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Chemistry GCSE AQA > Topic 4 Chemical Changes > Flashcards

Topic 4 Chemical Changes Flashcards

Key Terms/Key Knowledge

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1
Q

What is electrolysis?

A

The splitting up of an ionic compound using electricity. The electric current is passed through a substance causing chemical reactions at the electrodes and the decomposition of the materials.

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2
Q

What is an electrolyte?

A

A solution containing free ions from the molten or dissolved ionic substance. The ions are free to move to carry charge.

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3
Q

What is the positive electrode?

A

Anode

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4
Q

What is the negative electrode?

A

Cathode

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5
Q

What happens at the cathode? (Higher Only)

A

It is where positively charged ions gain electrons and so the reactions are reductions.

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6
Q

What happens at the anode? (Higher Only)

A

It is where negatively charged ions
lose electrons and so the reactions are oxidations.

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7
Q

In aqueous solutions what is produced at the negative electrode (cathode)?

A

Hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen.
A solid coat layer of the pure metal will form on the cathode if less reactive than hydrogen.

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8
Q

In aqueous solutions what is produced at the positive electrode (anode)?

A

Oxygen is produced from the discharged hydroxide ions unless the solution contains halide ions then the halogen is produced.

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9
Q

What happens to the ions during electrolysis?

A

Positively charged ions move to the negative electrode (cathode), and negatively charged ions move to the positive electrode (anode).

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10
Q

Where are metals formed? Why?

A

Cathode because metals are positive ions.

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11
Q

Where are non-metals formed? Why?

A

Anode because non-metals are negative ions.

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12
Q

What is OILRIG?

A

Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)

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13
Q

In electrolysis of lead bromide (molten ionic compound) what is produced where?

A

The metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the anode.

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14
Q

Why is extracting metals from electrolysis expensive?

A

Because large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current.

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15
Q

Why can solid substances not be electrolysed?

A

They do not conduct electricty, or the ions cannot move.

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16
Q

Why is aluminium oxide mixed with cryolite?

A

Because aluminium oxide has a very high melting point and cryolite can lower it so it is easier to melt.

17
Q

What metals are extracted by electrolysis?

A

Metals more reactive than carbon.
Metals that have reacted with carbon also.

18
Q

In electrolysis of aluminium oxide why do the anodes have to be replaced?

A

Because oxygen is formed, which reacts with the carbon of the positive electrodes, forming carbon dioxide, and they gradually burn away .

19
Q

What are the anodes in electrolysis of aluminium oxide made of ?

A

Graphite

20
Q

What is an acid?

A

Acids produce hydrogen ions (H+) in aqueous solutions. They have a pH range of 0-6.

21
Q

What is an alkali?

A

Alkalis produce hydroxide ions (OH-) in aqueous solutions. They have a pH range of
8-14.

21
Q

What is Displacement ?

A

A chemical reaction in which a more reactive element displaces a less reactive element from its compound.

22
Q

What is Extraction?

A

Extraction techniques are used to separate a desired substance when it is mixed with others.

23
Q

What is Neutralisation?

A

Neutralisation

24
Q

What is Oxidation? (Higher Only)

A

A reaction involving the gain of oxygen. Oxidation is the loss of electrons.

25
Q

What is pH scale?

A

The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe.

26
Q

What is *Redox reaction?

A

A reaction in which both oxidation and reduction occur simultaneously.

27
Q

What is Reduction? (Higher Only)

A

A reaction involving the loss of oxygen. Reduction is the gain of electrons.

28
Q

What is Strong acid? (Higher Only)

A

A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.

29
Q

What is Weak Acid? (Higher Only)

A

A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.

30
Q

What is Universal Indicator?

A

A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.

31
Q

What is The reactivity series?

A

Metals are arranged in order of their reactivity in a reactivity series. This can be used to predict products from reactions.

32
Q

What is *Titration?

A

A technique used where a solution of known concentration is used to determine the concentration of an unknown solution.

Chemistry GCSE AQA (11 decks)

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