Topic 3 - Chemical Changes Flashcards Preview

GCSE Chemistry Edexcel Grade 9-1 course > Topic 3 - Chemical Changes > Flashcards

Flashcards in Topic 3 - Chemical Changes Deck (122)
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1

What is the pH scale?

The pH scale is how acidic or alkaline a solution is.

2

What is the pH of a neutral substance?

A neutral substance has a pH of 7.

3

What is an acid?

An acid is a substance with a pH of less than 7.

4

What ions do acids form in water?

H+ ions

5

What happens as the concentration of hydrogen ions increases in a solution?

It becomes more acidic - the pH decreases.

6

What happens to the concentration of hydrogen ions as the solution becomes more acidic and the pH decreases?

The concentration of hydrogen ions increases

7

What is a base?

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

8

What is an alkali?

An alkali is a base that is soluble in water.

9

What do all alkalis have a pH of?

All alkalis have a pH of more than 7.

10

What do alkalis form in water?

Hydroxide (OH ⁻) ions.

11

What happens to the concentration of hydroxide ions as the pH increases in a solution?

It increases.

12

What happens as the concentration of hydroxide ions increases in a solution?

The pH increases.

13

What is an indicator?

An indicator is a dye that changes colour depending on whether it's above or below a certain pH.

14

What are the four indicators you need to know about?

Universal indicator
Litmus
Methyl orange
Phenolphthalein

15

What colour is litmus in acidic solutions?

Red

16

What colour is litmus in neutral solutions?

Purple

17

What colour is litmus in alkaline solutions?

Blue

18

What colour is Methyl orange in acidic solutions?

Red

19

What colour is Methyl orange in neutral solutions?

Yellow

20

What colour is Methyl orange in alkaline solutions?

Yellow

21

What colour is Phenolphthalein in acidic solutions?

Colourless

22

What colour is Phenolphthalein in neutral solutions?

Colourless

23

What colour is Phenolphthalein in alkaline solutions?

Pink

24

What is a reaction between an acid and an alkali called?

Neutralisation

25

What does neutralisation produce?

A salt and water

26

When an acid neutralises a base (or a base neutralises an acid) what pH are the products?

The products are neutral (pH 7).

27

At pH 7, what are the concentrations of hydrogen ions and hydroxide ions?

The concentrations of hydrogen ions and hydroxide ions are equal.

28

What are some examples of strong acids?

Sulfuric acid, hydrochloric acid, and nitric acid.

29

What does dissociate mean?

Ionise

30

Do strong or weak acids ionise completely in water?

Strong acids, weak acids do not fully ionise in solution.