Unit 3 - Chemistry In Society Flashcards
Metallic bond definition
A metallic bond is the electrostatic force of attraction between positively charged ions and delocalised electrons.
Matallic bond properties
Metallic elements can conduct electricity in any state.
This is because they have delocslised electrons (free to move).
Thermosoftening plastic
Thermosoftening plastics will melt when heated, so they can be reshaped, reused and recycled.
Thermosetting plastics
Thermosetting plastics can be reshaped as they are made and then permanently set. They cannot be reshaped, reused or recycled.
(E.g. kettles, plugs)
What do all monomers units contain?
A carbon to carbon double bond.
Monomers are alkene based and are unsaturated molecules.
What are polymers?
Polymers are long chained molecules which are made by joining monomers together.
Polymers are examples of plastics.
How are polymers made?
Polymers are made when lots of single unit monomers join together.
The reaction is called addition polymerisation.
A lot of energy is needed. It is often carried out at high pressure with a catalyst.
Addition polymerisation definition
Addition polymerisation is a chemical reaction that involves making a polymer through an addition reaction.
The polymer is made from unsaturated monomers joining together in long chains.
(Polymers are made when lots of single unit monomers join together).
Monomer definition
A monomer is a small molecule that can be joined together to form a polymer.
Repeating unit
The repeating unit is the shortest repeating section of the polymer.
Radioactive decay
Radioactive decay is when unstable nuclei become stable by giving out alpha, beta or gamma radiation.
Heavier isotopes are more unstable and so are more likely to be radioactive.
What are unstable nuclei called?
Radioisotopes
To become stable radioisotope undergo radioactive decay.
Alpha radiation/ particles properties
It is a positively charged particle so is attracted to negative plate.
Can only travel a few cm and are easily stopped by a piece of paper.
Beta particles/ radiation properties
(Caused when a neutron breaks down.)
Beta particles are electrons given out by the nucleus of an atom - has a negative charge and is attracted to a positive plate.
Can travel about 1m in air but can be stopped by 5mm of aluminium.
Gamma rays/ radiation properties
They are electromagnetic waves so are not affected by any charged plates.
They can travel long distances and can be stopped by 25mm of lead.
What are alpha particles
Alpha particles consist of 2 protons and 2 neutrons and have a positive charge. (Charge = 2+)
It is the nucleus of a helium atom.
What are beta particles?
Beta particles are electrons ejected from the nucleus of an atom.
What are gamma rays
Gamma rays are electromagnetic waves emitted from within the nucleus of an atom.
Half-life definition
Half-life is the time taken for the radioactivity of a substance to fall to half of it’s original value.
Uses of radioisotopes
Medicine - sterilising equipment, cancer treatment, used as a tracer in diagnostics.
Industry - used in smoke alarms, to ensure the thickness of paper, detect leaks.
Used to date materials.
Isotopes used in medicine are usually beta or gamma as they have short half-lives so they don’t stay in the patient too long.
In Industry, they tend to have much longer half-lives.
What is the half-life of an isotope effected by?
The half-life of an isotope is constant. It is unaffected by chemical or physical conditions.
Importance of fertilisers
Fertilisers are used to provide plants with the essential elements for growth. They restore essential nutrients in the soil.
Elements found in fertilisers
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Ammonia properties
Clear, colourless gas
Pungent smelling
Very soluble - makes an alkaline solution.
Ammonia solution + acid —> ammonium salt + water
What is ammonia?
Ammonia is nitrogen hydride (NH3) which is used to make fertilisers.
Ammomia reaction
Ammonia solution + acid –> ammonium salt + water
What is produced in the haber process?
Ammonia (NH3)
Haber process balanced equation
H2(g) + 3N2(g) 2NH3(g)
Conditions used in the haber process
The haber process uses moderate temperatures.
- (too low then the reaction is too slow, too high then too fast and so a reverse reaction takes place)
High pressure
An iron catalyst is used
Ostwald process
Product - nitric acid
Reactant - ammonia, oxygen and water
Catalyst - platinum
Equations for the reactions of metals
Metal + oxygen –> metal oxide
Metal + water –> metal hydroxide + hydrogen
Metal + dilute acid –> salt + hydrogen
What happens when metals combine
They form alloys.
Redox reaction definition
A redox reaction is when an oxidation and reduction reaction take place at the same time.
Oxidation definition
Oxidation - loss of electrons by a reactant
O - oxidation I - is L - loss R - reduction I - is G - gain
Reduction definition
Reduction - gain of electrons by a reactant.
O - oxidation I - is L - loss R - reduction I - is G - gain
Extraction of metal
The higher up a metal is on the electrochemical series, the harder it is to extract the metal from its ore.
During extraction the metal ions are REDUCED to metal atoms.
Extracting metals - heat alone
Some metals can be extracted from their ore (metal oxide) bu heat alone. This is only the case for the least reactive metals.
- Silver (Ag)
- Gold (Au)
- Mercury (Hg)
Extracting metals - heat and carbon
The heat and carbon caused the metal to be displaced and the carbon to join up with the oxygen.
The carbon is called a reducing agent.
- copper (Cu)
- lead (Pb)
- iron (Fe)
- tin (Sn)
- zinc (Zn)
Extracting metals - electrolysis
Any metal above aluminium (Al) on the electrochemical series is attracted by electrolysis.
The positive metal ion is attracted to the negative electrode where it gains electrons to turn back into a metal atom.
Electrolysis
Electrolysis is the process of separating a compound into its elements using electric current.
A D.C. Power supply is used so that the products can be identified and collected.
The negative ions go to the positive electrode.
The positive metal ions go to the negative electrode where they gain electrons and turn back into a metal atom.
Any metal from Al upwards in the E.C.S is extracted by electrolysis.
Electrolyte definition
Electrolyte is a solution (ionic compound) that contains ions which can conduct electricity.
What is needed to make a basic electrochemical cell
2 different metals and an electrolyte.
What is the use of an ion bridge?
The salt/ion bridge is used to complete the circuit by linking the 2 half cells.
Voltage - electrochemical series
The further apart the metals an the ECS, the greater the voltage that would be produced l.
