C2 Bonding, structure and the properties of matter

Question 1

Describe fullerenes and give a named example.

Answer 1

Fullerenes are molecules of carbon atoms with hollow shapes.

The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.

The first fullerene to be discovered was buckminsterfullerene (C60) which has a spherical shape.

Question 2

Describe the bonding in diamond and some of its properties.

Answer 2

In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.

Question 3

Polymers have very strong covalent bonds between atoms, true or false?

Answer 3

TRUE! Atoms in polymers are held in palce by strong covalent bonds.

Question 4

Describe what a monomer looks like.

Answer 4

A monomer is an unsaturated compound with a double bond.

Question 5

Explain why polymer molecules are solids at room temperature.

Answer 5

Polymer molecules are solid at room temperature because they have relatively strong intermolecular forces between polymer chains.

Question 6

Describe the structure of graphene and give one use of this material.

Answer 6

Graphene is made up of a single layer of graphite. It can be used in electrical circuits.

Question 7

What are carbon nanotubes and why are they useful?

Answer 7

Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.

Question 8

Describe the bonding in graphite.

Answer 8

In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.

In graphite, one electron from each carbon atom is delocalised.

Question 9

What are the three states of matter?

Answer 9

The three states of matter are solid, liquid and gas.

Question 10

List the state symbols used in chemical equations.

Answer 10

• Solid (s)
• Liquid (l)
• Gas (g)
• Aqueous (aq)

Aqueous means the substance is dissolved in water.

Question 11

Describe some of the physical properties of small molecules.

Answer 11

Small molecules are usually gases or liquids that have relatively low melting points and boiling points.

Question 12

What determines the melting and boiling point of substances?

Answer 12

The melting and boiling points of substances are determined by the forces between the particles.

This depends upon the structure and bonding within the substance.

Question 13

What is the pattern in melting and boiling points as molecule size gets bigger?

Answer 13

The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.

Question 14

Do metals lose or gain electrons?

Answer 14

Metals lose electrons.

Question 15

Do non metals lose or gain electrons?

Answer 15

Non metals gain electrons.

Question 16

What is the charge of a metal ion?

Answer 16

The charge of a metal ion is positive.

Question 17

What is the charge of a non-metal ion?

Answer 17

The charge of a non-metal ion is negative.

Question 18

What is an ionic bond?

Answer 18

An ionic bond is the strong electrostatic force of attraction between oppositely charged ions

Question 19

What are the three types of chemical bonds?

Answer 19

The three types of chemical bonds are ionic bonds, covalent bonds and metallic bonds.

Question 20

Describe the the strength of the intermolecular forces between small molecules.

Answer 20

Small molecules have only weak forces between the molecules (intermolecular forces).

It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.

Question 21

Where do ionic bonds form?

Answer 21

Ionic bonds form between metals and non-metals.

Question 22

Where do covalent bonds form?

Answer 22

Covalent bonds form between non-metal atoms.

Question 23

What is an ionic compound and how are ions held together?

Answer 23

An ionic compound is a giant lattice structure.

Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions.

Question 24

What is a giant ionic lattice?

Answer 24

A giant ionic lattice is made up of oppositely charged ions held together by electrostatic forces acting in all directions. This is called ionic bonding.

Question 25

What does the picture of the giant ionic lattice of sodium chloride look like?

Answer 25

Question 26

Draw a dot and cross diagram showing the formation of NaCl. Include electronic configurations.

Answer 26

Question 27

Why do ionic compunds conduct electricity when molten or dissolved, but not when solid?

Answer 27

When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow | (because dissolving ionic compounds breaks up lattice structure)

Question 28

Why do ionic compounds have high melting points?

Answer 28

Ionic bonding produces ions which are held together by strong electrostatic forces of attraction (ionic bonds) Ions are held in a giant lattice structure There are many strong bonds to break Large amounts of energy needed to overcome these strong bonds.

Question 29

Ionic bonding involves the transfer of what?

Answer 29

Ionic Bonding involves the transfer of electrons.

Question 30

What is a covalent bond?

Answer 30

A covalent bond is the strong electrostatic atraction between the positive nuclei and the shared paris of electrons

Question 31

Do small covalent molecules conduct electricity?

Answer 31

No, small covalent molecules do not conduct electricity as there is no overall charge or spare ions or electrons to carry a charge.

Question 32

Giant covalent structures are solids with high melting points. Expalin why.

Answer 32

Giant covalent compounds are solids with high metling points because the atoms are held together by strong covalent bonds that require large amounts of energy to break them.

Question 33

Describe the properties of graphite in relation to its structure.

Answer 33

Graphite is soft and slippery becuase of the weak intermolecular forces between layers. The delocalised electrons allow graphite to carry an electrical charge so it conducts electricity.

Question 34

Give three examples of giant covalent structures.

Answer 34

Three examples of giant covalent structures are diamond, graphite and silicon dioxide.

Question 35

What is metallic bonding?

Answer 35

Strong electrostatic forces of attraction between the positive ions surrounded by a sea of delocalised electrons

Question 36

Why do metals conduct electricity.

Answer 36

Metals conduct electricity because delocalised electrons are free to carry the electrical charge.

Question 37

Pure metals can be bent or drawn into wires. What are the names given to these properties?

Answer 37

Metals that can be bent are called malleable. Metals that can be drawn into wires are called ductile.

Question 38

How are pure metals made harder?

Answer 38

Pure metals are made harder by combining them with other metals to make alloys.

Question 39

What are simple molecular structures?

Answer 39

Composed of small molecules that contain relatively few atoms with weak intemrolecular forces betwene the molecules

Question 40

What are giant covalent structures?

Answer 40

Made from a huge number of atoms all covalently bonded together

Question 41

What are the properties of simple covalent molecules?

Answer 41

* Low melting and boiling points * Do not conduct electricity * Intermolecular forces get stronger with the size of the atom

Question 42

Why do simple covalent molecules not conduct electricity even when they are molten or dissolved?

Answer 42

They do not contain any free ions or electrons that can carry the charge

Question 43

What is an allotrope?

Answer 43

Pure forms of the same element but have different structures

Question 44

(Q) Explain what the formula 'MgO' means (3)

Answer 44

One magnesium atom reacts with one oxygen atom and electrons are transferred. A magnesium atom loses 2 electrons to form a Mg 2+ ion. The oxygen atom gains 2 electrons to form an O 2- ion. These oppositely charged ions are held together by strong ionic bonds.

Question 45

(Q) What are the advantages and disadvantages of the 2D ball and stick model?

Answer 45

Advantages: - Shows the atoms bonded to each other Disadvantages: - Does not show the shape of the molecule

Question 46

(Q) Suggest why alloys do not conduct electricity as well as pure metals (2)

Answer 46

Alloys have an irregular arrangement and contains different types of atoms that are of different sizes which disrupts the layers. This means that delocalised electrons cannot move through the alloy as freely to carry charge as they can in a pure metal.

Question 47

(Q) Metals have stong metallic bonding which makes them have high melting and boiling points. Explain why.

Answer 47

Strong metallic bonds are held together by strong forces of attraction between positive metal cations and delocalised electrons. They need lots of energy to be broken.

Question 48

(Q) What are the advantages and disadvantages of the 3D ball and stick model?

Answer 48

Advantages: - Shows the shape of the molecule Disadvantages: - Does not show it is bonded via electrons - (FOR Qs) Not a true representation of the structure of compounds since there are no gaps or sticks between the ions in reality.

Question 49

(Q) What are the advantages and disadvantages of the dot and cross diagram?

Answer 49

Advantages: - Shows electrons for each atom Disadvantage: - It is a 2D representation

Question 50

(Q) Explain why chlorine is a gas at room temperature, but sodium chloride is a solid at room temperature

Answer 50

Chlorine is a gas because: - it is a simple molecular structure - forces between the molecules are weak - so they have low melting / boiling points - because less energy is needed to overcome the weak forces Sodium chloride is a solid because - has ionic bonds (strong electrostatic forces of attraction) between oppositely charged ions in all directions - forming a giant lattice structure - so high melting / boiling points - because lots of energy is needed to break the bonds

Question 51

(Q) Explain why CO2 has a very low boiling point

Answer 51

Carbon dioxide is a simple molecular structure. There are weak intermolecular forces of attraction between the molecules therefore little energy is needed to overcome these forces.

Question 52

(Q) Explain why nanotubes are strong

Answer 52

Strong covalent bonds between carbon atoms

Question 53

(Q) Would you expect sodium chloride or potassium chloride to have a higher melting point?

Answer 53

Sodium chloride because - ions have the same charge so there is the same electrostatic forces between particles - soidum ions are smaller however, so the forces have a larger effect

Question 54

(Q) Describe what happens when two atoms of potassium react with one atom of sulfur

Answer 54

- 2 electrons are transferred from 2 potassium atoms to 1 sulfur atom. - Each potassium atom loses 1 electrons to form a completed outer shell which forms a positive K + ion. - The sulfur atom gains 2 electrons to form a completed outershell to form a negative S 2- ion. - These oppositely charged ions are held together by strong electrostatic forces of attraction. - The solid ionic compound formed is potassium sulfide (K2S)