon atom in a diamond is covalently bonded to four other atoms in a tetrahedral arrangement. This repetitive three-dimensional lattice gives the diamond exceptional strength and rigidity. It is the hardest natural substance on Earth.
- Hardness - The rigid lattice makes a diamond ideal for cutting and drilling tools.
- High melting point - Significant energy is needed to break the bonds.
- Non-conductive - There is no electrical charge carried by electrons as they are all used in bonding.
- It is used in cutting tools, such as diamond-tipped drills and glass cutters. It is also used for jewellery due to its brilliance and durability.
Graphite
Graphite is a form of carbon with a completely different structure from diamonds. Every carbon atom creates three covalent bonds. This creates hexagonal layers that are held together by intermolecular forces. These weak forces allow the atoms to slide over each other easily.
- Electrical conductivity - An electrical current can flow because the delocalised electrons can move freely between the layers.
- Soft and slippery - There are weak forces between the layers, making graphite an excellent lubricant.
- High melting point - Graphite has strong covalent bonds within the layers. Significant energy is needed to break it.
- It is used as a lubricant in machinery, the lead in pencils (the sliding layers leave a mark on the paper) and electrodes in batteries and electrolysis.
Graphene
Graphene is a single layer of graphite. It is also known as a "supermaterial". It is a 2D sheet of carbon atoms arranged in a hexagonal structure, like a honeycomb.
- Strength - It is very lightweight yet 200 times stronger than steel.
- Electrical conductivity - It is adept at conducting electricity because the electrons are delocalised and can move freely.
- Flexibility - It can bend and stretch without breaking.
- It is used in advanced electronics, such as flexible screens. It is also common in nanotechnology and composite materials. Solar cells and high-performance batteries often use graphene.
Silicon Dioxide (Silica)
Silicon dioxide is commonly known as silica. It is often found in nature, especially in sand. It is composed of silicon atoms covalently bonded to oxygen atoms in a repeating three-dimensional pattern. This structure is similar to a diamond.
- High melting point - Silica is very heat-resistant thanks to its strong silicon-oxygen bonds.
- Hard and durable - It has a robust structure that is hard to wear down.
- Non-conductive - There are no free electrons or ions that can carry electrical charge.
- It is used in glass production, such as windows and lenses. It is also used in ceramics, cement and in electronic components, such as semiconductors.
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Why can graphite act as a lubricant?
Applications of Giant Covalent Molecules
Giant covalent molecules have a wide range of applicants in everyday life and industry.
Diamond: Cutting and precision
Diamond is important in industries that require precision and durability due to its famed hardness and ability to withstand high temperatures:
- Cutting tools- Diamond-tipped drills and saws are used to cut through hard materials like rock and metal.
- Polishing and grinding - Diamond abrasives are employed to create smooth surfaces.
- Jewellery - It is associated with luxury and elegance thanks to its brilliance and rarity.
Graphite: Lubrication and conductivity
Graphite is very versatile because it has a layered structure and can conduct electricity:
- Lubricants - Graphite reduces friction in machinery. This is particularly importance in high-temperature environments where lubricants like oil degrade.
- Pencil leads - Graphite layers slide easily off a surface, leaving a mark. This makes it ideal for writing and drawing.
- Electrodes - The conductivity of graphite means it is used in batteries and electrolysis.
Graphene: Revolutionising technology
Graphene has incredible strength, flexibility and conductivity. It is transforming the fields it is applied in:
- Electronics - It is applied in flexible screens, high-speed transistors and wearable devices.
- Energy storage - The performance of batteries and supercapacitors is enhanced with graphene.
- Medical technology - Its biocompatibility makes it useful in drug delivery systems and biosensors.
Silicon Dioxide: Foundations of infrastructure
Silicon dioxide is commonly found in sand. It is essential in construction and technology:
- Ceramics and cement - It provides durability and heat resistance to these materials.
- Glass production - Silica has clarity and strength. It is used in windows, containers and lenses.
- Semiconductors - Silicon dioxide is used as an insulator in electronic circuits.
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Why is graphene a revolutionary material in electronics?
Importance of Giant Covalent Molecules
Giant covalent molecules are significant in scientific and industrial applications due to the relationship between their atomic bonding and material properties.
The connection between structure and properties
The atomic structure in giant covalent molecules leads to the unique properties that make them invaluable, including hardness, electrical conductivity and melting points:
- Diamonds are so hard because of their tetrahedral arrangement.
- Graphite is an effective lubricant and conducts electricity well because its layered structure allows electrons to move freely.
Applications in cutting-edge technology
Many modern technologies extensively use giant covalent structures:
- Graphene is revolutionising fields like electronics and nanotechnology.
- Silicon dioxide is a critical material in semiconductors. It is the backbone of the computer and smartphone industry.
Environmental and economic impact
There are sustainability and cost-effective benefits to using giant covalent structures:
- Solar cells that use graphene are more efficient and environmentally friendly.
- Silicon dioxide is inexpensive because it is found in abundance. It is a practical choice for many industries.
Conclusion - Giant Covalent Structures revision
Giant covalent molecules have unique physical properties, such as high melting points, exceptional strength and diverse applications. They help us understand natural phenomena and technological advancements. From the hardness of diamonds to the importance of graphene in nanotechnology, these substances show how important chemistry is in shaping our world.
For further reading, there are plenty of visual examples of the unique properties of these substances. For example, this is a video of someone trying to break a diamond with a hammer. You can also try the questions on giant covalent molecules by Quizizz to test your knowledge.
If you need personalised help tackling this topic, consider booking a lesson with TeachTutti's GCSE Chemistry tutors. Our tutors are qualified and have an enhanced DBS check. Lessons can be online or in-person to suit your needs.
This post was updated on 30 Nov, -0001.
