Properties of solids Flashcards
Link physical properties to the structure of solids
Metals conduct electricity because…
They have delocalised electrons which are free to move
Graphite conducts electricity because…
Each C atom is only bonded to 3 other C atoms, so there is one delocalised electron per C which is free to move
Ionic solids do not conduct electricity because…
The ions are arranged in a rigid lattice and cannot move
Ionic solids conduct electricity when molten or aqueous because…
The lattice structure is broken and the ions are free to move
Diamond does not conduct electricity because…
Each C atom is bonded to 4 other C atoms and there are no delocalised electrons
Molecular covalent substances do not conduct electricity because…
they have no delocalised electrons or charged ions
Metals are insoluble in water because…
There is no attraction of the polar water molecules for the metal atoms in the lattice so the metallic bond is not broken
Diamond is not soluble in water because…
There is no attraction of the polar water molecules for the carbon atoms in the lattice so the covalent bond is not broken
Graphite is not soluble in water because…
There is no attraction of the polar water molecules for the carbon atoms in the lattice so the covalent bond is not broken
Ionic substances are soluble in water because…
The delta + H of the polar water attracts the - ion, and the delta - O of the water attracts the + ion. The ionic bond is broken and the solid dissolves
Non-Polar covalent molecules are insoluble in water because…
There is no attraction between the polar water molecules and the non-polar molecules so the attractive forces are not broken
Polar covalent molecules are soluble in water because…
The delta + H of the polar water attracts the delta - end of the molecule, and the delta - O of the water attracts the delta + end of the molecule. The attractive forces are similar, which allows them to mix
Non-Polar covalent molecules are soluble in non-polar solvents (eg cyclohexane) because…
The attraction between the molecules and the solvent is similar, allowing them to mix
Polar covalent molecules are insoluble in non-polar solvents (eg cyclohexane) because…
There is no attraction between the delta + and delta - of the molecule and the non-polar solvent, so they will not mix
Covalent Networks (diamond and SiO2) are hard because…
The strong covalent bonds hold atoms in a rigid 3D lattice and require a large amount of force to deform this structure
Graphite is soft and slippery because…
The 2D layers of covalently bonded carbon atoms are held together by weak intermolecular forces, which require a low amount of energy to break and can slide over each other
Metals and malleable and ductile because…
The metallic bonds holding the atoms in the lattice are non-directional. When a force is applied the layers of atoms move without creating any repulsive forces, so the metal deforms but does not break
Ionic solids are brittle because…
The ionic bonds are directional between alternating + and - ions. When a force is applied the layers move and like charges line up and repel, which causes the ionic bonds to break
Molecular covalent substances are soft because…
The weak intermolecular forces holding the molecules together require a small amount of energy to break. The molecules themselves are not broken
