chemical changes

Question 1

What happens in oxidation reactions?

Answer 1

A substance often gains oxygen and it loses electrons.

Question 2

What happens in reduction reactions?

Answer 2

A substance often loses oxygen and gains electrons.

Question 3

How are metal oxides formed?

Answer 3

Metals react with oxygen to form metal oxides.

Question 4

What happens when a metal reacts?

Answer 4

Their atoms lose electrons to form positive metal ions. The more easily an electron is lost the more reactive it is.

Question 5

What is the reactivity series?

Answer 5

The reaction of metals with acid and water can be used to place them in order of reactivity. This is called the reactivity series.

Question 6

When metals react with acids what is produced?

Answer 6

Metal salts and hydrogen.

Question 7

What happens in a displacement reaction?

Answer 7

A more reactive metal will displace a less reactive metal from a solution of its salt.
Eg magnesium + copper sulfate = copper + magnesium sulfate.

Question 8

What are metals more reactive than carbon extracted by?

Answer 8

Extracted from molten compounds in electrolysis.

Question 9

OILRIG

Answer 9

Oxygen is the loss of electrons.
Reduction is the gain of electrons.

Question 10

What happens to substances dissolved in water?

Answer 10

They dissociate into their individual ions.

Question 11

Acid + metal hydroxide =?

Answer 11

Salt + Water

Question 12

What do acids and alkalis contain?

Answer 12

Acids contain hydrogen ions H+ (aq)
Alkalis contain hydroxide ions OH- (aq)

Question 13

H+ (aq) + OH- (aq) =?

Answer 13

H20(l)

Question 14

acid + metal oxide =?
Acid + metal carbonate=?

Answer 14

salt + water
salt+ water + carbon dioxide

Question 15

What salts do hydrochloric, nitric and sulfuric acid produce?

Answer 15

Hydrochloric acid produces chloride salts.
Nitric acid produces nitrate salts.
Sulfuric acid produces sulfuric salts.

Question 16

(RP) Preparation of a pure, dry sample of soluble salt from an insoluble oxide or carbonate.

Answer 16

1) Add the metal oxide or carbonate to a warm solution of acid until no more will react.
2) Filter the excess metal oxide or carbonate to leave a solution of the salt.
3) Gently warm the salt solution so that the water evaporates and crystals of salt are formed.

Question 17

What happens to weak and strong acids in water?

Answer 17

Strong acids are completely ionised (split up into ions) in water.
Weak acids are only partially ionised in water.

Question 18

What is electrolysis?

Answer 18

It is the use of an electrical current to break down compounds containing ions into their elements.

Question 19

What are electrodes and electrolytes?

Answer 19

Electrodes are made from solids and conduct electricity.
Electrolytes is the substance being broken down.

Question 20

What happens during electrolysis?

Answer 20

-Negatively charged ions move the anode (positive electrode
-Positively charged ions move to the cathode (negative electrode).

Question 21

What does cryolite do?

Answer 21

It lowers the melting point of aluminium oxide meaning less energy is needed making it cheaper.

Question 22

When is hydrogen produced?

Answer 22

It is produced at the cathode if the metal is more reactive than hydrogen. (Potassium Sodium lithium Calcium
Magnesium Aluminium Zinc Iron.

Question 23

Where will the halogen be produced if the aqueous solution contains halide ions?

Answer 23

At the anode.