Chapter 5 - Chemical Changes

Question 1

metal + oxygen –>

Answer 1

metal oxide

Question 2

Metal + water —>

Answer 2

metal hydroxide + hydrogen

Question 3

Metal + acid —>

Answer 3

salt + hydrogen

Question 4

How does potassium, sodium and lithium react with oxygen?

Answer 4

they react with oxygen very vigourously at room temperature

Question 5

How does calcium, magnesium, zinc, iron, copper and silver react with oxygen?

Answer 5

react very slowly when heated

Question 6

How does gold react with oxygen?

Answer 6

does not react

Question 7

How does sodium, lithium and calcium react with water?

Answer 7

they react with water

Question 8

How does potassium react with water?

Answer 8

it burns with a lilac flame

Question 9

How does copper, silver and gold react with water?

Answer 9

do not react

Question 10

How does potassium, sodium and lithium react with acid?

Answer 10

they have an extremely violent reaction

Question 11

How does calcium, magnesium, zinc and iron react with acid?

Answer 11

reacts to form salts and hydrogen gas

Question 12

How does copper, silver and gold react with acid?

Answer 12

do not react

Question 13

what is the order of the reactivity series

Answer 13

Question 14

what are displacement reactions?

Answer 14

a more reactive metal can displace a less reactive metal from a compound

Question 15

define oxidation

Answer 15

when a substance loses electrons

Question 16

define reduction

Answer 16

when a substance gains electrons

Question 17

what is a redox reaction

Answer 17

a reaction in which both oxidation and reduction has occurred.

Question 18

how are high and medium reactivity metals found?

Answer 18

they are found as ‘ores’

Question 19

how are low reactivity metals found?

Answer 19

found naturally
‘pure’ or ‘native’

Question 20

How are elements that are more reactive than carbon extracted?

Answer 20

through electrolysis

Question 21

How are elements that are less reactive than carbon extracted?

Answer 21

through reduction by carbon

Question 22

give an example of reduction by carbon?

Answer 22

copper oxide + carbon –> copper + carbon dioxide

carbon has gained oxygen, while copper has lost oxygen

this is a redox reaction

Question 23

metal + acid –>

Answer 23

salt + hydrogen

Question 24

metal oxide + acid –>

Answer 24

salt + water

Question 25

metal hydroxide + acid -->

Answer 25

salt + water

Question 26

alkali + acid -->

Answer 26

salt + water

Question 27

what is an alkali?

Answer 27

a base that can dissolve in H2O

Question 28

metal carbonate + acid -->

Answer 28

salt + water + carbon dioxide

Question 29

chloride ion

Answer 29

Cl-

Question 30

sulphate ion

Answer 30

SO42-

Question 31

Nitrate ion

Answer 31

NO3-

Question 32

Describe how you can make copper sulfate crystals

Answer 32

1. Add excess copper oxide into a beaker with sulfuric acid (this is to ensure all of the acid is reacted) 2. Once reacted, filter the solution to get rid of the excess copper oxide 3. Heat solution to allow the water to evaporate 4. Copper sulfate crystals will start to form 5. Turn off the heat and let the rest of the water evaporate

Question 33

define acid

Answer 33

an acid dissolves in water to produce H+ ions (hydrogen)

Question 34

give an example of acid dissolving in water.

Answer 34

HCl ---> H+ + Cl- the acid dissociated to form a hydrogen ion and leaves behind a negative ion from the acid

Question 35

define alkali

Answer 35

an alkali dissolves in water to produce hydroxide ions (OH-)

Question 36

give an example of alkali dissolving in water.

Answer 36

NaOH --> Na+ + OH- the alkali dissociated to form a negative hydroxide ion and a positive metal ion from the

Question 37

what is the pH scale?

Answer 37

a measure of how acidic or alkaline a substance is

Question 38

which colours are: most acidic most alkaline neutral

Answer 38

red: strong acid yellow: weak acid green: neutral blue: weak alkali purple: strong alkali

Question 39

give a way to measure pH

Answer 39

universal indicator

Question 40

what happens in neutralisation reactions?

Answer 40

in neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water. H+ + OH- ---> H2O

Question 41

give an example of a neutralisation reaction

Answer 41

HCl + NaOH ---> NaCl + H2O

Question 42

define strong acids

Answer 42

they fully dissociate into ions when they dissolve in water there are no molecules of the original acid left, and the change is not reversible

Question 43

define weak acids

Answer 43

they do not fully dissociate into ions when they dissolve in water only some of the original acid molecules dissociate into ions and the change is reversible

Question 44

give 2 examples of strong and weak acids

Answer 44

strong: hydrochloric acid nitric acid weak: ethanoic acid citric acid

Question 45

how is the pH of acids related to the concentration of H+ ions

Answer 45

the more H+ ions in the solution, the lower the pH