Molecular Compounds

Question 1

Why are the melting and boiling points of covalent compounds low?

Answer 1

Because it doesn’t take much energy to overcome the weak intermolecular forces

Question 2

Why is up it that covalent compounds are not able to conduct electricity?

Answer 2

In covalent bonds electrons are shared between 2 atoms, the forces between the positive and negative charged nuclei are held in place so electrons can’t flow or carry a current

Question 3

How does the the length of polymer molecules affect their melting and boiling points?

Answer 3

Longer polymers have higher boiling points than shorter ones

Question 4

What are the 4 allotropes of carbon?

Answer 4

Diamond, graphite, graphine and fullerenes

Question 5

What are the properties of fullerenes? Why are they like this?

Answer 5

Has a low melting point, molecules themselves are strong. It has a low melting point because of weak intermolecular forces

Question 6

What are the properties of graphite? Why are they like this?

Answer 6

Has strong bonds within the molecules, but weak forces between them and has a high melting and boiling point to melt the solid

Question 7

What are the properties of diamond? Why is it like this?

Answer 7

It’s got a giant covalent structure, it’s poor conductor because electrons aren’t free to move its got a very high melting and boiling point because there needs to be a lot of energy to over come the strong forces of attraction

Question 8

What are the properties of graphine? Why is it like this?

Answer 8

2D structure with strong covalent bonds. Is a good conductor because electrons are free to move

Question 9

Describe the bonding in metals?

Answer 9

Metallic bonding is the force of attraction between the positive metal ions and the negative delocalised electrons high melting and boiling point

Question 10

Explain why metals have a high melting point and boiling point?

Answer 10

The forces of attraction is strong

Question 11

Explain why metals are malleable?

Answer 11

The ‘sea’ of electrons holds the ions together so it changes shape instead of breaking

Question 12

Explain why metals conduct electricity?

Answer 12

When a potential difference (voltage) is applied between two points on a piece of metal, the electrons will flow towards the positive side. This flow transfers energy and forms an electrical current

Question 13

Which factor increases the electrical conductivity of metals?

Answer 13

Electrical conductivity increases when the number of delocalised electrons increase

Question 14

What is the structure and properties of ionic bonds?

Answer 14

Structure - billions of ions held together in a lattice structure
Properties - high melting and boiling point, many are soluble in water, conducts electricity when liquid or in a solution but doesn’t in a solid

Question 15

What is the structure and properties of simple molecular (covalent) bonds?

Answer 15

Structure - small, distinct groups of atoms

Properties - low melting and boiling point, a few are soluble in water, most do not conduct electricity

Question 16

What is the structure and properties of giant covalent bonds?

Answer 16

Structure - billions of atoms held together in a lattice structure
Properties - high melting and boiling points, insoluble in water, most do not conduct electricity (except in carbon as graphite)

Question 17

What is the structure and properties of metallic bonding?

Answer 17

Structure - billions of ions held together in a giant lattice structure of positive ions in a ‘sea’ of negative delocalised electrons
Properties - high melting and boiling points, insoluble in water, conducts electricity when solid or liquid

Question 18

What are the advantages of using the different models to show bonding?

Answer 18

So you can represent information in different ways

Question 19

How does the strength in covalent bonds compare to the intermolecular forces?

Answer 19

Covalent bonds have strong electrostatic forces of attraction but intermolecular forces are weak