GCSE Chemistry: Chemical Changes Flashcards

Question 1

Define Reactivity Series.

Accepted Answer

A list of metals arranged in order of how readily they react, based on how easily their atoms lose electrons to form positive ions.

Question 2

Define Displacement Reaction.

Accepted Answer

A reaction in which a more reactive element takes the place of a less reactive element in a compound, pushing the less reactive one out.

Question 3

Define Oxidation (Oxygen Definition).

Accepted Answer

A reaction in which a substance gains oxygen. Metals reacting with oxygen to form metal oxides are the classic examples.

Question 4

Define Reduction (Oxygen Definition).

Accepted Answer

A reaction in which a substance loses oxygen. Extracting a metal from its oxide ore is a reduction of that oxide.

Question 5

Define Oxidation (Electron Definition).

Accepted Answer

The loss of electrons by an atom or ion, which makes its charge more positive. This is the Higher tier definition of oxidation.

Question 6

Define Reduction (Electron Definition).

Accepted Answer

The gain of electrons by an atom or ion, which makes its charge more negative. This is the Higher tier definition of reduction.

Question 7

Define Redox Reaction.

Accepted Answer

A reaction in which oxidation and reduction happen at the same time, because the electrons lost by one substance are gained by another.

Question 8

What is Ore?

Accepted Answer

A rock that contains enough of a metal or metal compound to make extracting the metal economically worthwhile.

Question 9

Define Native Metal.

Accepted Answer

A metal so unreactive that it is found in the Earth's crust as the uncombined element rather than in a compound.

Question 10

Define Extraction by Reduction with Carbon.

Accepted Answer

A method of obtaining metals that are less reactive than carbon by heating their oxides with carbon, which removes the oxygen.

Question 11

Define Ionic Equation.

Accepted Answer

An equation showing only the particles that actually change in a reaction, leaving out the ions that stay the same throughout.

Question 12

Define Spectator Ion.

Accepted Answer

An ion that is present in the reaction mixture but is unchanged at the end, so it is left out of the ionic equation.

Question 13

Define Half Equation.

Accepted Answer

An equation showing what happens to one species during a redox reaction or at one electrode, with electrons written in to balance the charge.

Question 14

What is Acid?

Accepted Answer

A substance that produces hydrogen ions, H+, when dissolved in water. Aqueous acid solutions have a pH below 7.

Question 15

What is Base?

Accepted Answer

A substance that reacts with an acid to neutralise it, forming a salt and water. Metal oxides and metal hydroxides are bases.

Question 16

What is Alkali?

Accepted Answer

A base that dissolves in water, producing hydroxide ions, OH−, in solution. Alkaline solutions have a pH above 7.

Question 17

What is Neutralisation?

Accepted Answer

The reaction between an acid and a base that produces a salt and water, in which hydrogen ions react with hydroxide ions.

Question 18

What is Salt?

Accepted Answer

An ionic compound formed when the hydrogen in an acid is replaced by a metal or ammonium ion.

Question 19

Define pH Scale.

Accepted Answer

A scale from 0 to 14 measuring how acidic or alkaline a solution is. Below 7 is acidic, 7 is neutral and above 7 is alkaline.

Question 20

Define Universal Indicator.

Accepted Answer

A mixture of dyes that changes through a range of colours to show the approximate pH of a solution.

Question 21

Define Strong Acid.

Accepted Answer

An acid that is completely ionised in aqueous solution, so every molecule releases its hydrogen ions into the water.

Question 22

Define Weak Acid.

Accepted Answer

An acid that is only partially ionised in aqueous solution, so most of its molecules keep their hydrogen and few ions are released.

Question 23

Define Concentrated vs Strong.

Accepted Answer

Concentration is the amount of acid dissolved in a given volume of solution, while strength is how fully that acid ionises. The two are independent.

Question 24

What is Titration?

Accepted Answer

A technique for finding the exact volumes of an acid and an alkali that react completely, by adding one from a burette until an indicator changes colour.

Question 25

What is Crystallisation?

Accepted Answer

A separation method that obtains a solid salt from its solution by evaporating some of the solvent and leaving the rest to cool so crystals form.

Question 26

What is Electrolysis?

Accepted Answer

The breaking down of an ionic compound, molten or in solution, into elements by passing an electric current through it.

Question 27

What is Electrolyte?

Accepted Answer

A molten or dissolved ionic compound that conducts electricity because its ions are free to move to the electrodes.

Question 28

What is Cathode?

Accepted Answer

The negative electrode in electrolysis, where positive ions are attracted and gain electrons, so reduction takes place there.

Question 29

What is Anode?

Accepted Answer

The positive electrode in electrolysis, where negative ions are attracted and lose electrons, so oxidation takes place there.

Question 30

Define Inert Electrode.

Accepted Answer

An electrode made of a material, usually graphite or platinum, that conducts electricity but does not take part in the reactions during electrolysis.

Question 31

What is Cryolite?

Accepted Answer

An aluminium compound used as a solvent for aluminium oxide in electrolysis, so the cell can run at a lower temperature and use less energy.