Unit 4-Chemical changes Flashcards Preview

Chemistry Gcse AQA 9-1 > Unit 4-Chemical changes > Flashcards

Flashcards in Unit 4-Chemical changes Deck (54):
1

What is the PH scale?

A measure of how acidic or alkaline a solution is.

2

The lower the PH of a solution...

The more acidic it is.

3

The higher the PH of a solution is...

The more alkaline it is.

4

What is neutral if the PH scale?

7

5

What is the most alkaline you can get on the PH scale?

14

6

What is the most acidic you can get on the PH scale?

0

7

What is an indicator?

A dye that changes colour depending on whether it’s above or below a certain PH.

8

What are the two main types of indicator?

-Litmus paper.
-Universal indicator.

9

What is more accurate than an indicator for measuring PH?

A PH probe.

10

Why is a PH probe more accurate than an indicator?

It gives a numerical value.

11

What is an acid?

A substance that forms an aqueous solution with a PH of less than 7.

12

What type of ions do acids form in water?

H+ ions.

13

What is a base?

A substance with a PH greater than 7.

14

What is an alkali?

A base that dissolved in water to form a solution with a PH greater than 7.

15

What ions do alkalis form in water?

OH- ions.

16

What is neutralisation?

A reaction between an acid and an alkali that gives PH 7.

17

What is the formula for neutralisation?

Acid + base = salt + water

18

What is the neutralisation reaction in terms of H and OH ions?

Hpositive + OHnegative = H20

19

What do titrations allow you to do?

They allow you to find out exactly how much acid is needed to neutralise a quantity of alkali.(or other way round)

20

How do you carry out a titration reaction?(6 marker).

1)Add a set volume of the alkali into a conical flask.
2)Add a few drops of indicator.
3)Use a funnel to fill a buttered with some acid of known concentration.
4)Make sure you do this below eye.
5)Record the initial volume of the acid in the butter.
6)Using the burette add the acid to the alkali a bit at a time.
7)The indicator will change colour.
8)Record the final volume of the acid in the burette and use this to calculate the volume of acid used to neutralise the alkali.

21

How do you increase the accuracy of the titration?

Repeat for several consistent readings.

22

What are anomalous results?

Results that don’t fit in with the rest.

23

Do acids ionise in aqueous solutions?

Yes.

24

What does HCL produce when it ionises in an aqueous solution?

HCL= Hpositive + Clminus

25

What happens when a strong acid is added to water?

-It ionises completely.
-All acid particles dissociate to release H+ ions.

26

What happens when weak acids are added to water?

-They don’t fully ionise.
-Only a small amount of acid particles dissociate to release H+ ions.

27

Is the ionisation of a weak acid or a strong acid a reversible reaction?

A weak acid.

28

Why are strong acids more reactive than weak acids?

The concentration of H+ ions is higher so the rate of reaction is faster.

29

Is a metal oxide reacts with an acid what does it produce?

Salt and water.

30

If a metal hydroxide reacts with an acid what does it produce?

Salt and water.

31

If a metal carbonate reacts with an acid what does it produce?

Salt , water and carbon dioxide.

32

What is the reactivity series?

A list of metals in order of their reactivity towards other substances.

33

How are metals reactivity determined ?

By how easily they lose electrons.

34

What are the top four elements in the reactivity series?

-Potassium.
-Sodium.
-Lithium.
-Calcium.

35

How is the speed of a reaction determined?

By the rate of which the bubbles of hydrogen are given off.

36

What happens when a metal reacts with water?

It produces metal hydroxide and hydrogen.

37

What is oxidation?

When a metal reacts with oxygen.

38

What is a reduction reaction?

A reaction that separates a metal from its oxide.

39

What is an ore?

A type of rock that contains metal compounds.

40

What is the mnemonic to remember when to use oxidation or reduction? (With electrons)

Oxidation
Is
Loss
Reduction
Is
Gain

41

Oxidation=?

The gain of oxygen.

42

Reduction=

The loss of oxygen.

43

What is oxidation in terms of electrons?

The loss of electrons.

44

What is reduction in terms of electrons?

The gain of electrons.

45

What is a displacement reaction?

When a metal ions gains electrons and is reduced. The metal atoms always loses electrons and is oxidised.

46

What is electrolysis?

When an electric current is passed through an electrolyte to create a flow of charge.

47

What is an electrolyte?

A liquid or solution that can conduct electricity.

48

Can an ionic solution be electrolysed?

No.

49

Why can an ionic solution not be electrolysed?

The ions can’t move.

50

At the negative electrode what happens in electrolysis?

Reduction.

51

At the positive electrode what happens in electrolysis?

Oxidation.

52

How do you test for chlorine?

It bleaches litmus paper.

53

How do you test for hydrogen.

It makes a squeaky pop with a lighted splint.

54

How do you test for oxygen?

It relights a glowing splint.