SC11 Flashcards
(18 cards)
What are the observations of lithium in water?
- Floats on surface
- Gently fizzes
- Gradually reacts and disappears
- Forms colourless solution
What are the observations of sodium in water?
- Floats on surface
- Melts almost at once
- Forms small silvery ball that dashes around surface
- White trail of sodium hydroxide which dissolves to give colourless solution
- If sodium becomes trapped on side of container, hydrogen may catch fire to burn with an orange flame
What are the observations of potassium in water?
- Floats on surface
- Forms small silvery ball that dashes around surface
- Coloured lilac flame
What are the observations of rubidium in water?
- Sinks
- Reacts violently and immediately
- Spitting
What are the observations of caesium in water?
- Explodes on contact
What are uncombined elements?
A few metals found on Earth that are unreactive (such as gold and platinum).
What is an ore?
A rock containing compounds from which a metal can be extracted for profit.
What is extraction?
The process of getting a metal from a compound in a rock by a chemical reaction.
How are low reactivity metals extracted?
Heating the ore with carbon.
How are high reactivity metals extracted?
Electrolysis of a molten compound.
What is bioleaching?
An extraction method that uses bacteria grown on a low grade ore. The bacteria produces a solution containing copper ions (leachate). Copper is extracted from the leachate by displacement using scrap iron, then purified by electrolysis. Can be used for metals such as nickel, cobalt and zinc.
What is phytoextraction?
An extraction method that involves growing plants that absorb metal compounds. The plants are burnt to form ash, from which the metal is extracted.
What are the advantages and disadvantages of bioleaching?
Advantages:
- No harmful gases are produced
- Causes less damage to landscape than mining
- Conserves supplies of higher grade ores
- Does not require high temperatures
Disadvantages:
- Very slow
- Toxic substances and sulfuric acid can be produced by the process and damage the environment
What are the advantages and disadvantages of phytoextraction?
Advantages:
- No harmful gases are produced
- Causes less damage to landscape than mining
- Conserves supplies of higher grade ores
- Can extract metals from contaminated soils
Disadvantages:
- Very slow
- More expensive than mining some ores
- Growing plants is dependent on weather conditions
What happens when aluminium comes in contact with oxygen?
It does not corrode as much as expected because its surface oxidises quickly to form a protective layer of aluminium oxide which stops any further corrosion.
What are the advantages of recycling metals?
- Metal ores will last longer
- Less energy is needed to recycle them than is needed to extract them from their ores
- Less damage to landscape than mining
- Lower carbon dioxide emissions due to less mining
- Reduces waste metals going to landfill sites
What are the disadvantages of recycling metals?
- Cost and energy used in collecting, sorting and transporting metals to be recycled
- May use more energy
- May be more expensive for some metals
What are the stages of recycling metals?
- Collecting the metals
- Separation from other metals
- Some metals are separated by hand
- Iron and steel are separated from others using a magnet because they are
magnetic - Melting down old metals and remoulding them
- Metals obtained from waste are melted down to form blocks and sold on
to manufacturers
