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Chemistry - GCSE > States Of Matter and Mixtures, Chemical Changes > Flashcards

States Of Matter and Mixtures, Chemical Changes Flashcards

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1
Q

Solid to gas

A

Subliming

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2
Q

What happens to atoms during chemical reaction

A

Chemical changes happen when bonds from atoms break and the atoms change places. Atoms from the substances you start off with are rearranged to form different substances

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3
Q

How can you test the purity of a substance

A

By comparing the actual melting point to the expected value

Impure substances will melt over a range of temperatures as they are mixtures

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4
Q

What is simple distillation used for

A

Separating a liquid from a solution

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5
Q

When do you use fractional distillation

A

If you want to separate a mixture of liquids

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6
Q

When is filtration used

A

To separate a insoluble solid from a liquid

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7
Q

When is crystallisation used

A

To separate a soluble solid from a solution

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8
Q

What are two phases in chromatography

A

Mobile Phase - where the molecules can move. Always a liquid / gas
Stationary phase - where the molecules cant move. Solid or really thick liquid

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9
Q

Why do components in the mixture separate out in chromatography

A

Each of the chemicals in a mixture will spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase

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10
Q

What is a rf value

A

The ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent

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11
Q

How can water be purified

A

Filtration - wire mesh screens out large twigs and other rubble, and then gravel and sand beds filter any other solid bits
Sedimentation - iron or aluminium sulphate is added to the water, which makes the fine particles clump together and stick at the bottom
Chlorination - chlorine gas is bubbled through to kill harmful bacteria and other microbes

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12
Q

What do acids form in water

A

H+ ions

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13
Q

What does alkali form in water

A

OH- ions

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14
Q

Give 3 indictors for the PH scale

A

Litmus - red in acidic, purple in neutral, blue in alkali
Methyl orange - red in acidic, yellow in neutral and alkali
Phenolphthalein - colourless in acidic and neutral, pink in alkali

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15
Q

What is a neutralisation reaction

A

Acid + base = salt + water

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16
Q

What does ionise mean

A

An acid that splits up to produce a hydrogen ion, H+ and another ion

17
Q

What happens to strong acids in water

A

They ionise almost completely

18
Q

What happens to weak acids in a solution

A

They don’t fully ionise. This is a reversible reaction however

19
Q

What does the acid strength tell you

A

What proportion of acid molecules ionise in water

20
Q

What is a concentrated acid like

A

An acid with a large number of acid molecules compared to the volume of water. The reverse of this is a dilute acid

21
Q

What happens when a acid and a metal oxide/hydroxide react

A

It makes salt + water

22
Q

What happens when an acid and metal/ metal carbonate react

A

(Metal) makes salt + hydrogen ,whereas (metal carbonate) makes salt, water + carbon dioxide

23
Q

What substances are soluble in water

A

Common salts of sodium, potassium and ammonium
Nitrates
Common chlorides (apart from silver chloride and lead chloride)
Common sulphates ( apart from lead, barium and calcium sulphate)

24
Q

What substances are not soluble in water

A

Common carbonates and hydroxides (apart from sodium, potassium and ammonium ones)

25
Q

How would you make a soluble salt

A

React an acid that contains one of the ions you want in the salt with an insoluble base that contains the other ion that you need ( often a metal oxide or metal hydroxide)

They can also be made by reacting a acid with an alkali

26
Q

What is electrolysis

A

The breaking down of a substance using electricity

27
Q

What occurs to the electrons in electrolysis

A

Oxidisation (loss of electrons) reduction (gain of electrons)

28
Q

Where do positive ions move in the electrolyte

A

The positive ions (cations) move towards the cathode (negative electrode) and gain electrons. Negative ions do the opposite

29
Q

Why cant a ionic solid be electrolysed

A

Because the ions are in fixed positions and cant move

30
Q

Why can molten ionic compounds be electrolysed

A

Because the atoms can move freely and conduct electricity

Chemistry - GCSE (6 decks)

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