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HCHS GCSE Science 2 - Chemistry > Section 3 - Cemical Changes > Flashcards

Section 3 - Cemical Changes Flashcards

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1
Q

What is the pH scale?

A

A measure of how alkaline or acidic a solution is.

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2
Q

Where are acids on the pH scale?

A

Below 7.

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3
Q

Where are alkalis on the pH scale?

A

Above 7.

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4
Q

What is a base?

A

A substance that reacts with an acid to make a salt.

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5
Q

What is an acid?

A

A substance that reacts with base to make a salt.

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6
Q

What is an alkali?

A

A base that is soluble in water.

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7
Q

How can pH be measured?

A

Using indicators or electronic testing devices.

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8
Q

How does the concentration of hydrogen change through the pH scale?

A

The lower the pH the higher the concentration of hydrogen.

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9
Q

Where is neutral on the pH scale?

A

7

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10
Q

What is an Indicator?

A

A dye that changes colour due to pH.

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11
Q

What colours does universal indicator become? At what pHs?

A

Reds in acidic solutions, green when neutral and purple when alkaline.

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12
Q

What colours does litmus become? At what pHs?

A

Red in acids, purple when neutral and blue when alkaline.

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13
Q

What colours does methyl orange become? At what pHs?

A

Red in acids and yellow when neutral.

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14
Q

What colours does phenolphthalein become? At what pHs?

A

Colourless and clear in acidic or neutral solutions but pink in alkalis.

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15
Q

What is the reaction between an acid and a base called?

A

Neutralisation.

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16
Q

Where do neutralisation reactions occur?

A

In aqueous solutions.

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17
Q

What are the products of neutralisation? What pHs are they?

A

Salts and water, both are a pH of 7.

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18
Q

What do all acids do in water?

A

Ionise, or dissociate, forming a hydrogen ion and another ion.

19
Q

What does an acid’s strength mean?

A

What proportion of the acid molecules ionise in water.

20
Q

If an acid is weak, what does it mean?

A

A small proportion of the acid molecules ionise in water.

21
Q

If an acid is strong, what does it mean?

A

A large proportion of the acid molecules ionise in water.

22
Q

What type of reaction is the ionisation of a weak acid? What does this form?

A

The reaction is reversible, this creates an equilibrium.

23
Q

What is concentration in acids?

A

The amount of acid per litre.

24
Q

How does an acids concentration effects its pH?

A

If the concentration of hydrogen ions changes by a factor of ten, the pH changes by one inversely.

25
Q

What happens when a metal reacts with an acid?

A

It produces salt and hydrogen.

26
Q

What happens when a metal carbonate reacts with an acid?

A

It produces salt, water and carbon dioxide.

27
Q

How can carbon dioxide be tested for using limewater?

A

The limewater changes colour from clear to cloudy yellow when carbon dioxide is bubbled through it.

28
Q

Are common chlorides soluble?

A

Yes, except silver chloride and lead chloride.

29
Q

Are common sulfates soluble?

A

Yes, except lead, barium and calcium sulfate.

30
Q

Are common carbonates and hydroxides soluble?

A

No, except those of sodium, potassium and ammonium.

31
Q

Are common salts of sodium potassium and ammonium soluble.

A

Yes.

32
Q

Are nitrates soluble?

A

Yes.

33
Q

How are insoluble salts made?

A

Precipitation reactions.

34
Q

What is electrolysis?

A

The breaking down of a substance using electricity.

35
Q

What is oxidation?`

A

The loss of electrons in a reaction.

36
Q

What is a reduction reaction?

A

Gaining electrons in a reaction.

37
Q

How does electrolysis work?

A

By passing an electric current through a electrolyte, causing it to decompose.

38
Q

What is an electrolyte?

A

A molten or dissolved ionic compound.

39
Q

What makes up an electrochemical cell?

A

A cathode, anode, d.c power supply and an electrolyte.

40
Q

In electrolysis, what happens to the ions?

A

They head to either electrode depending on charge.

41
Q

In electrolysis, where do positive ions head?

A

Towards the cathode.

42
Q

In electrolysis, where do negative ions head?

A

Towards the anode.

43
Q

In electrolysis of an aqueous solution, how could hydrogen gas form?

A

Provided hydrogen ions are present and the metal is more reactive than hydrogen then hydrogen gas begins to form at the cathode.

44
Q

In electrolysis of an aqueous solution, how could oxygen be formed?

A

Provided no halide ions are present then oxygen will form at the anode.

HCHS GCSE Science 2 - Chemistry (9 decks)

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