Chemistry IGCSE > Section 4 > Flashcards

Section 4 Flashcards

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1
Q

how do alkali metals react when they are put in water?

A

they all react vigorously (in a similar way)

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2
Q

what does the reaction between alkali metals and water produce?

A

a metal hydroxide solution (which is alkaline)

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3
Q

why are group 1 elements known as the alkali metals?

A

because they form an alkaline metal hydroxide solution

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4
Q

what does the reaction of alkali metals with water also produce?

A

hydrogen - this is why you can see fizzing

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5
Q

which elements in group 1 are most reactive?

A

group 1 elements become more reactive down the group as the atomic number increases

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6
Q

how can you tell that alkali metals become more reactive?

A

the rate of reaction with water increases

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7
Q

name 3 alkali metals.

A

Lithium (Li), Sodium (Na), Potassium (Ka), Rubidium (Rb), Caesium (Cs), Francium (Fr)

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8
Q

what are the properties of alkali metals?

A
  • soft
  • low density
  • low melting point
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9
Q

what are the properties down the group of alkali metals?

A
  • they are more reactive
  • their boiling point decreases
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10
Q

why are alkali metals so reactive?

A
  • they all have one electron in their outer shell
  • further down the group the radium of the atoms get bigger
  • the outer shell is further away from the positive nucleus
  • positive nucleus holds outermost electron in place
  • the distance weakens the attractive force
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11
Q

how are group 7 elements called?

A

halogens

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12
Q

as the atomic number of halogens increases…

A
  • the less reactive
  • the elements have a darker colour
  • higher boiling point
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13
Q

which halogens are most reactive?

A

higher up group 7 elements are more reactive

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14
Q

whats the colour and physical state at room temperature of chlorine?

A
  • green
  • gas
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15
Q

whats the colour and physical state at room temperature of bromine?

A
  • red-brown
  • liquid
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16
Q

whats the colour and physical state at room temperature of iodine?

A
  • dark grey
  • solid
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17
Q

describe the boiling points of halogens.

A

the further down (the higher the atomic number) the higher the boiling point of the element

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18
Q

why are halogens further down less reactive?

A

they have more shells and the outer electrons are therefore further away from the positive nucleus meaning that the forces of attraction are weaker and its more difficult to gain another electron

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19
Q

which gases are found in the atmosphere?

A
  • carbon dioxide
  • oxygen
  • argon
  • nitrogen
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20
Q

how much argon is found in the atmosphere?

A

1%

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21
Q

how much oxygen is found in the atmosphere?

A

21%

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22
Q

how much nitrogen is found in the atmosphere?

A

78%

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23
Q

how much carbon dioxide is found in the atmosphere?

A

0.04%

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24
Q

what kind of gas is carbon dioxide?

A

a greenhouse gas

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25
exothermic reaction
chemical reactions which give out heat energy to the surrounding
26
what is the most common element in the air?
nitrogen
27
name the type of reaction that occurs when an acid reacts with an alkali
neutralisation
28
what does an acid + metal oxide produce?
salt + water
29
what does an acid + metal hydroxide produce?
salt + water
30
what does an acid + ammonia produce?
ammonium salt
31
when does iron corrode?
iron rusts when it is in contact with oxygen and water
32
what type of reaction takes place when iron corrodes?
oxidation reaction iron gains oxygen to form iron (III) oxide
33
what is the word equation for the reaction in which rust forms?
iron + oxygen + water = hydrated iron (III) oxide (rust)
34
what is a problem with rust?
it is a soft crumbly solid that soon flakes off to leave more iron available to rust again
35
what are the methods to prevent rusting?
barrier methods sacrificial method galvanising
36
alkali metals and oxygen react to form what?
metal oxdies
37
lithium and oxygen form
38
sodium and oxygen form
39
potassium and oxygen form
40
describe the colour change of halogens down the group
the colours of halogens get darker
41
describe the boiling points of halogens
the boiling point of halogens increase down the group
42
displacement reactions
more reactive halogens will displace less reactive ones
43
what happens if you add chlorine water to potassium iodide?
chlorine will react with potassium to form potassium chloride
44
burning magnesium
- burns with bright white flame - magnesium oxide forms (white powder) - magnesium oxide is alkaline when dissolved in water
45
burning hydrogen
- burns very easily / can be explosive - almost invisible pale blue flame - product is water vapour - squeaky pop
46
burning sulfur
- pale blue flame - produces sulfur dioxide - acidic when dissolved in water
47
thermal decomposition
break down of a substance into simpler substances when heated
48
what is produces when you heat a metal carbonate?
carbon dioxide and a metal oxide
49
colour of copper (II) carbonate
green
50
colour of copper (II) oxide
black
51
what happens if you heat copper (II) carbonate?
the green powder will decompose to form carbon dioxide and copper (II) oxide
52
thermal decomposition of copper (II) carbonate
- heat copper (II) carbonate then collect the gas that is given off in a test tube - the collected gas can then be tested to see if it is CO2 using the limewater test
53
what are three greenhouse gases ?
- water vapour - carbon dioxide - methane
54
what do greenhouse gases do?
they absorb most of the heat that would be radiated out into space, and re-radiate it in all directions - including back towards the earth
55
what human activities increase the amount of CO2 in the atmosphere?
DEFORESTATION: fewer trees means less CO2 is removed from the atmosphere via photosynthesis BURNING FOSSIL FUELS: carbon that was in these fuels is being released as CO2
56
what can climate change result in ?
flooding, sea level rise
57
what do some metals produce when reacting with acids?
salt + hydrogen
58
how metals react with acids tells you about their reactivity
the more reactive the metal, the faster the reaction will go
59
practical to investigate the difference in reactivity
1) set up 3 boiling tubes and fill them with equal volumes of dilute hydrochloric acid or sulfuric acid 2) place pieces of magnesium, zinc, iron in separate test tubes (same size and shape) 3) speed of reaction is indicated by rate at which bubbles of hydrogen are formed 4) hydrogen is confirmed by burning splint test (squeaky pop)
60
reactivity series
potassium sodium lithium calcium magnesium aluminium zinc iron copper silver gold
61
metals and acids react to produce what?
salt + hydrogen
62
give an example of a metal and an acid reacting
Na + HCl = NaCl + H
63
what is used to test for carbon dioxide?
limewater
64
what do we add to test for chloride, bromide or iodide ions (halides) ?
dilute nitric acid (through HCl) followed by silver nitrate solution
65
what happens if you add silver nitrate solution to chloride ions?
a white precipitate of silver chloride forms
66
what happens if you add silver nitrate solution to bromide ions?
a cream silver bromide precipitate forms
67
what happens if you add silver nitrate solution to iodide ions?
a yellow precipitate of silver iodide forms
68
how do you test for chlorine?
chlorine bleaches damp blue litmus paper, turning it white
69
how do you test for oxygen?
oxygen relights a glowing splint
70
how do you test for carbon dioxide?
co2 turns limewater cloudy - just bubble the gas through a test tube of limewater
71
how do you test for hydrogen?
hydrogen makes a "squeaky pop" with a lightened splint
72
where does the squeaky pop sound come from?
from the hydrogen burning with the oxygen in the air to form H2O
73
how do you test for ammonia?
ammonia turns damp red litmus paper blue
74
what colour does copper (II) sulfate have?
blue
75
what colour does dry copper (II) sulfate have?
white
76
what flame colour does lithium burn with?
red
77
what flame colour does sodium burn with?
yellow
78
what flame colour does potassium burn with?
lilac
79
what flame colour does calcium burn with?
orange
80
what flame colour does copper burn with?
blue-green
81
what tests is used to identify metal ions?
flame tests
82
how do you carry out the flame tests?
- clean a platinum wire loop by dipping it in HCl - then hold it in a flame - once it burns without any colour, dip into the sample - put it back in the clear blue part of the Bunsen flame
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