Topic 5- Separate Chemistry Flashcards
Where are transition metals found on the periodic table ?
The transition metals are found in the middle of the periodic table. To their left is Group 2 and to their right is Group 3
Relative to the alkali metals, what do transition metals have ?
Higher density
Higher melting points
Lower reactivity
Greater strength and hardness
Why are transition metals useful in construction?
The high density makes transition metals useful in construction
Why are transition metals good for cooking equipment ?
High melting points make transition metals useful for cooking equipment.
What are the special properties of transition metals ?
Can form ions with different positive charges - Iron: Fe2+ and Fe3+.Copper: Cu+, Cu2+.
Can form different colour compounds - Copper(I) sulfate is white; copper(II) sulfate is blue.
Often used as catalysts
What colour is copper (I) sulfate ?
white
What colour is copper(II) sulfate ?
blue
What is the catalyst used in the Haber process, which results in the production of ammonia ?
Iron (Fe)
What are used in catalytic converters in cars ?
Platinum (Pt) and rhodium (Rh)
What proves that transition metals are generally much less reactive than alkali metals ?
Iron takes weeks to rust when it comes into contact with oxygen and water. Sodium, however, rusts in a few seconds.
What is corrosion ?
describes the gradual destruction of metals because of chemical reactions between metals and the oxygen and water around them
What is the word equation for the rusting of iron ?
Iron + oxygen + water → hydrated iron(III) oxide.
What is the experiment for rusting ?
Take a boiling tube and put an iron nail inside under three different sets of conditions and see if it rusts:
Only water - no rust.
Only air - no rust.
Air and water - rust.
What are metals reacting with in the environment when they corrode?
Oxygen and water
What are the 3 methods to prevent corrosion?
Coatings
Sacrificial method
Galvanisation
How does coating work ?
applying a coating that acts as a barrier, such as greasing, painting or electroplating
What’s an example of coating to prevent corrosion ?
Aluminium has an oxide coating that protects the metal from further corrosion by preventing the metal’s surface coming into contact with oxygen and water.
What’s a disadvantage of the coating method to prevent corrosion?
A disadvantage is that any damage to the coating will lead to the metal becoming exposed and so corrosion will take place.
How does the sacrificial method work ?
a metal that requires protection will have a more reactive metal attached to it.
This means that water and oxygen will stop reacting with the protected metal as they are too busy reacting with the sacrificial metal!
What is galvanisation ?
Galvanising is a hybrid of coatings and the sacrificial method.
The metal that needs protecting is sprayed with a more reactive metal. This initially acts as a coating.
If the more reactive metal is damaged, it will continue to protect as a sacrificial metal.
What is electroplating used for ?
We can use this process to coat a cheaper metal with a more expensive one. This gives the cheaper metal the appearance of the more expensive metal, which could be gold or silver.
This gives us the option of buying cheaper jewellery.
How does electroplating jewellery work ?
The process works by placing the metal to be electroplated at the negative electrode (cathode) and the coating metal at the positive electrode (anode).
Metals are good conductors of electricity. This is why we use copper, steel (alloy of iron) and aluminium for electrical cables.
The cables are surrounded by an insulator (does not conduct electricity), such as plastic for safety.
What process is used for electroplating ?
Electrolysis.
What do we use electroplating for?
Coating cheaper metals with more expensive ones
What’s an alloy ?
An alloy is a combination of 2+ elements, where at least 1 is a metal.
What makes it harder for the layers to slide across each other when a force is applied to an alloy ?
The ions of the different elements are different sizes.
Why are alloys stronger than pure metals ?
The ions of the different elements are different sizes.
This makes it harder for the layers to slide across each other when a force is applied to the alloy.
What are alloys commonly used for ?
Construction.
What are the metal alloys used in everyday life ?
Steel(iron) Gold Aluminium Bronze Brass
What are steels ?
alloys of iron that contain carbon as well as other metals
Are high carbon steels strong ?
Are high carbon steels brittle ?
What are high carbon steels used to make ?
strong
brittle
Making cutting tools and blades
Are low carbon steels soft ?
Are low carbon steels malleable ?
What are low carbon steels used for ?
soft
Malleable
making car bodies.
What are in stainless steels ?
Stainless steels (steels containing chromium and nickel)
What are the properties of stainless steels ?
are strong and resistant to corrosion
What are stainless steels used for ?
Uses include cooking utensils and cutlery.
Why do jewellers often add metals such as silver, copper and zinc to gold ?
Pure gold is soft
And these metals are added to produce a more resilient substance.
What do Carats provide a measure of ?
purity of a gold alloy
24 carats = 100% gold
So, 12 carats = 50% gold
What is the key feature of aluminium alloys ?
low density
What is aluminium used for ?
manufacturing planes and armour plating for military vehicles.
What is bronze an alloy of ?
copper and tin.
If you add gin to bronze what will happen ?
increases the hardness of the material
What is bronze used to make ?
making coins
electrical hardware
statues
What is brass an alloy of ?
copper and zinc.
If you add zinc to brass what will happen ?
makes the material more malleable (easy to bend).
What are the uses for brass ?
hinges
locks
plumbing
plug sockets.
