bonding, structure and the properties of matter

Question 1

What causes chemical bonds to exist?

Answer 1

Electrostatic forces of attraction causes chemical bonds to exist.

Question 2

Describe the process of ionic bonding.

Answer 2

ionic bonding:

1) the electron(s) in the outer shell of the metal are transferred to the outer shell of the non-metal
2) the metal is a + ion and the non-metal is a - ion
3) there is now strong electrostatic forces of attraction between the ions
4) an ionic bond is formed.

Question 3

Describe the process of covalent bonding.

Answer 3

covalent bonding:
the positive nuclei are attracted to the shared pair of electrons by electrostatic forces of attraction, so there is a covalent bond. there are small (water), large (polymers) and giant (diamond and silicone dioxide) covalent bonds.

Question 4

Describe metallic bonding and how this proves why metals are excellent conductors, have high melting points and why they are malleable

Answer 4

Metals consist of giant structures of atoms in a regular pattern. Electrons in the outer shell of the metal atoms are delocalised, so they are free to move across the structure. Now, the metals are + ions. There are strong electrostatic forces of attraction between the - electrons and the + ions. This metallic bond explains the high melting and boiling points, and why they are excellent conductors of heat and electricity. The layers of atoms can slide over each other, so they are malleable.

Question 5

What are ionic compounds? What is their melting point and can they conduct electricity?

Answer 5

Ionic compounds are a giant structure of ions of a lattice held together by electrostatic forces of attraction. They have high melting and boiling points because the strong electrostatic forces that require a great deal of energy to break. They cannot conduct electricity as a solid as the ions are held in place and cannot flow. They can when they are an aqueous or liquid.

Question 6

What is the melting point and conduction of small covalent molecules like and why?

Answer 6

small covalent bonds:

• low melting and boiling points, so most are a gas at room temperature. this is due to strong electrostatic forces of attraction within the molecules, but weak intermolecular forces, so not a lot of energy required to break it
• as the size of the covalent molecule increases, the intermolecular forces increase
• don’t conduct electricity as the molecules don’t have an overall charge

Question 7

Describe the structure of polymers and how they are written.

Answer 7

polymers:

• these are very large covalent molecules
• they are made by joining together thousands of smaller, identical molecules (monomers)
• these intermolecular forces are relatively strong, so it’s solid at room temperature
• the monomers are all strong covalent bonds
• polymers are written as the monomer in brackets and the number outside (n) is how many monomers are in it

Question 8

Are giant covalent structures solid at room temperature, do they have a high or low melting point and do they conduct electricity? Why?

Answer 8

Giant covalent structures are always solid at room temperature due to the millions of strong covalent bonds. Therefore, they have high melting and boiling points. They don’t conduct electricity as they don’t contain charged particles.

Question 9

Describe the structure of diamond.

Answer 9

diamond:

• allotrope of carbon, giant covalent structure
• each carbon atom forms four covalent bonds
• very rigid structure

Question 10

Describe the structure of silicon dioxide.

Answer 10

silicon dioxide:

• silicon and oxygen covalently bonded
• giant covalent structure

Question 11

Describe the structure of graphite.

Answer 11

graphite:

• allotrope of carbon, giant covalent structure
• each carbon atom forms three covalent bonds in a hexagonal shape
• rings are in layers, so no bonds between layers so they can slide, so it is soft and slippery
• each carbon atom has one electron not used in a bond, so this is a delocalised electron that can move and conduct. therefore, conductor of heat and electricity

Question 12

Describe the structure of graphene.

Answer 12

graphene:

• a single layer of graphite (one carbon atom with three other carbon atoms), so one atom thick
• delocalised electron in each bond makes it a great conductor of electricity and heat
• extremely strong due to strong bonds, but won’t add weight so good for materials

Question 13

What are fullerenes?

Answer 13

fullerenes:

• molecules of carbon atoms with hollow shapes
• usually hexagonal rings, but can be five or seven

Question 14

What are the uses of fullerenes?

Answer 14

uses of fullerenes:

• pharmaceutical delivery into the body
• lubricants
• catalysts due to huge surface area, so catalyst molecules can be attached

Question 15

Describe the structure of buckminsterfullerene.

Answer 15

buckminsterfullerene:

• first fullerene to be discovered
• hollow sphere with 20 hexagons and 12 pentagons
• 60 carbon atoms

Question 16

Describe the structure of carbon nanotubes.

Answer 16

carbon nanotubes:

• hexagonal rings in a long cylinder
• high tensile strength (won’t break)
• can conduct due to delocalised electrons
• good for nanotechnology

Question 17

Describe how alloys are harder than pure metals.

Answer 17

Some metals aren’t hard enough to be useful. An alloy is a mixture of metals. The different size of atoms distorts the layers of atoms, making it more difficult for them to slide over each other.

Question 18

What are the positives and limitations in the dot and cross diagram?

Answer 18

dot and cross:

• very clear where electrons are coming from
• don’t show the shape of the molecule

Question 19

What are the limitations in the 2D stick diagram?

Answer 19

2D stick:

• can’t tell which electron came from which atom
• don’t know about electrons not in bond
• don’t know shape

Question 20

What are the positives and limitations in the 3D stick diagram?

Answer 20

3D stick:

• shows shape
• doesn’t show electrons not in bonds

Question 21

What are the positives and limitations in the ball and stick diagram?

Answer 21

ball and stick:

• clearly see ions in 3D
• ions shown are wide spread when really they are packed together

Question 22

What are the positives and limitations in the space filling diagram?

Answer 22

space filling:

• see how close the ions are
• can’t see 3D well

Question 23

Describe a solid.

Answer 23

A solid is extremely hard to compress as the particles are packed together with no spaces. It is a fixed shape and the particles only vibrate in fixed positions.

Question 24

Describe a liquid.

Answer 24

A liquid is hard to compress as the particles are close together. They flow to fill the container as the particles can flow over each other.

Question 25

Describe a gas.

Answer 25

A gas is easy to compress as the particles are wide spread. The particles fill the container as the particles move randomly.

Question 26

What are the limitations of the simple particle model of matter?

Answer 26

particle model:

• assumes the particles are solid spheres, but really have lots of different shapes and aren’t solid
• assumes that there are no forces between the particles

Question 27

What is the diameter range of coarse particles?

Answer 27

Coarse particles have a diameter between 2,500-10,000nm.

Question 28

What is the diameter range of fine particles?

Answer 28

Fine particles have a diameter between 100-2,500nm.

Question 29

What is the diameter range of nanoparticles?

Answer 29

Nanoparticles have a diameter between 1-100nm. They only contain a few hundred atoms.

Question 30

Why are nanoparticles used as catalysts?

Answer 30

Nanoparticles are used as catalysts as they have a huge surface area to volume ratio, so there is much less nanoparticles needed for the same surface area.

Question 31

What are the uses of nanoparticles?

Answer 31

uses of nanoparticles:

• catalysts
• medicine as can be absorbed into the body
• some can conduct electricity
• cosmetics and clothes as silver nanoparticles have anti-bacterial properties

Question 32

What is the risk of nanoparticles?

Answer 32

risk of nanoparticles:

- can enter cells, but no one knows the effects of this