Bonding, structure and properties of matter

Question 1

Why is hydrogen chloride a gas at room temperature?

Answer 1

Small/simple molecular (covalent) structure. Has weak intermolecular forces that require little energy to overcome.

Question 2

Why would you not expect titanium chloride to be a liquid at room temperature?

Answer 2

Metal chlorides are usually ionic in a giant ionic lattice regular structure so have high melting points as they have strong electrostatic forces between oppositely charged ions in all directions which require a lot of energy to overcome and break.

Question 3

Explain why sodium oxide has a high melting point.

Answer 3

It is an ionic compound so has a giant (ionic lattice) structure with strong electrostatic forces between oppositely charged ions in all directions which require large amounts of energy to overcome and break the forces.

Question 4

Describe the structure and bonding of sulfur dioxide

Answer 4

• Has covalent bonds as between two non-metals
• In a giant (covalent) structure

Question 5

What is the name for alloys that can return to their original shape when heat is applied to them?

Answer 5

Shape memory alloys.

Question 6

Explain why graphite is a good conductor.

Answer 6

Giant structure with three covalent bonds per carbon atom so one electron is delocalised per carbon atom. These electrons can move through the structure and carry a charge.

Question 7

Explain why graphite is soft and slippery.

Answer 7

Giant structure arranged in layers of hexagonal rings with weak intermolecular forces between the layers so layers can easily slide over each other.

Question 8

Explain why a buckminsterfullerene is a good lubricant.

Answer 8

Spherical so molecules will roll (over each other).

Question 9

Explain why nanoparticles are cheaper to use.

Answer 9

High surface area to volume ratio so smaller quantities can be used for the same effect

Question 10

Suggest 2 reasons why alloys are used rather than pure gold for jewellery. (24k=100%)

Answer 10

1. cheaper
2. harder

Question 11

Compare properties of copper and graphite.

Answer 11

• Copper has strong metallic bonds in a giant (metallic) structure and has layers that can slip over each other so malleable
• Copper is a good conductor of electricity
• Graphite is also a good conductor but has hexagonal layers in a giant covalent structure that can slip over each other, making graphite more brittle and weak than copper

Question 12

Explain how corrosion affects conductivity of a metal when exposed to air.

Answer 12

The metal reacts with oxygen during corrosion to become a solid ionic compound. This decreases conductivity as ions are fixed in place in a solid giant ionic lattice structure so they can’t move and can’t carry a charge through the structure.

Question 13

Explain why liquid iodine does not conduct electricity.

Answer 13

Simple/small molecular structure. Have no free electrons or ions to carry charge through structure so no overall charge.

Question 14

Explain how metals conduct electricity.

Answer 14

Giant lattice structure with a sea of delocalised electrons. Therefore, (delocalised) electrons can move and carry a charge through the structure.

Question 15

Give one reason why fullerenes are good for drug delivery.

Answer 15

Hollow shaped molecules so they can trap the drug.

Question 16

Explain why a mixture of oxygen and methane does not react at room temperature in terms of particles.

Answer 16

Particles need to collide with sufficient energy to react. Room temperature means particles don’t have sufficient energy to react and therefore won’t collide successfully.

Question 17

Why are thermosetting polymers better than thermosoftening polymers for cooking equipment?

Answer 17

Won’t melt when heated as they have bonds/cross links between polymer chains

Question 18

How do you know an ionic compound is present?

Answer 18

A metal + a non metal that ends usually in -ide

Question 19

What are limitations of the particle model?

Answer 19

• No forces shown
• Atoms are shown as solid spheres

Question 20

What is a limitation of dot and cross diagrams?

Answer 20

It does not show its 3D shape

Question 21

Why do metals have strong metallic bonds?

Answer 21

The sharing of negative delocalised electrons which are strongly attracted to the positive metal ions

Question 22

When can ionic compounds conduct electricity and why?

Answer 22

When molten or dissolved in water(aqueous), ionic compounds conduct electricity because the ions are free to move and so charge can flow

Question 23

Why are metals good conductors of thermal energy?

Answer 23

Energy is transferred by the delocalised electrons through the structure

Question 24

Explain why methane and poly(ethene) exist in different states at rtp

Answer 24

Methane is a small/simple covalent molecule structure so has weaker intermolecular forces which require less energy to overcome whereas poly(ethene) is a large covalent molecule structure. This means methane has a lower melting and boiling point than methane.

Question 25

Suggest why alloys do not conduct electricity as well as pure metals

Answer 25

Alloys are a mixture of atoms with different sizes which distort the layers. This means movement of electrons is restricted so can’t carry charge through structure as easily.

Question 26

Suggest two reasons why nanoparticles are used instead of fine particles

Answer 26

• Larger surface area to volume ratio
• Less can be used for same effect

Question 27

Explain the properties of nanotubes

Answer 27

• High length to diameter ratio plus high tensile strength which is good for strengthening composites (like tennis rackets)
• Conduct electricity due to delocalised electrons (it is a fullerene which is just graphene folded)

Question 28

Explain how a covalent bond holds two atoms together

Answer 28

Strong forces of attraction between negative electrons and both positively charged nuclei

Question 29

Explain why alloys are harder than pure metals

Answer 29

Mixture of metals so atoms have different sizes. This distorts layers. Layers slide over each other less easily.