S4 - Chemistry Test (2) Flashcards
What are polymers?
Giant molecules formed when lots of small molecules join together
How are alkene monomers made?
By cracking long-chain alkanes
What are the properties of poly(ethene) and what is it used for?
- Cheap
- Strong
- Plastic bags and bottles
What are the properties of poly(propane) and what is it used for?
- Strong
- High elasticity
- Crates and ropes
What are the properties of poly(chloroethene) and what is it used for?
- Rigid
- Building materials: drain pipes & insulating wiring
What properties to polymers generally have?
- Light
- Don’t break
- Don’t rot
- Don’t conduct electricity
- Thermoplastic - can be melted and made into other shapes
- Thermoset - will not melt after forming
What are alloys?
Metals and some non-metals mixed together
What are the properties of stainless steel and what elements is it made up of?
- Strong & resists corrosion
- Iron & Chromium
What are the properties of Duralumin and what elements is it made up of?
- Strong & low density
- Aluminium, copper & magnesium
What elements do plants need?
Nitrogen, Potassium & Phosphorus
What are the 2 types of fertilisers?
Natural & synthetic
What are examples of natural fertilisers?
Compost or manure
What are synthetic fertilisers?
Ionic compounds that contain either N, P or K
What property does a good fertiliser have and why?
- Soluble in water
- So it can be absorbed through the roots
What is ammonia and is it soluble?
A colourless gas with a pungent smell.
Yes.
What solution does ammonia give?
An alkaline solution
What is the Haber process and when was it developed?
It converts nitrogen and hydrogen gas into ammonia.
Early 20th century.
What is the Ostwald process?
The production of nitric acid by catalytic oxidation of ammonia
What is the catalyst used in the Ostwald process?
Platinum
Why do atoms become radioactive?
Because their nuclei are unstable
What happens when an atoms nucleus becomes unstable?
It will begin to decompose to release energy and particles
What are the three types of radiation?
Alpha, beta, gamma
What are uses for radiation?
Radioisotopes have a range of uses in medicine and in industry
What is Americium 241 used for?
Put in smoke detectors
What is Iodine 131 used for?
To treat thyroid cancer
What is the half-life of an atom?
The time taken for the number of radioactive atoms in a substance to drop by half
What happens when metals react with air?
They become metal oxides
What happens when metals react with water?
They undergo a displacement reaction
What is the equation for displacement reactions?
Metal + Water -> Alkali + Hydrogen
What happens when metals react with acid?
Hydrogen gas is displaced and a salt solution is formed
What is the reactivity series?
Lithium
Potassium
Barium
Calcium
Sodium
Magnesium
Aluminium
Carbon
Zinc
Iron
Nickel
Tin
Lead
Hydrogen
Copper
Mercury
Siver
Gold
Platinum
From what element to what element reacts with oxygen?
Lithium -> Silver
From what element to what element reacts with dilute acid?
Lithium -> Lead
From what element to what element reacts with water?
Lithium -> sodium
What are oxidation reactions?
Reactions that always involve the loss of electrons
What are reduction reactions?
Reactions that always involve the gain in electrons
What is corrosion?
The breakdown of a metal by chemical reactions with its environment
What must be present for corrosion to take place?
Oxygen and water
What happens when metals corrode?
They become weak and dull
What methods do we use to protect metals from corrosion?
- Physical barriers
- Electrochemical protection
- Galvanising
What are examples of physical barriers when protecting metals from corrosion?
Paint, oil, plastic or a less reactive metal
What does electrochemical protection involve when protecting metals from corrosion?
Giving the metal electrons to stop it corroding
What does galvanising involve when protecting metals from corrosion and why?
Coating the metal with zinc.
Zinc has a natural oxide layer which stops it corroding.
What reaction is extracting metals an example of?
A reduction reaction
What are the methods of extraction for the elements in the reactivity series?
What do chemical cells do?
Convert chemical energy to electrical energy
What is a battery?
2 or more chemical cells joined together
What does a simple chemical cell consist of?
2 electrodes made of different metals and an electrolyte
What is an electrolyte?
A solution/material that can conduct electricity
Why are electrolytes important?
To complete a circuit
What is an ion/salt bridge used for and what does it do?
Link 2 cells together, complete a circuit
