1.2 How bonding and structure are related to the properties of substances

Question 1

Properties of ionic compounds

Answer 1

• High MP and BP (large amount of energy needed to break the many strong bonds).
• Conduct electricity when molten or aqueous (strong electrostatic forces need to be overcome so electrons are free to move and charge can flow)
• Strong electrostatic force of attraction acting in all directions between oppositely charged ions.

Question 2

Why are alloys harder than pure metals?

Answer 2

1. Alloys are mixtures of other metals.
2. Atoms are different sizes.
3. Regular layers are distorted.
4. Cannot slide.
5. This makes the alloy harder.

Question 3

Types of small covalent structures

Answer 3

• Hydrogen (single bond)
• Halogens (single bond)
• Water (single bonds)
• Ammonia (single bonds)
• Oxygen (double bond)
• Nitrogen (triple bond)
• Hydrochloric acid (single bonds)
• Methane (single bonds)

Question 4

Properties of small covalent molecules

Answer 4

• Usually gases or liquids.
• Low MP and BP (the larger the molecules, the larger the intermolecular forces so the higher the MP and BP).
• Weak intermolecular forces between molecules.
• Cannot conduct electricity (no delocalised electrons and molecules do not have overall electric charge).

Question 5

Properties of polymers

Answer 5

• Very long chain of repeating units called monomers.
• Strong covalent bonds between atoms in polymer molecules.
• Weak but many intermolecular forces between monomers (more energy needed to break forces).
• Solid at room temperature.

Question 6

Properties of giant covalent structures

Answer 6

• Solids
• High MP.
• Strong covalent bonds between all atoms.

Question 7

Types of covalent structures

Answer 7

• Diamond (form of carbon)
• Graphite (form of carbon)
• Silicon dioxide (silica)