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C3: Structure and Bonding (States of Matter (Solids-Have a fixed shape and…
C3: Structure and Bonding
States of Matter
Solids
-Have a fixed shape and volume and cannot be compressed. Particles vibrate
Liquids
-Have a fixed volume but can flow a change their shape. Particles slip and slide over each over.
Gases
-Have no fixed or volume and can be compressed. Particles move quickly and erratically. as the particles bash against the walls of the container they exert a force that causes pressure
Changes of state are reversible and no new substances are formed
The hotter a solid is the faster it vibrates. Eventually, the vibrations are so strong it breaks away from its neighbours and forms a liquid
As the temperature of a liquid rises, the particles escape from the surface of the liquid. Eventually, it boils and gas bubbles rise and escape.
The temperature of the substance stops rising at a certain point when being heated because the energy is being used to break the bonds and change state
When cooling a substance the temperature stops decreasing because energy is transferred to the surroundings as stronger forces form between particles
The simple particle model has limitations because the atoms, molecules and ions that makeup substances are not solid spheres with no forces between them
Atoms Into Ions
Covalent bonding
-Sharing electrons
Ionic bonding
-Transferring electrons (losing or gaining) to form ions.
Non-metals gain electrons to form negative ions
Metals lose electrons to form positive ions
Ionic Bonding
Ions formed are held together are held together by very strong forces of attraction. Otherwise known as the electrostatic force of attraction
Ionic bonds between charged particles result in giant structures/giant lattices
Group 1 = 1+ ions, Group 2 = 2+ ions, Group 3 = 3+ ions, Group 4 = most do not form ions, Group 5 = 3- ions, Group 6 = 2- ions, Group 7 = 1- ions, Group 0 = do not form ions
Giant Ionic Structures
The attractive electrostatic forces between the oppositely charged ions are very strong. This means the ions in the lattice are held very tightly
It takes large amounts of energy to break an ionic lattice because you must overcome the strong electrostatic forces
Ionic compounds can only conduct electricity when
molten or in solution otherwise there will be no delocalised electrons to carry the charge
Giant Covalent Structures
Diamond, silicon dioxide, and graphite have giant covalent structures
Giant covalent structures have high melting and boiling points, are insoluble in water, hard and do not conduct electricity (apart from graphite)
Bonding in Graphite
carbon atoms are bonded to three other carbon atoms to form hexagonal layers
The layers have weak intermolecular forces between them which means the layers can slide over each other quite easily
The carbon atoms in graphite's layers have one free electron (
delocalised electrons
) which can carry around the electric charge, allowing graphite to conduct electricity
Fullerenes and Graphene
They are made of carbon atoms and can be shaped as footballs, rugby balls, doughnuts, and more
Cylindrical fullerenes or carbon nanotubes have high tensile strength and high electrical and thermal conductivity
Fullerenes can be used to deliver drugs or radioactive atoms to treat cancer at specific sites in the body
They can also be used as lubricants or catalyst due to the large surface area to volume ration of the nanoparticles
Graphene is a single sheet of carbon atoms from graphite and is better at conduting thermal energy and electricity than graphite
Graphene is the most reactive form of carbon and has a very low density
Bonding In Metals
The atoms in metals are layered in a regular pattern meaning that they form crystals (although not always visible to the human eye)
Pure metals are another example of a giant structure. They form a lattice of positively charged ions.
Delocalised electrons
- A 'sea' of free moving electrons that are no longer linked with any particular metal ion. This allows the metal to conduct electricity and thermal energy
The strong electrostatic forces of attraction between the electrons and protons bond the metal ions to each other
Giant Metallic Structures
Pure metals can be hammered into different shapes because the layers of atoms can easily slide over each
Alloys are usually mixtures of metals so the atom sizes vary, making it difficult for the layers to slide over each other so they are harder
The delocalised electrons in the structure move around
and
hold the metal ions together. This means that the lattice can be distorted when hit
Metals have high melting points
-The electrostatic forces of attraction extend in all directions (due to free movement of electrons) so it takes a lot of energy to separate the metal ions.
Nanoscienece
1 nanometre (1nm) = 1×10−9 m
The particles in the air are known as particulate matter e.g. pollen or dust. Nanoparticles are invisible in light
Coarse particles are 10 micrometres wide, fine particles 0.1 - 2.5 micrometres wide
Nanoparticles have a high surface area to volume ratio which makes them incredibly reactive and can lead to a more sustainable industry because less resources are used
Nanoparticles have most of their atoms/molecules on the surface of the particle