C5 Flashcards
Identify the elements and compounds that dry air consists of?
Oxygen, nitrogen, argon and carbon dioxide
Identify the relative proportions of the main gases in the atmosphere?
78% Nitrogen, 21% Oxygen, 1% argon 0.04% carbon dioxide
Identify the symbols atoms and molecules of nitrogen; oxygen;argon; CO2
N2, O2, Ar, CO2
Describe the melting and boiling points of compounds have low melting and boiling points?
They have low melting and boiling points
Why do molecular element and compounds have low melting points?
Because they have weak inter-molecular forces that require little energy to overcome
Why do pure molecular compounds not conduct electricity?
Because their molecules are not charged
What type of bonding exists within molecules?
Covalent
Define covalent bonding
The electrostatic attraction between the nuclei of the atoms and the electrons shared between them.
Compare the strength of covalent bond within to the inter-molecular forces between small covalent molecules
Covalent bonds within molecules are strong compared with the weak inter-molecular forces between molecules.
What makes up the Earth’s hydrosphere?
Oceans, seas, lakes and rivers that consist mainly of water with some dissolved compounds, called salts
How are the ions in crystals of solid ionic compounds arranged?
The ions are arranged in a lattice structure
Define ionic bonding
The electrostatic attraction between oppositely charged ions
Describe and explain the melting points of solid ionic compounds
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
Describe what happens to the ions when an ionic crystal dissolves in water.
The regular crystal lattice breaks down into positive and negative ions that are free to move.
Why do ionic compounds conduct electricity when dissolved in water?
Because the ions are charged and they are to move around independently in the liquid
Why can the ions in a ionic compound be detected and identified?
Because they have distinct properties and they form compounds with distinct properites
What is the name given to an insoluble compound formed upon mixing of two solutions of ionic compounds?
A precipitate
Explain how some metal ions can be identified in solution.
By adding alkali they form insoluble hydroxide with characteristic colours
What is the Earth’s lithosphere?
It is the rigid outer layer of the earth , Made up of crust and encrusted with a mixture of minerals
What re minerals like diamond and graphite both made from?
Carbon atoms
Describe and explain the properties of diamond
-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
Describe and explain the properties of graphite
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
Name three elements that are very abundant in the earths crust
oxygen. silicon, aluminium
Much of the silicon and oxygen present in the earth’s crust is in the form of what?
The compound silicon dioxide
Describe the structure of silicon dioxide. What other substances does it have similar to diamond.
It is a giant covalent compound and has properties similar to diamond.
Describe the term ‘ore’
An ore is a rock that contains varying amounts of minerals from which metals metal can be extracted
In terms of the amounts of ore,needed what is one problem with copper mining?
A large amount of ore needs to be extracted in order to record small percentage of copper.
Which three metal can be extracted by heating their oxides with carbon
zinc, iron, copper
Describe the extraction of metals using carbon in terms of oxidation and reduction.
When a metal oxides loses oxygen it is reduced, while the carbon gains oxygen and is oxidised
Why can’t all metals be extracted using carbon.
Those that are more reactive than carbon cannot be extracted
Define the term electrolysis
The decomposition of an electrolyte with an electric current
Describe what happens to ion when an ionic crystal melts
The ions separate ad become free to move
During electrolysis, where to the metals and metals form at in terms of electrodes.
Metals form the negative electrode and non-metals form at the positive electrode.
Aluminium can be extracted by the electrolysis of aluminium oxide . Explain the process using ideas about ions and electron gain and loss.
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
Write an ionic equation to show the reaction at the negative electrode in the electrolysis of aluminium oxide.
AL3+ +3e+ = Al
