Topic 4 - Chemical Changes Flashcards
Describe how metals react with oxygen
What types of reactions are they and why?
Metals react with oxygen to produce metal oxides.
The reactions are oxidation reactions because the metals gain
oxygen.
When metals react with oxygen to form metal oxides and an oxidation reaction takes place
what is an ore
A compound from which a metal can be extracted for profit
iron + oxygen —->
iron + oxygen —> iron oxide
iron + oxygen —> iron oxide
in this reaction which element has been oxidised
what type of reaction is this
The iron has been oxidised because the iron has gained oxygen
This is an oxidation reaction because iron is gaining oxygen.
metal + oxygen —> metal oxide
in this reaction which element has been oxidised
the metal atoms have been oxidised
What is an oxidation reaction
Gaining oxygen is called a oxidation reaction
A reaction where oxygen is added to a substance or when electrons are lost from a substance
What is a reduction reaction
A reaction where oxygen is removed from a substance or electrons are gained
magnensium oxide —> magneisum + oxygen
what type of reaction is this and why?
what has happened
This is a reduction reaction become oxygen is being lost (removed) from the substance (magnesium oxide)
Here the magnesium atoms have been reduced
calcium + copper oxide –> calcium oxide + copper
which element has been oxidised and which element has been reduced
The calcium has been oxidised because it has gained oxygen (it has gone from calcium to calcium oxide)
The copper has been reduced because it has lost oxygen (it has gone from copper oxide to oxide)
metal + water–>
metal + water —> metal hydroxide + hydrogen
metal hydroxides are alkali’s
State the reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
Tin
Lead
(Hydrogen)
Copper
Silver
Gold
Platinum
What happens when metals react
When metals react, they lose electrons and form positive ions
show potassium forming the potassium ion
K —> K+ + e-
What does the reactivity of a metal depend on
What is the reactivity series based on
The reactivity of a metal depends on its tendency (ability/how easily they) to lose electrons and form a positive ion.
K —> K+ + e-
It shows potassium forming the potassium ion, K+ and losing one electron
In terms of a metals tendency to form a positive ion, what does it show to us regarding the reactivity series
More reactive metals readily ( will more easily/have a higher tendency) to lose electrons and form a positive ion while less reactive metals are much less likely (will less easily/lower tendency) to form a positive ion
potassium reaction with water
produces the alkali, potassium hydroxide and the gas, hydrogen
extremely vigorous reaction (lilac flame can be seen)
sodium reaction with water
produces the alkali, sodium hydroxide and the gas, hydrogen
reacts less rapidly with water than potassium
lithium reaction with water
produces the alkali, lithium hydroxide and the gas, hydrogen
reacts more slowly than potassium or sodium
reaction with water for potassium, sodium, lithium, (at room temperature) calcium
fizz, giving off hydrogen gas, leaving an alkaline solution of metal hydroxide
reacts very rapidly with water at room temp.
calcium - reacts quite rapidly with water at room temp.
reaction with water for magnesium, aluminium, zinc, iron
very slow reaction
(or no reaction with water at room temp.)
reaction with water for tin and lead
slight reaction with steam
reaction with water for copper, silver and gold
no reaction, even with steam
How to work out reactivity of metals
By testing a range of different metals with water, we can work out the reactivity of the metals
Using the metals reactivity with water, which metals can you determine their reactivity.
Why is this only a few?
The metal’s reaction with water can be used to determine the reactivity of potassium, sodium, lithium and calcium.
We cannot use water to determine the reactivity of mg,zn,Fe and Cu as they do not react with water
How to compare the reactivity of mg, zn, Fe, cu
To compare the reactivity of these metals, then react them with dilute acid
reaction with dilute acid for K, Na, Li, Ca
Explode
Dangerously fast reaction with acids
Calcium - Extremely vigorous reaction
reaction with dilute acid for mg, al, zn, Fe
Fizz giving off hydrogen gas and forming a salt
mg - rapid reaction
zn - quite rapid reaction
fe - quite slow reaction
reaction with dilute acid for lead and tin
react slowly with warm acid
reaction with dilute acid for copper silver gold
No reaction
Explain why aluminium can be used outdoors, for example for window frames, patio doors, even though it is quite high in the reactivity series
Aluminium is protected by a tough / impervious layer of aluminium
oxide
Aluminium reacts with the oxygen in the air to form an aluminium oxide layer.
Therefore it will not undergo reactions unless the oxide layer is removed.
This is why it can be used in window frames without corroding
For a displacement reaction, harry used different starting temperatures
Explain why this did not affect his results
Because the change in temperature is not affected by the initial temperature
Why was the highest rise in the temperature obtained with magnesium and copper sulphate (and not the acid reaction with zinc or iron)
Because mg and cu have the biggest different in reactivity compared to the different in reactivity with zn and cu, or fe and cu
Describe how certain metals can be extracted using carbon
Because carbon is more reactive than certain elements.
It is able to displace those elements from their compounds, which as a result leaves that certain metal, extracted in its elemental form.
__________
Many metals have been oxidised by oxygen in the air to form their oxides
So to extract the metal from their oxides, the metal oxide must be reduced.
Because carbon is more reactive than certain elements.
It is able to displace those elements from their compounds, which as a result leaves that certain metal, extracted in its elemental form.
Explain why gold is found in the earth as the metal itself
Because Gold is extremely unreactive (it does not easily react with other elements)
what are most metals found as in the Earth
most metals are found as compounds
Since most metals are found as compounds, what is needed to be done to extract the metal
most metals are found as compounds that require
chemical reactions to extract the metal.
Displacement fact
A more reactive element will displace (push out/take the place of) a less reactive element from its compound
explain why this is a displacement reaction
mg + iron oxide -> magnesium oxide + iron
Magnesium is more reactive than iron so it has displaced iron from its iron oxide compound
magnesuim + sodium oxide —> magnesium oxide + sodium
Is this correct. why?
This is not correct. A displacement reaction cannot occur.
This is because magnesium is less reactive than sodium, therefore it cannot displace (reduce) sodium from the sodium oxide compound
mg + iron oxide -> magnesium oxide + iron
in terms of oxygen, which atoms have been oxidised and reduced
Magnesium atoms have been oxidised because the magnesium atoms have gained oxygen
The iron atoms have been reduced because the iron atoms have lost oxygen
What elements can reduce iron
Any element that is more reactive than iron can reduce iron.
Why do we use carbon to reduce elements such as: zinc and iron
Any element that is more reactive than iron can reduce iron.
However, most of these elements are very expensive so in practice, carbon is used since it is extremely cheap.
carbon + iron oxide —>
carbon + iron oxide —>carbon dioxide + iron
symbol equation for the reduction of iron oxide using carbon
Fe2O3 + 3C —> 2Fe + 3CO
