Paper 1: Section 3- Chemical changes

Question 1

What is the pH scale?

Answer 1

The measure of how acidic or alkaline a solution is.

Question 2

What is a base?

Answer 2

A substance that reacts with an acid to produce salt and water.

Question 3

What are bases that are soluble in water called?

Answer 3

Alkalis

Question 4

The higher the concentration of ________ ions in a solution, the more acidic it is, so the _____ its pH will be.

Answer 4

1. hydrogen
2. lower

Question 5

In alkaline solutions the _______ the concentration of ________ ions and the _____ its pH will be.

Answer 5

1. higher
2. hydroxide
3. higher

Question 6

Name the 3 main indicators:

Answer 6

1. litmus
2. methyl orange
3. phenolphthalein

Question 7

What colour is litmus in acidic, neutral and alkaline solutions?

Answer 7

Acidic: red
Neutral: purple
Alkaline: blue

Question 8

What colour is methyl orange in acidic, neutral and alkaline solutions?

Answer 8

Acidic: red
Neutral: yellow
Alkaline: yellow

Question 9

What colour is phenolphthalein in acidic, neutral and alkaline solutions?

Answer 9

Acidic: colourless
Neutral: colourless
Alkaline: pink

Question 10

Finish the sentence: As the hydrogen ion concentration in a solution
increases by a factor of 10, …..

Answer 10

the pH of the solution
decreases by 1.

Question 11

What is a solution?

Answer 11

A mixture formed by a solute or a solvent.

Question 12

What is a solute?

Answer 12

The dissolved substance in a solution.

Question 13

What is a solvent?

Answer 13

The liquid in which the solute dissolves to form a solution.

Question 14

Concentration is a measure of the ____ or amount of ______ dissolved in a given volume of solvent or ________.

Answer 14

1. mass
2. solute
3. solution

Question 15

What is meant by a dilute solution?

Answer 15

A solution containing a relatively small amount of dissolved solute.

Question 16

What is meant by a concentrated solution?

Answer 16

A solution containing a relatively large amount of dissolved solute.

Question 17

What does it mean for a substance to dissolve?

Answer 17

The substance breaks up and mixes completely with a solvent to produce a solution.

Question 18

What is the dissociation of a molecule?

Answer 18

The breaking up of a molecule into ions when dissolved in water.

Question 19

Acids in solution are a source of _________ ions. The ions are produced when the acid __________ or breaks down to form ions.

Answer 19

1. hydrogen
2. dissociates

Question 20

What is the difference between how strong and weak acids dissociate into ions?

Answer 20

Strong acids completely dissociate into ions in solution, whereas weak acids only partially dissociate into ions in solution.

Question 21

Why does the metal need to be more reactive than hydrogen in the reactivity series for it to react with an acid?

Answer 21

In these reactions, the hydrogen ions in the acids are replaced by metal ions or ammonium ions.

Question 22

acid + metal → salt + _________

Answer 22

hydrogen

Question 23

Why are metal oxides and hydroxides bases?

Answer 23

They neutralise acids.

Question 24

acid + metal oxide → salt + ______

Answer 24

water

Question 25

acid + metal hydroxide → salt + ______

Answer 25

water

Question 26

acid + _______ → salt + water + carbon dioxide

Answer 26

carbonate

Question 27

What is neutralisation?

Answer 27

The reaction between an acid and a base to form a salt plus water.

Question 28

Describe an acid-alkali neutralisation reaction.

Answer 28

Hydrogen ions from the acid react with hydroxide ions from the alkali to form water:
H+(aq) + OH-(aq) → H2O(l)