Chem 2.4

Question 1

Conductors

Answer 1

Conduct electricity in solid and liquid states but are not chemically changed during conduction

Question 2

Electrolytes

Answer 2

Conduct electricity only in molten or aqueous state, and decomposed by electricity during conduction

Question 3

Non - conductors

Answer 3

Do not conduct electricity in any states

Question 4

Giant metallic structure

Answer 4

1. Metallic bonds are strong electrostatic attraction between positive metal ions and delocalized electrons.
2. It is non - directional since positive metal ions and delocalized electrons are attracted together in all directions
3. The metal ions in metal exists as a 3D arrangement in a ‘sea’ of delocalized electrons
4. The ions are closely packed together, forming giant metallic structure

Question 5

Why does giant metallic structure have high m.p./ b.p.?

Answer 5

It is because the metallic bonds between the delocalized electrons and positive metal ions is strong. Thus, a lot of energy is needed to break the bonds between them.

Question 6

Why does giant metallic structure conduct heat

Answer 6

It is because when heat is supplied to one end of the metal, the delocalized electrons will gain energy and move and vibrate faster, colliding with the neighboring slow delocalized electrons. Thus, heat is transferred.

Question 7

Why does giant metallic structure conduct electricity

Answer 7

When battery is connected to the metal, the delocalized electrons will move towards the positive pole, leaving the metal, while the same number of delocalized electrons will move into the metal from the negative pole.

Question 8

Why does giant metallic structure have high densities

Answer 8

It is because the metal atoms are closely packed in a regular arrangement by strong metallic bonds

Question 9

Why are giant metallic structure ductile and malleable?

Answer 9

1. Metal ions are packed in layers
2. When force is applied, the layers of ions will slide over each other easily without breaking the metallic bonds
3. Since delocalized electrons are free to move and the non - directional metallic bonds will still hold the ions together even though the position of the ions are changed

Question 10

Giant ionic structure

Answer 10

1. When metals react with non - metals
2. The atoms of the metal donate electrons to form cations while the atoms of the non - metal accept electrons to form anions
3. The oppositely charged ions are held regularly and closely together by strong ionic bonds to form a crystal lattice, thus they have a giant ionic structure

Question 11

Why are giant ionic structures soluble in water

Answer 11

1. Strong attractions between ions and water molecules overcome ( as they are stronger than ) the ionic bonds between the oppositely charged ions and the Van der Waals’ forces between water molecules.
2. The ions are pulled away from the lattice.
3. Then water molecules surrounded the ions.
4. The ions are said to be hydrated.

Question 12

Why is giant ionic structure brittle

Answer 12

1. It is because oppositely charged ions are held by strong ionic bond
2. When force is applied, relative movement brings the ions of the same charge close to each other
3. Repulsion between ions of the same charge occurs, breaking the crystal lattice

Question 13

Why are simple molecular structures insoluble in water

Answer 13

It is because the attraction between molecules of the substances and water is not strong enough to overcome the Van der Waals’ forces between water molecules.

Question 14

Simple molecular structures that are soluble in water

Answer 14

Cl2, HCl, SO2, NH3, sugar

Question 15

Simple molecular structure that can conduct electricity after reaction with water

Answer 15

Cl2, HCl, SO2, NH3

Question 16

Molecular size -> m.p/ b.p.

Answer 16

1. It is a XXX structure
2. XXX has a larger/ smaller molecular size
3. The Van der Waals’ forces between XXX is stronger
4. More/ less energy is needed to break the bonds between XXX

Question 17

Allotropes

Answer 17

Allotropes are different forms of the same element with different structures

Question 18

Why is diamond so hard

Answer 18

It is because carbon atoms in diamond are held by strong covalent bonds to form a giant tetrahedral network which restricts the relative motion between the carbon atoms. Hence, diamond is the hardest natural substance.

Question 19

Why does graphite conduct electricity

Answer 19

It is because every carbon atom is bonded with three other carbon atoms in graphite. delocalized electrons exist within carbon layers. When a battery is connected to graphite, the delocalized electrons move in the direction of an electric field. Hence, graphite is an electrical conductor and it can be used as electrodes in batteries.