Topic 5- Transition metals + alloys Flashcards
What are most metals?
Transition metals
Transition metals have high…
-Bioling point
-Density
Do transition metal form coloured compounds?
-Yes
What are transition metals good for?
-Catylists
-E.g iron in haber process
What does the broad range of transition metals mean?
-Many different ionic charges
What is the haber process?
Nitrogen + Hydrogen —> Ammonia
For plant fertiliser, grows all food
What temp + pressure is the reaction vessel?
-450 degrees
-200 atm
-Iron catalyst helps
What type of reaction is the haber reaction and what does this mean we need to do?
-Reversable
-Seperate ammonia from H and N atoms
-Ammonia has higher boiling point so we condense it
What is rust and how is it made?
Metal + oxygen + water
How does rust corrode metals?
-Surface layer rusts
-Rust layer flakes off
-This repeats
What is corrsion?
Destruction of metals by chemical reactions
What does oxidation of metals cuase?
Rusting
How can rusting of metals be prevented x3?
-Excluding oxygen
-Exclusion of water
-Sacrificial protection
How can we exclude oxygen + water from metal to prevent rust?
-Paint
-Coat with plastic
-Coat with oil or grease
-Alluminium has an oxide coat so protected from further oxidation + water
How can we exclude water only to prevent metal rust?
-Use a desiccant (absorbs water)
-E.g calcium carbonate
How can we exclude oxygen only to prevent metal rust?
-Place in a vacuum
How can we use sacrificial protection?
-Galvanise/coat metal with another
-Less reactive metal
-Wont rust
e.g zinc galvanises iron
What can electroplating be used for?
-Improve appearence + strength of metal
plate metal with another
How does electroplating strengthen metals?
-Acts as a barrier to prevent rust
How does electroplating improve appearence?
-Plate with less reactive metal to prevent rust
-Cheaper, plate with gold
How is electroplating done?
-Electrolysis
-Cathode is metal to be plated
-Solution + anode is metal to plate
solution + anode ions r attracted to cathode
What is an alloy?
-Mxture of 2 or more elements
-Atleast one is a metal
Why are alloys used to strengthen materials
- Metals such as gold, aluminium and iron are too soft
- In a pure metal all atoms are unifrom meaning they can slide over eachother
- Adding different element disrupts uniform atoms + no longer as maluable
What and why is iron alloyed into?
-Steel
-Mix of carbon + iron + more
-Makes it stronger
What are the 3 examples of iron alloyes?
-Low-carbon steel
-High-carbon steel
-Stainless steel
What is low-carbon steel used for?
-Soft + maluable
-Used for sheeting
What is high-carbon steel used for?
-Strong + hard
-Cutting
What is stainless steel a mix of and what is it used for?
- Iron, carbon, nickel + chromium
-Resistant to corrosion
-Used in cutlery
What is alluminium used for and why?
-Low density
-Maluable
-resistant to rust due to oxide layer
-Used in wrapping food (unreactive to food) and aicrafts
What is gold used for and why?
-Good resistance to corrosion as unreactive
-zinc can be added for extra strength + cheaper
-Jewlery
What is copper used for and why?
-Good conductor
-Resists errosion
-Electrical cables
What is aluminium alloyed with magesium used for?
-Magnalium
-Low density + strong + high corrosion resistance
-Cars + planes
What is Copper alloyed with zinc used for?
-Brass
-Hard + resistant to corrosion
-Not as good a conductor as copper
-Used in coins
-Used in pins for electrical plugs
What is gold + zinc alloy?
-Jewellery gold
-Cheaper + stronger
