How do properties of metals compare with those of alkali metals?
- Harder and stronger (cannot be cut with knife)
- More dense
- Higher melting and boiling points (except mercury)
- Much less reactive
What is the colour of the metal compound iron (II) oxide (FeO₂)?
Black.
What is the colour of the metal compound iron (III) oxide (Fe₂O₃)?
Red/brown.
What is the colour of the metal compound copper (II) sulfate crystals?
Blue. Can be turned white by heating crystals to remove water.
What is the use of coloured compounds of transition metals?
- Colour stained glass windows
- Colour paints and dyes
- Coloured glazes on pottery
What is a pigment?
A water insoluble transition metal compound used to make paints.
Which compound forms a blue pigment?
Cobalt compound.
Which compound forms a white pigment?
Titanium compound.
Which compound forms a yellow pigment?
Chromium compound.
What is a dye?
A water soluble coloured compound (usually transition metal compound) which forms a chemical bond with fabric.
What is a mordant?
A chemical that binds dye to a fabric.
What are environmental considerations for the use of pigments and dyes?
- Both coal or oil-based so raw material is non-renewable
- Some made using carcinogenic substances
- Most are harmful to the environment
What are the environmental solutions to using dyes and pigments?
Renewable biomass (such as sugar, straw or wood) could be the raw material for making artificial dyes in the future.
What are the properties of alkali metals?
- Soft (can be cut by knife), softness increases going down group
- Low density
- Low melting/boiling points
- Good conductors of heat and electricity
- Shiny (seen when freshly cut, quickly tarnish due to reaction with oxygen)
How can we prevent rusting?
- Exclude air/oxygen (paint, oil/grease, coating with plastic)
- Exclude water (desiccator to absorb water)
- Sacrificial protection or galvanizing (coating with zinc)
What is sacrificial protection?
Protection of iron or steel against corrosion by using a more reactive metal. Pieces of zinc or magnesium alloy are attached to pump bodies and pipes. The protected metal becomes the cathode and does not corrode.
What are the uses of aluminium and what are its relevant properties?
Uses: airplanes, cars, bicycles, trains, trucks, ladders, window frames, door frames
Relevant properties:
- Low density
- Strong
- Resistant to corrosion
What are the uses of copper and what are its relevant properties?
Uses: electrical wires/cables
Relevant properties:
- Good conductor of electricity
Uses: water pipes, roofing, coins, jewellery, statues, musical instruments
Relevant properties:
- Resistant to corrosion
What are the uses of gold and what are its relevant properties?
Uses: jewellery, coins, dentistry
Relevant properties:
- Excellent resistance to corrosion
- Valuable
- Low strength
Uses: electronic devices, circuit boards, switch contacts
Relevant properties:
- Excellent conductor of electricity
What are the uses of silver and what are its relevant properties?
Uses: jewellery, cutlery, coins
Relevant properties:
- Very good resistance to corrosion
- Valuable
- Low strength
Uses: electronic devices, circuit boards, switch contacts
Relevant properties:
- Excellent conductor of electricity
What is an alloy?
A mixture of metals.
How are alloys different than pure metals?
- Contain some atoms of other elements that are different sizes
- This disrupts the layered structure and stops layers sliding over each other
- This makes alloys stronger and harder
Which alloy is iron made into to prevent rusting?
Stainless steel (contains small amounts of chromium and nickel and does not rust).
