C4 Chemical Changes

Question 1

What is oxidation/ reduction?

Answer 1

Oxidation- when a substance gains oxygen
Reduction- when a substance loses oxygen

Question 2

What are metal oxides?

Answer 2

Metals react with oxygen to produce metal oxides. The reactions are oxidation reactions because the metals gain oxygen.

Question 3

What is the reactivity series?

Answer 3

When metals react with other substances the metal atoms form positive ions. The reactivity of a metal is related to its tendency to form positive ions. Metals can be arranged in order of their reactivity in a reactivity series. The metals potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids.

Question 4

What happens when acids react with metals?

Answer 4

Acids react with some metals to produce salts and hydrogen.

Question 5

What is the general equation for acids reacting with metals?

Answer 5

Metal + acid→salt + hydrogen

Question 6

What is the method for extracting three metal oxides?

Answer 6

1. Place 1 spatula of copper oxide into a crucible
2. Add a spatula of charcoal to the same crucible and mix
3. Heat the crucible, gently at first and then more strongly
4. After heating strongly for 3 minutes, empty the contents of your tube onto a heat proof mat.
5. Observe any changes you see (look for any metal that may have formed). 6. Repeat the process with the other metal oxides.

Question 7

What happens in electrolysis of aqueous solutions?

Answer 7

The ions discharged when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the elements involved.
• At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen.
• At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced.
• This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged.

Question 8

What charge is the anode?

Answer 8

Positive

Question 9

What charge is the cathode?

Answer 9

Negative

Question 10

What happens in electrolysis of molten ionic compounds?

Answer 10

When a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes, the metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the anode.