Properties of solids

Question 1

Metals conduct electricity because…

Answer 1

They have delocalised electrons which are free to move

Question 2

Graphite conducts electricity because…

Answer 2

Each C atom is only bonded to 3 other C atoms, so there is one delocalised electron per C which is free to move

Question 3

Ionic solids do not conduct electricity because…

Answer 3

The ions are arranged in a rigid lattice and cannot move

Question 4

Ionic solids conduct electricity when molten or aqueous because…

Answer 4

The lattice structure is broken and the ions are free to move

Question 5

Diamond does not conduct electricity because…

Answer 5

Each C atom is bonded to 4 other C atoms and there are no delocalised electrons

Question 6

Molecular covalent substances do not conduct electricity because…

Answer 6

they have no delocalised electrons or charged ions

Question 7

Metals are insoluble in water because…

Answer 7

There is no attraction of the polar water molecules for the metal atoms in the lattice so the metallic bond is not broken

Question 8

Diamond is not soluble in water because…

Answer 8

There is no attraction of the polar water molecules for the carbon atoms in the lattice so the covalent bond is not broken

Question 9

Graphite is not soluble in water because…

Answer 9

There is no attraction of the polar water molecules for the carbon atoms in the lattice so the covalent bond is not broken

Question 10

Ionic substances are soluble in water because…

Answer 10

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

Question 11

Non-Polar covalent molecules are insoluble in water because…

Answer 11

There is no attraction between the polar water molecules and the non-polar molecules so the attractive forces are not broken

Question 12

Polar covalent molecules are soluble in water because…

Answer 12

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

Question 13

Non-Polar covalent molecules are soluble in non-polar solvents (eg cyclohexane) because…

Answer 13

The attraction between the molecules and the solvent is similar, allowing them to mix

Question 14

Polar covalent molecules are insoluble in non-polar solvents (eg cyclohexane) because…

Answer 14

There is no attraction between the delta + and delta - of the molecule and the non-polar solvent, so they will not mix

Question 15

Covalent Networks (diamond and SiO₂) are hard because…

Answer 15

The strong covalent bonds hold atoms in a rigid 3D lattice and require a large amount of force to deform this structure

Question 16

Graphite is soft and slippery because…

Answer 16

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

Question 17

Metals and malleable and ductile because…

Answer 17

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

Question 18

Ionic solids are brittle because…

Answer 18

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

Question 19

Molecular covalent substances are soft because…

Answer 19

The weak intermolecular forces holding the molecules together require a small amount of energy to break. The molecules themselves are not broken