C5 - Chemical Changes

Question 1

What is the reactivity series?

Answer 1

A list of metals with the most reactive metals at the top and the least reactive at the bottom. The order is:
Potassium (Fizz in water, explode in acid)
Sodium
Lithium
Calcium
Magnesium (Slow react in water, fizz + salt in acid)
Aluminium
Zinc
Iron
Tin (Slight react in water, slow react in acid)
Lead
Copper
Silver
Gold (No react)

Question 2

What is a displacement reaction?

Answer 2

Where a metal on the reactivity series takes another metal’s place in a salt.

Question 3

What is oxidation?

Answer 3

The loss of electrons.

Question 4

What is reduction?

Answer 4

The gain of electrons.

Question 5

What is a metal ore?

Answer 5

A lump of rock which contains enough of a mineral to make it worth extracting and purifying. Some minerals are not found in ore form, e.g. gold.

Question 6

How are minerals extracted from ores?

Answer 6

If the mineral is below aluminium on the reactivity series, the mineral is displaced using carbon to obtain the raw mineral.

If the mineral is or is above aluminium on the reactivity series, electrolysis is used to extract the mineral.

Question 7

What is a salt?

Answer 7

A salt is a compound where the hydrogen in an acid has been partially replaced by metal ions.

Question 8

How are salts formed?

Answer 8

By reacting an acid with an element above Hydrogen in the reactivity series to produce a displacement reaction. This also produces hydrogen gas as a side product.

Question 9

What happens when you react an acid with a base (non-soluble alkali)?

Answer 9

acid + base -> a salt + water

The ions in the salt in this reaction add to a charge of zero.

Question 10

How do you make copper salt from copper oxide?

Answer 10

• Add copper oxide to sulfuric acid.
• Warm gently.
• The solution should turn blue. Filter into a beaker.
• Warm solution above boiling water until crystals begin to form.
• Leave for 2 days for crystals to form.

Question 11

What happens when you react an acid with a carbonate?

Answer 11

acid + carbonate -> a salt + water + carbon dioxide

Question 12

What is the pH scale?

Answer 12

A measure of how acidic or alkaline solution is. 0 is acidic, whilst 14 is alkaline. 7 is perfectly neutral.
As the pH decreases by one unit (becomes more acidic), the hydrogen ion concentration of the solution increases by a factor of 10.