Chemical changes

Question 1

How do metals react with air (oxygen)

Answer 1

Metal + oxygen —> metal oxide

Question 2

What is oxidation?

Answer 2

Oxidation is the loss of electrons, gain of oxygen.

Question 3

What is reduction?

Answer 3

Reduction is the gain of electrons, loss of oxygen.

Question 4

What is the arrangement of metals in reactivity series?

Answer 4

Pottasium
Sodium 
Calcium
Magnesium
Aluminium
CARBON
Zinc 
Iron
HYDROGEN
Copper
Silver
Gold

Question 5

What are displacement reactions?

Answer 5

A more reactive element can displace a less reactive element out of its compound during a chemical reaction.

Question 6

How do metals and dilute acids react?

Answer 6

metal + acid –> salt + hydrogen

salt = (metal plus acid)

Question 7

How do metals and water react?

Answer 7

metal + water –> metal hydroxide + hydrogen

Question 8

Relate the reactivity series to its tendency to form positive ions.

Answer 8

When metals react with other substances, the metal atoms lose electrons to form positive ions. (They lose an electron to gain a full outer shell).

Question 9

What are native metals?

Answer 9

Native metals are unreactive metals that are found in the Earth as the metal itself (no chemical reactions are needed to separate it as it is not part of a compound).

Question 10

How can carbon be used to extract metals?

Answer 10

If a metal is less reactive than carbon, it can be extracted from its oxide by heating with carbon.
The carbon displaces the metal from the compound, and removes the oxygen from the oxide.
This leaves the metal.

Question 11

What happens with the ions in ionic displacement reaction equations?

Answer 11

Ions have to be the same on both sides. The less reactive metal loses the ions and gives it to the more reactive metal.

Question 12

What are redox reactions?

Answer 12

Where both reduction and oxidation takes place.

Question 13

What is neutralisation?

Answer 13

Neutralisation is the reaction of an acid with a base that results in the pH moving towards 7.

Question 14

What is a base?

Answer 14

A base is a substance that can neutralize the acid by reacting with hydrogen ions.

Question 15

What are two examples of bases?

Answer 15

Metal oxides and alkalis.

Question 16

What happens when you mix an acid and alkali?

Answer 16

Acid + alkali –> salt + water

Neutralises acid

Question 17

What happens when you mix an acid and metal oxide?

Answer 17

Acid + metal oxide –> salt + water

Neutralises acid

Question 18

What happens when an acid mixes with a metal carbonate?

Answer 18

Acid + metal carbonate —> salt + water + carbon dioxide

Neutralises acid

Question 19

How can soluble salt be made from acids?

Answer 19

Acid + insoluble reactant –> soluble salt

Question 20

What is the pH scale?

Answer 20

1 ———> 7 ———> 13

acid neutral alkali

Question 21

What is an acid in relation to hydrogen ions (H+)?

Answer 21

An acid is a substance that produces hydrogen ions, H+, when dissolved in water.

Question 22

What is an alkali in relation to hydroxide ions (OH-)?

Answer 22

An alkali is a substance that produces hydroxide ions, OH-, when dissolved in water.

Question 23

How does universal indicator work (pH scale)?

Answer 23

If universal indicator is added to a solution it changes to a colour that shows the pH of the solution.

Question 24

What are the terms concentration and dilute referring to (acids)?

Answer 24

A concentrated acid is one in which many acid molecules are dissolved in a set volume of solution, while a dilute acid will have very few molecules per unit volume.
CONCENTRATED = LOTS OF ACID MOLECULES
DILUTE = FEW ACID MOLECULES

Question 25

What are the terms weak and strong referring to (acids)?

Answer 25

``` Weak = only slightly ionises in an aqueous solution Strong = completely ionised in an aqueous solution. ```

Question 26

Why do ionic compounds conduct electricity when dissolved in water or liquid?

Answer 26

Ionic compounds conduct electricity when liquid or in aqueous solution, because their ions are free to move from place to place. Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move.

Question 27

What are electrolytes?

Answer 27

A substance that breaks up into ions (particles with electrical charges) when it is dissolved in water. It can conduct electricity as its ions are free to move, allowing charge to flow.

Question 28

What are ions?

Answer 28

Particles that have electrical charge.

Question 29

What is electrolysis?

Answer 29

Electrolysis is the process by which ionic substances are broken down into simpler substances. An electric current is passed through them.

Question 30

Describe the process of electrolysis (molten ionic compounds).

Answer 30

Positively charged ions move to the negative electrode (CATHODE). They receive electrons and are reduced. Negatively charged ions move to the positive electrode (ANODE). They lose electrons and are oxidised. OPPOSITES ATTRACT!

Question 31

How do you predict what will form at either the anode or cathode during electrolysis?

Answer 31

The METAL is formed at the CATHODE because that is where the positive metal ions are attracted. The NON-METAL is formed at the ANODE where the negative non-metal ions are attracted. OPPOSITES ATTRACT!

Question 32

Why are some metals extracted using electrolysis and not carbon?

Answer 32

Because the metals are more reactive than carbon.

Question 33

How do you extract metals using electrolysis?

Answer 33

EXAMPLE - aluminium Aluminium oxide and want to make it just aluminium. Positively charged aluminium ions gain electrons from the cathode, and form molten aluminium. Oxide ions lose electrons at the anode, and form oxygen molecules.

Question 34

What are metal ions?

Answer 34

They are positively charged so are attracted the the negative electrode (CATHODE).

Question 35

Describe electrolysis of ionic compounds.

Answer 35

CATHODE: The METAL is produced at the cathode if it is LESS RECATIVE than HYDROGEN. HYDROGEN is produced at the cathode if the METAL if the metal is LESS REACTIVE. ANODE: OXYGEN is produced, unless HALIDE IONS (chloride, bromide or iodide ions) are present. In that case, the negatively charged halide ions lose electrons and form the corresponding halogen (CHLORINE, bromine or iodine).

Question 36

Which out of oxidation and reduction happens at the anode and cathode?

Answer 36

The reaction at the anode is oxidation. | The reaction at the cathode is reduction.