1.4) Chemical Changes

Question 1

What happens when metal reacts with oxygen ?

Answer 1

• When a metal reacts with oxygen it forms a metal oxide and an oxidation reaction has taken place.
• The metal atoms have been oxidised

Question 2

What is happening in this reaction ?
Magnesium + Oxygen ➡️ Magnesium Oxide

Answer 2

Magnesium has GAINED oxygen, and gaining oxygen is called an OXIDATION reaction.
(This means that Magnesium has been oxidised)

Question 3

What is happening in this reaction ?
Magnesium Oxide ➡️ Magnesium + Oxygen

Answer 3

• Losing oxygen is called a reduction reaction
• Here the Magnesium atoms have been reduced

Question 4

What is happening in this reaction ?
Calcium + Copper Oxide ➡️ Calcium Oxide + Copper

Answer 4

• Calcium has been oxidised
• Copper has been reduced

Question 5

What actually determines how rapidly a metal reacts ?

Answer 5

• When metals react, they lose electrons and form a positive ion.
  K ➡️ (K+) + (e-)
• The reactivity of a metal depends on its ability to lose electrons and form a positive ion.

Question 6

What does the Reactivity Series consist of ?

Answer 6

Question 7

What is the word equation for the reaction of potassium and magnesium carbonate, and why?

Answer 7

-Potassium is more reactive than magnesium, and will therefore displace it from magnesium carbonate:
Potassium + magnesium carbonate → potassium carbonate + magnesium

Question 8

Why is carbon used to extract metals?

Answer 8

• Reducing a metal with carbon will result in the extraction of the metal if the metal is lower in the reactivity series than carbon.
• Carbon is used because it is cheap and abundant.

Question 9

How is carbon used to extract metals?

Answer 9

• In the reduction, the metal oxide loses oxygen to form a pure metal.
• Reduction with carbon normally involves heating the metal oxide in the presence of the carbon, which is often used in the form of coal.

Question 10

What happens to a metal oxide in a reduction reaction with carbon?

Answer 10

In a reduction reaction with carbon, a metal oxide loses oxygen to form a pure metal.

Question 11

Which metals react with dilute acids but not cold water?

Answer 11

Magnesium
Aluminum
Zinc
Iron
Lead

Question 12

Selina is investigating the reactivity of different metals.
1.1) Selina reacts magnesium with copper sulphate. What products would you expect from this reaction?
1.2) She finds that when she reacts sodium with calcium carbonate a reaction happens, but when zinc is reacted with calcium carbonate, no reaction happens.
Why is this the case and what products would be produced in the reaction of sodium with calcium carbonate?

Answer 12

1.1) Magnesium sulphate
Copper metal
1.2) Displacement reactions occur when a more reactive metal reacts to displace a less reactive metal in a compound.

Sodium is more reactive than calcium so the sodium displaces the calcium.

Calcium metal and sodium carbonate would be produced.

Question 13

What would you expect to happen when copper is heated with aluminum nitrate?

Answer 13

• No reaction would happen.
• This is because copper is less reactive than aluminum.

Question 14

Reaction of Metals with Acids

Answer 14

When acids react with metals, hydrogen and a salt are always formed. The first part of the salt’s name comes from the metal involved. The second part of the name comes from the acid.

Question 15

Example Reaction of Metal and Acid

Answer 15

Magnesium + hydrochloric acid → magnesium chloride + hydrogen

Question 16

Example Reaction of Metal and Acid

Answer 16

Zinc + sulfuric acid → zinc sulfate + hydrogen

Question 17

Example Reaction of Metal and Acid

Answer 17

Iron + sulfuric acid → iron sulfate + hydrogen

Question 18

What is it meant by a weak acid?

Answer 18

• Produces H+ ions in aqueous solution
• but is only partially ionised