Section 4 Flashcards
how do alkali metals react when they are put in water?
they all react vigorously (in a similar way)
what does the reaction between alkali metals and water produce?
a metal hydroxide solution (which is alkaline)
why are group 1 elements known as the alkali metals?
because they form an alkaline metal hydroxide solution
what does the reaction of alkali metals with water also produce?
hydrogen - this is why you can see fizzing
which elements in group 1 are most reactive?
group 1 elements become more reactive down the group as the atomic number increases
how can you tell that alkali metals become more reactive?
the rate of reaction with water increases
name 3 alkali metals.
Lithium (Li), Sodium (Na), Potassium (Ka), Rubidium (Rb), Caesium (Cs), Francium (Fr)
what are the properties of alkali metals?
- soft
- low density
- low melting point
what are the properties down the group of alkali metals?
- they are more reactive
- their boiling point decreases
why are alkali metals so reactive?
- 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
how are group 7 elements called?
halogens
as the atomic number of halogens increases…
- the less reactive
- the elements have a darker colour
- higher boiling point
which halogens are most reactive?
higher up group 7 elements are more reactive
whats the colour and physical state at room temperature of chlorine?
- green
- gas
whats the colour and physical state at room temperature of bromine?
- red-brown
- liquid
whats the colour and physical state at room temperature of iodine?
- dark grey
- solid
describe the boiling points of halogens.
the further down (the higher the atomic number) the higher the boiling point of the element
why are halogens further down less reactive?
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
which gases are found in the atmosphere?
- carbon dioxide
- oxygen
- argon
- nitrogen
how much argon is found in the atmosphere?
1%
how much oxygen is found in the atmosphere?
21%
how much nitrogen is found in the atmosphere?
78%
how much carbon dioxide is found in the atmosphere?
0.04%
what kind of gas is carbon dioxide?
a greenhouse gas
exothermic reaction
chemical reactions which give out heat energy to the surrounding
what is the most common element in the air?
nitrogen
name the type of reaction that occurs when an acid reacts with an alkali
neutralisation
what does an acid + metal oxide produce?
salt + water
what does an acid + metal hydroxide produce?
salt + water
what does an acid + ammonia produce?
ammonium salt
when does iron corrode?
iron rusts when it is in contact with oxygen and water
what type of reaction takes place when iron corrodes?
oxidation reaction
iron gains oxygen to form iron (III) oxide
what is the word equation for the reaction in which rust forms?
iron + oxygen + water = hydrated iron (III) oxide (rust)
what is a problem with rust?
it is a soft crumbly solid that soon flakes off to leave more iron available to rust again
what are the methods to prevent rusting?
barrier methods
sacrificial method
alkali metals and oxygen react to form what?
metal oxdies
lithium and oxygen form
sodium and oxygen form
potassium and oxygen form
boiling point of chlorine
-34°C
boiling point of bromine
59°C
boiling point of iodine
185°C
describe the colour change of halogens down the group
the colours of halogens get darker
describe the boiling points of halogens
the boiling point of halogens increase down the group
displacement reactions
more reactive halogens will displace less reactive ones
what happens if you add chlorine water to potassium iodide?
chlorine will react with potassium to form potassium chloride
burning magnesium
- burns with bright white flame
- magnesium oxide forms (white powder)
- magnesium oxide is alkaline when dissolved in water
burning hydrogen
- burns very easily / can be explosive
- almost invisible pale blue flame
- product is water vapour
- squeaky pop
burning sulfur
- pale blue flame
- produces sulfur dioxide
- acidic when dissolved in water
thermal decomposition
break down of a substance into simpler substances when heated
what is produces when you heat a metal carbonate?
carbon dioxide and a metal oxide
colour of copper (II) carbonate
green
colour of copper (II) oxide
black
what happens if you heat copper (II) carbonate?
the green powder will decompose to form carbon dioxide and copper (II) oxide
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
what are three greenhouse gases ?
- water vapour
- carbon dioxide
- methane
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
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
what can climate change result in ?
flooding, sea level rise
what do some metals produce when reacting with acids?
salt + hydrogen
how metals react with acids tells you about their reactivity
the more reactive the metal, the faster the reaction will go
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)
reactivity series
potassium
sodium
lithium
calcium
magnesium
aluminium
zinc
iron
copper
silver
gold
metals and acids react to produce what?
salt + hydrogen
give an example of a metal and an acid reacting
Na + HCl = NaCl + H
