Rate of Reactions - Summary
- For substances to react with each other, their particles must collide and have enough energy to react.
- The minimum amount of energy that particles need to react of called activation energy.
- Increasing the temperature of a reaction makes it go faster - Particles have more energy and collide more often.
- Increasing the concentration of a solution makes a reaction go faster because the particles are closer together and so collide more often.
- Decreasing the size of pieces of a solid increasing its surface area. This makes a reaction go faster because there are more particles at the surface for the other reactant to collide with.
- A catalyst is a substance that changes the rate of a reaction without being used
- An enzyme is a biological catalyst - Catalysts also speed up chemical reactions (without altering it).
Reactant Particles - Move towards each other + collide
Product Particles - Move apart
Rate of reaction - Graph
Metals - Properties
- Metals in general have high electrical conductivity, high thermal conductivity, and high density. Typically they are malleable and ductile, deforming under stress without cleaving.
Reactions of metal with water
Lithium, Sodium, Potassium, Calcium and Magnesium all react with water to create their
(Li) (Na) (K) (Ca) (Mg)
hydroxides (LiOH, NaOH, KOH, CaOH, MgOH) and Hydrogen gas (H2).
Reaction of Magnesium with steam
Magnesium only visibly reacts with H2O when in the form of steam (water vapour).
Metals - Reactions with Acid
Some metals react with acid to form a salt (e.g. Sulfuric Acid = Sulfate) and hydrogen.
Magnesium - Magnesium + Sulphuric Acid --> Magnesium Sulphate + Hydrogen
Iron - Iron + Nitric Acid --> Iron Nitrate + Hydrogen
Copper does not react with acid because copper is below hydrogen in the activities series.
Displacement Reaction - A more reactive metal 'displaces' a less reactive metal from one of it's compounds
e.g. Copper Sulphate + Magnesium --> Magnesium Sulphate + Copper (Magnesium takes the sulphate)
We can work out if a displacement reaction will take place by looking at the reactivity of the metals being used for the experiment. If the metal is stronger than the compound, a reaction will take place, otherwise there will be no reaction
Blast Furnaces is used to get the oxygen out of the iron oxide in the ore (e.g. Haematite)
Rust is a chemical reaction that takes place on the surface of a metal - which is a type of corrosion.
An experiment involving 5 nails in identical test tubes proved that both oxygen and water must be present for rust:
Test Tube 1 - Dry Air and Calcium Chloride to absorb water -> No rust
Test Tube 2 - Nail under oil, with boiled water -> No rust
Test Tube 3 - Exposed to water and air -> Rust
Test Tube 4 - Nail + Salt Solution + Air -> Very rusty
Test Tube 5 - Acid Solution + Nail + Air -> Very Rusty
Rusting Protection - Protective Barrier
· Paint can prevent water and oxygen getting to the iron. It is also cheap and easily applied
· Oil and grease are flexible, so are suitable coatings for tools or machinery.
· Plastic coating, although more expensive, is strong and long lasting. Wire netting is coated with plastic to stop the plastic corroding.
· Tin plaiting, which is used to make the metal for ‘tin’ cans, are good for food containers, because the coating is strong, non-poisonous and stops corrosion.
· Electroplating applies a thin layer of protection to expensive metals using electricity, from metals such as chromium and nickel; it forms a tough, shiny coating. This is widely used on taps and cutlery.
Rusting Protection - Sacrificial Protection
· This method is used where painting is difficult or impossible
· It consists of the rusting metal being covered in a reactive metal like Magnesium or Zinc
· On railway lines, bags of magnesium are attached at regular intervals
· It works because the reactive metal corrodes, protecting the iron. This give it the name ‘Sacrificial Protection’
· It is used on oil rigs in the North Sea (Magnesium), the hulls of iron ships (Zinc), underground oil and gas pipes (Magnesium).
Magnesium and zinc are often used as sacrificial metals. They are more reactive than iron and lose their electrons in preference to iron, this is because of Magnesium and Zinc are high in the reactivity series.
Rusting Protection - Galvanising Pt 1
· This method involves the iron or steel, being dipped in molten zinc
· It is used in girders on bridges
· Some car body panels
· Motorway crash barriers
· Buckets and roofing nails
Rusting Protection - Galvanising Pt 2
Galvanising involves a physical barrier and a sacrificial protection
· The zinc keeps out air and water
· If the coating becomes scratched, the iron will still be protected because zinc is a more reactive metal
· Therefore, the zinc also sacrificially protects the iron
- Aluminium metal does not react with air.
- If the oxide layer is damaged, the aluminium metal is exposed to attack.
- Aluminium will burn in oxygen with a brilliant white flame to form the trioxide aluminium(III) oxide, Al2O3.Unlike iron and steel, aluminium does not rust or corrode in moist conditions.
- Its surface is protected by a natural layer of aluminium oxide. This prevents the metal below from coming into contact with air and oxygen.
Elements, Compounds and mixtures
Element - A substance that contains only one kind of atom. e.g. Carbon, Oxygen, Copper
Compound - A substance that contains atoms of more than one kind joined together e.g. Water, Carbon Dioxide.
Atoms: Atoms make up elements
- Some elements stay as single atoms, like Helium
- Some elements join their atoms in pairs, like Oxygen or Hydrogen. This is called a molecule
Elements and their symbols
Hydrogen - H Sodium - Na Iron - Fe
Helium - He Magnesium - Mg Silver - Ag
Lithium - Li Aluminium - Al Copper - Cu
Beryllium - Be Silicon - Si Bromine - Br
Boron - B Phosphorus - P Iodine - I
Carbon - C Sulphur - S Zinc - Zn
Nitrogen - N Chlorine - Cl
Oxygen - O Argon - Ar
Fluorine - F Potassium - K
Neon - Ne Calcium - Ca
Iron + Sulphur --> Iron Sulphide
Aluminium + Iodine --> Aluminium Iodide
Magnesium + Oxygen --> Magnesium Oxide
Sodium + Water --> Hydrogen + Sodium Hydroxide
Magnesium + Hydrochloric Acid --> Magnesium Chloride + Hydrogen
Hydrochloric = Chloride
Sulphuric = Sulphates
Nitric = Nitrates
Burning - A reaction with oxygen
When a metal is burnt, it is oxidised, and the product is the oxide of that metal
Copper + Oxygen --> Copper Oxide
Iron + Oxygen --> Iron Oxide (Rust)
Magnesium + Oxygen --> Magnesium Oxide
Non-metals can be oxidised too:
Carbon + Oxygen --> Carbon Dioxide
Sulphur + Oxygen --> Sulphur Dioxide
Burning Magnesium 1
A class experiment in which magnesium is weighed before the experiment, burnt (to form Magnesium Oxide), and weighed to see how much MgO was was made, and how much Mg was burnt.
- Total mass of products and reactants are the same - Conservation of Mass