Chemical Changes

Question 1

Reactivity series in order

Answer 1

potassium
sodium
lithium
calcium
magnesium
CARBON
zinc
iron
HYDROGEN
copper
silver
gold
platinum

Question 2

metals + acids =

Answer 2

metal salts + hydrogen

Question 3

alkalis + water =

Answer 3

metal hydroxide solution + hydrogen

Question 4

why is it not safe to react lithium, sodium and potassium with dilute acid?

Answer 4

because they would react so vigorously

Question 5

metal + oxygen =

Answer 5

metal oxide

Question 6

How does potassium react in cold water?

Answer 6

potassium reacts very quickly and the hydrogen produced ignites instantly and the metal sets alight, sparking and burning under a lilac flame

Question 7

How does sodium react in cold water?

Answer 7

fizzes rapidly and melts to form a ball that moves around on the water surface

Question 8

How does lithium react in cold water?

Answer 8

fizzes steadily and floats becoming smaller until it eventually disappears

Question 9

which metals do not react with dilute acids?

Answer 9

copper, gold, silver, platinum

Question 10

which metals react with dilute acid but not cold water?

Answer 10

magnesium, aluminium, zinc, iron and lead

iron and lead react really slowly

Question 11

How are metals extracted?

Answer 11

• most metals are found as metal oxides or compounds that can easily be changed to metal oxides
• Metals less reactive than carbon can be extracted from their oxides by reduction with carbon
• Metals that are more reactive than carbon are extracted from their molten compounds by electrolysis

Question 12

briefly explain oxidation and reduction in terms of electrons

Answer 12

oxidation is loss

reduction is gain

Question 13

What happens when substances dissolve in water?

Answer 13

dissociate into individual ions

Question 14

What do acids produce in aqueous solutions?

Answer 14

H + ions

Question 15

What do alkalis produce in aqueous solutions

Answer 15

OH- ions

Question 16

What can the pH of a solution be measured with?

Answer 16

universal indicator
litmus paper
pH probe

Question 17

what is a base?

Answer 17

a substance with a pH greater than 7

an alkali is A SOLUBLE base

Question 18

acid + base =
acid + metal hydoxide =

(these are the same result)

Answer 18

salt + water

this is neutralisation

Question 19

acid + metal oxides =

Answer 19

salt + water

Question 20

acids + metal carbonate =

Answer 20

salt + water + carbon dioxide

Question 21

metal carbonate, metal oxides, alkalis, metal hydroxides all neutralise acids. this makes them what?

Answer 21

bases

Question 22

How are soluble salts made?

Answer 22

by reacting acids with insoluble bases

Question 23

What examples of insoluble bases

Answer 23

metals, metal oxides, hydroxides or carbonates.

Question 24

What are strong acids?

Answer 24

acids that ionise completely in water

all particles dissociate to release H+ ions

Question 25

What are weak acids?

Answer 25

acids that do not fully ionise in a solution

only a small proportion of acids particles dissociate to release H+ ions

Question 26

What are examples of strong acids?

Answer 26

hydrochloric, nitric and sulfuric acids.

Question 27

What is the pH of a solution a measure of?

Answer 27

the concentration of H+

Question 28

What are examples of weak acids?

Answer 28

ethanoic, citric and carbonic acids.

Question 29

When the pH of a solution decreases by one unit, the hydrogen ion concentration does what?

Answer 29

increases by a factor of 10

Question 30

DONT MIX UP strong acids and concentrated solution

what is the difference between these two?

Answer 30

acid strength (strong or weak) tells you what proportion of the acid molecules ionise in water

concentration measures how much acid there is in a certain volume of water

Question 31

what salt does hydrochloric acid produce?
Nitric acid
sulfuric acid

Answer 31

chlorides
nitrates
sulfates