C5

Question 1

Identify the elements and compounds that dry air consists of?

Answer 1

Oxygen, nitrogen, argon and carbon dioxide

Question 2

Identify the relative proportions of the main gases in the atmosphere?

Answer 2

78% Nitrogen, 21% Oxygen, 1% argon 0.04% carbon dioxide

Question 3

Identify the symbols atoms and molecules of nitrogen; oxygen;argon; CO2

Answer 3

N2, O2, Ar, CO2

Question 4

Describe the melting and boiling points of compounds have low melting and boiling points?

Answer 4

They have low melting and boiling points

Question 5

Why do molecular element and compounds have low melting points?

Answer 5

Because they have weak inter-molecular forces that require little energy to overcome

Question 6

Why do pure molecular compounds not conduct electricity?

Answer 6

Because their molecules are not charged

Question 7

What type of bonding exists within molecules?

Answer 7

Covalent

Question 8

Define covalent bonding

Answer 8

The electrostatic attraction between the nuclei of the atoms and the electrons shared between them.

Question 9

Compare the strength of covalent bond within to the inter-molecular forces between small covalent molecules

Answer 9

Covalent bonds within molecules are strong compared with the weak inter-molecular forces between molecules.

Question 10

What makes up the Earth’s hydrosphere?

Answer 10

Oceans, seas, lakes and rivers that consist mainly of water with some dissolved compounds, called salts

Question 11

How are the ions in crystals of solid ionic compounds arranged?

Answer 11

The ions are arranged in a lattice structure

Question 12

Define ionic bonding

Answer 12

The electrostatic attraction between oppositely charged ions

Question 13

Describe and explain the melting points of solid ionic compounds

Answer 13

Because of the strong electrostatic forces between them, its takes a great deal of energy to separate the positive and negative ions in a crystal lattice.This means that ionic compounds have high melting points and boiling points

Question 14

Describe what happens to the ions when an ionic crystal dissolves in water.

Answer 14

The regular crystal lattice breaks down into positive and negative ions that are free to move.

Question 15

Why do ionic compounds conduct electricity when dissolved in water?

Answer 15

Because the ions are charged and they are to move around independently in the liquid

Question 16

Why can the ions in a ionic compound be detected and identified?

Answer 16

Because they have distinct properties and they form compounds with distinct properites

Question 17

What is the name given to an insoluble compound formed upon mixing of two solutions of ionic compounds?

Answer 17

A precipitate

Question 18

Explain how some metal ions can be identified in solution.

Answer 18

By adding alkali they form insoluble hydroxide with characteristic colours

Question 19

What is the Earth’s lithosphere?

Answer 19

It is the rigid outer layer of the earth , Made up of crust and encrusted with a mixture of minerals

Question 20

What re minerals like diamond and graphite both made from?

Answer 20

Carbon atoms

Question 21

Describe and explain the properties of diamond

Answer 21

-Diamond is a giant covalent structure
-It is made of carbon atoms , with each joined to four other by strong bonds.
Diamond is the hardest naturally occurring substance and has high melting points and boiling points( due to strong covalent bonds)
-Diamond has low electrical conductivity

Question 22

Describe and explain the properties of graphite

Answer 22

Graphite is another giant covalent structure made of carbon atoms.

• each carbon atom is joined to three others, forming layers; The bonds between the layers are much weaker than covalent bonds . This enables the layers to slide across each other ,making graphite soft.
• Graphite can also conduct electricity , because of the delocalised ( free) electrons between the layers of a crbon atoms

Question 23

Name three elements that are very abundant in the earths crust

Answer 23

oxygen. silicon, aluminium

Question 24

Much of the silicon and oxygen present in the earth’s crust is in the form of what?

Answer 24

The compound silicon dioxide

Question 25

Describe the structure of silicon dioxide. What other substances does it have similar to diamond.

Answer 25

It is a giant covalent compound and has properties similar to diamond.

Question 26

Describe the term ‘ore’

Answer 26

An ore is a rock that contains varying amounts of minerals from which metals metal can be extracted

Question 27

In terms of the amounts of ore,needed what is one problem with copper mining?

Answer 27

A large amount of ore needs to be extracted in order to record small percentage of copper.

Question 28

Which three metal can be extracted by heating their oxides with carbon

Answer 28

zinc, iron, copper

Question 29

Describe the extraction of metals using carbon in terms of oxidation and reduction.

Answer 29

When a metal oxides loses oxygen it is reduced, while the carbon gains oxygen and is oxidised

Question 30

Why can’t all metals be extracted using carbon.

Answer 30

Those that are more reactive than carbon cannot be extracted

Question 31

Define the term electrolysis

Answer 31

The decomposition of an electrolyte with an electric current

Question 32

Describe what happens to ion when an ionic crystal melts

Answer 32

The ions separate ad become free to move

Question 33

During electrolysis, where to the metals and metals form at in terms of electrodes.

Answer 33

Metals form the negative electrode and non-metals form at the positive electrode.

Question 34

Aluminium can be extracted by the electrolysis of aluminium oxide . Explain the process using ideas about ions and electron gain and loss.

Answer 34

During electrolysis of molten aluminium oxide, positively charged aluminium ions gain electrons from the negatively charged electrode to become neutral atoms which then combine to form oxygen molecules

Question 35

Write an ionic equation to show the reaction at the negative electrode in the electrolysis of aluminium oxide.

Answer 35

AL3+ +3e+ = Al