2 A,B,C,D Flashcards
Group 1 alkali metals
Lithium, sodium, potassium
Understand how the similarities in the reactions of these elements with water provide evidence for the recognition as a family of elements
fizzing (hydrogen is produced)
metal floats and moves around on the water
metal disappears
In each case a metal hydroxide solution is produced.
Act vigorously with water
These similarities in the reactions provide evidence that the 3 metals are in the same group of the Periodic Table (i.e. have the same number of electrons in their outer shell).
Understand how the differences between the reactions of these elements with air and water provide evidence for the trend in reactivity in group 1
Lithium: less reactive
fizzing (hydrogen gas is released)
lithium floats and moves around on the water
lithium disappears
Sodium: median reaction fizzing (hydrogen gas is released) sodium floats and moves around on the water sodium melts into a silver-coloured ball sodium disappears
Potassium: the most reactive fizzing (hydrogen gas is released) potassium floats and moves around on the water catches fire with a Lilac flame potassium disappears
When the group 1 metals react with air they oxidise, showing a similar trend in reactivity as we go down the group of the Periodic Table.
Use knowledge of trends in group 1 to predict the properties of other alkali metals
As the reactivity of Alkali Metals increases down the Group, Rubidium, Caesium and Francium will react more vigorously with Air and Water
Lithium is at the top so will be the least reactive, while Francium is at the bottom so will be the most reactive (Francium is rare and radioactive so is difficult to confirm predict reaction)
Rubidium- explodes with sparks
Caesium- violent explosion due to rapid production of heat and hydrogen
Francium- too reactive
Group 7 Halogens
F2. Cl2 Br2 I2 At2
Use knowledge of trends in group 7 to predict the properties of other halogens
As you go down the group: Colour becomes darker From gas it turns to solid Melting and boiling point increases The reactivity decreases
Understand how displacement reactions involving halogens and halides provide evidence for the trend in reactivity in group 7
A more reactive halogen will displace a less reactive halogen, e.g. chlorine will displace bromine
By reacting a halogen solution with a potassium halide solution and making observations, the order of their reactivity can be deduced
Top layer: pink - I2
Top layer: orange - Br2
Top layer: colourless - Cl2
When one of the halogens goes alone they always have a (small)2 next to them.
Oxidation is loss of electrons.
Reduction is gain of electrons.
Gases in the atmosphere
Nitrogen Oxygen Argon Carbon dioxide Water vapour
Know the approximate percentages by volume of the four most abundant gases in dry air.
Nitrogen, N2 - 78%-79% Oxygen, O2 - 20%-21% Argon, Ar - 1% (approx.) Carbon dioxide, CO2 - 0.03 (approx.) Water vapour, H2O variable amounts
Understand how to determine the percentage by volume of oxygen in air using experiments involving the reactions of metals (e.g. iron) and non-metals (e.g. phosphorus) with air
- Copper:
The copper is in excess and uses up the oxygen to form copper oxide (CuO).
All the oxygen in the air is therefore used up, and so the volume of the air decreases by about 20% (the percentage of oxygen in air).
Copper + oxygen - copper oxide
2Cu + O2 - 2CuO
- Iron:
The iron reacts with the oxygen in the air (rusting).
As long as the iron and water are in excess, the total volume of air enclosed by the apparatus decreases by about a fifth (20%) over several days.
Iron + Oxygen + Water - hydrated iron (III) oxide (rust)
- Phosphorus:
The phosphorus is lit with a hot wire.
It reacts with the oxygen in the air and causes the water level in the bell jar to rise by about 20%.
Phosphorus + oxygen - Phosphorus oxide
Describe the combustion of elements in oxygen, including magnesium, hydrogen and sulphur
- Magnesium reacts with oxygen producing a bright white flame leaving behind a white ash of magnesium oxide.
Magnesium + oxygen → Magnesium oxide 2Mg (s) + O₂ (g) → 2MgO
MgO is a base, which can react with an acid to give a salt and water.
- Hydrogen reacts with oxygen in an explosive reaction. This is the basis of the ‘squeak pop’ test for hydrogen in test tube. With larger quantities of hydrogen this explosion can be dangerous.
hydrogen + oxygen → water 2H₂ (g) + O₂ (g) → 2H₂O (l)
- Sulfur reacts with oxygen producing a blue flame.
sulfur + oxygen → sulfur dioxide S (s) + O₂ (g) → SO₂ (g)
When sulfur dioxide (SO₂) dissolves in water it forms an acidic solution of sulfurous acid:
SO₂ (g) + H₂O (l) Sulfur reacts with oxygen producing a blue flame.
sulfur + oxygen → sulfur dioxide
S (s) + O₂ (g) → SO₂ (g)
Describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper (II) carbonate
In thermal decomposition a compound is broken down into simpler compounds by the action of heat.
Eg- CuCO3(s) → CuO(s) + CO2(g)
Green. Black
Observation: green powder (CuCO3) changes to a black powder (CuO)
Know that carbon dioxide is a greenhouse gas and that increasing amounts in the atmosphere may contribute to climate change
Carbon dioxide (CO2) is a greenhouse gas.
It absorbs infra-red radiation and therefore warms the atmosphere. This leads to global warming.
This may cause climate change.
Explanation:
Sun emits short wave radiation (ultraviolet radiation) that enters the Earth’s atmosphere
Earth’s surface absorbs short wave radiation from the sun and re-emits it as long wave radiation (infrared/heat)
Greenhouse gases - such as Carbon Dioxide, absorb and re-radiate this long wave radiation, retaining heat within the atmosphere
Earth’s average temperature rises as a result
Practical: determine the approximate percentage by volume of oxygen in air using metal or non-metal
The same as the copper, iron and phosphorus
Reactivity series
Potassium Sodium Lithium Calcium Magnesium Aluminium (Carbon) Zinc Iron Tin Lead (Hydrogen) Copper Silver Gold Platinum
Metals and steam
Ca reacts with cold water: Ca(s) + H2O(I) - Ca(OH)2 (aq) + H2(g)
Know the colours, physical states (at room temperature) and trends in physical properties of these elements
Colours: State: Mpt/Bpt: Reactivity:
F2. Yellow. Gas. IN. DE
Cl2. Greenish-yellow Gas. CR. CR
Br2. Red. Liquid EA. EA
I2. Grey. Solid. SI. SI
At2 Dark grey/ black Solid. NG. NG
At room temperature (20C℃), the physical state of Halogens become harder and more set as you go down the Group.
Halogens become darker as you go down the Group.
Understand how metals can be arranged in a reactivity series based on their displacement reactions between: metals and metals oxides, metals and aqueous solutions of metal salts
A metal will displace another metal from its oxide that is lower in the reactivity series. For example, a reaction with magnesium and copper (II) oxide will result in the magnesium displacing the copper from its oxide:
Magnesium + copper (II) oxide - magnesium oxide + copper
Mg + CuO - MgO + Cu
A metal will also displace another metal from its salt that is lower in the reactivity series. For example, the reaction between zinc and copper (II) sulfate solution will result in zinc displacing the copper from its salt:
Zinc + copper sulphate - Zinc sulphate + copper
Zn (s) + CuSO4 (aq) - ZnSO4 (aq) + Cu(s)
The blue colour of the copper (II) sulfate solution fades as colourless zinc sulfate solution is formed.
Know the order of the reactivity series
Potassium Sodium Lithium Calcium Magnesium Aluminium (Carbon) Zinc Iron Tin Lead (Hydrogen) Copper Silver Gold Platinum
Know the conditions under which iron rusts
Iron rusts when oxygen and water are present.
Reaction:
Iron + oxygen + water - hydrated iron (III) oxide (rust)
4Fe + 3O2 + nH2O - 2Fe203.nH2O
Understand how the rusting of iron may be prevented by barrier methods, galvanising and sacrificial protection
Barrier Methods: Rusting may be prevented by stopping the water and oxygen getting to the iron with a barrier of grease, oil, paint or plastic.
Coat oil/grease: adv- cheap disadvantage-dirty and wears of easily
Eg- machine parts
Coat in paint: adv- looks attractive and cheap disadvantage- scratches easily
Eg- bridges, cars
Coat in plastic: adv- transparent disadvantage- only suitable for small items
Eg- pin badges
Coat in a metal less reactive than Fe: adv- more hard wearing than the other barrier methods disadvantage- can also eventually be scratched
Eg- food cans
Galvanising: This is a process where an object made of iron is totally coated in zinc metal.
This is used for objects such as buckets and nails. Zn is more reactive than Fe.
The Zn reacts with oxygen and water in preference to the Fe. The Zn forms Zn2+ ions when it reacts and it releases electrons: Zn2+ + 2e-
These electrons move throughout the metal object and they ensure that this reaction: Fe- Fe2+ 2e- never happens.
Sacrificial protection: This is when blocks of Mg or Zn are attached to an iron object e.g- a ship or a pipe-line.
The more reactive metal (Zn or Mg) reacts with oxygen and water in preference to the iron.
So this reaction occurs: Zn- Zn2+ + 2e-
But this reaction will not occur: Fe- Fe2+ + 2e-
Understand the terms: oxidation, reduction, redox,oxidising agent, reducing agent. In terms of gain or loss of oxygen and loss or gain of electrons
Oxidation:
Oxidation is the loss of electrons. For example a sodium atom (Na) loses an electron to become a sodium ion (Na⁺).
Another definition of oxidation is the gain of oxygen. For example if carbon combines with oxygen to form carbon dioxide, the carbon is being oxidised.
Reduction:
Reduction is the gain of electrons. For example a sodium ion (Na⁺) gains an electron to become a sodium ion (Na).
Another definition of reduction is the loss of oxygen. For example when aluminium oxide is broken down to produce aluminium and oxygen, the aluminium is being reduced.
Redox: A reaction involving oxidation and reduction.
A good way to remember the definitions of oxidation and reduction in terms of electrons is:
OILRIG : Oxidation Is the Loss of electrons and Reduction Is the Gain of electrons
Oxidising agent: A substance that gives oxygen or removes electrons (it is itself reduced).
Reducing agent: A substance that takes oxygen or gives electrons (it is itself oxidised).
Practical: investigate reactions between dilute hydrochloric and sulphuric acids and metals (e.g. Magnesium, zinc and iron)
Metals which are above hydrogen in the reactivity series will react with dilute hydrochloric or sulfuric acid to produce a salt and hydrogen.
metal + acid → salt + hydrogen
For example:
magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
This is a displacement reaction.
There is a rapid fizzing and a colourless gas is produced. This gas pops with a lighted splint, showing the gas is hydrogen.
The reaction mixture becomes warm as heat is produced (exothermic).
The magnesium disappears to leave a colourless solution of magnesium chloride.
If more reactive metals are used instead of magnesium the reaction will be faster so the fizzing will be more vigorous and more heat will be produced.
Understand how metals can be arranged in the reactivity series based on their reactions with water and dilute hydrochloric or sulfuric acid
- K, Na, Li and Ca react with cold water
- Mg reacts slowly with cold water, reacts quickly with steam to give oxide.
- K, Na, Li, Ca, Mg, Al, (C), Zn and Fe react with acid
- (H), Cu, Ag and Au do not react with acid
