C2c Flashcards
How can copper be extracted from its ore?
Copper is dug out of the ground as a copper ore. Then the metal is extracted from it by mixing the ore with carbon and heating. The copper you get this way isn’t pure enough to use in electrical conductors (the purer it is, the better it conducts). But it can be purified using electrolysis.
What is reduction?
The removal of oxygen from a substance.
What can copper be purified by?
Electrolysis.
Why is recycling copper cheaper than extracting copper from its ore?
Recycling copper uses only 15% of the energy that’d be used to mine and extract the same amount, so it saves resources and energy.
What is the apparatus needed to purify copper by electrolysis?
- The cathode is the negative electrode. It starts as a thin piece of pure copper and more pure copper adds to it. Pure copper is deposited on the pure cathode.
- The anode is the positive electrode. It’s just a big lump of impure copper, which will dissolve. Copper dissolves from the impure anode.
- Copper(II) Sulfate Solution
- Electrical Supply
What are some of the advantages and disadvantages of recycling copper?
It’s cheaper to recycle copper than it is to mine and extract new copper from its ore.
But it can be hard to convince people that it’s worth the effort to sort and recycle their metal waste. Even then you have to sort out the copper from all the other waste material - which takes time and energy.
What is the use of electrolysis in the purification of copper?
Impure copper is the anode and the electrical supply pulls electrons off copper atoms at the anode, causing them to go into solution as Cu2+ ions.
Pure copper as cathode. The electrical supply offers electrons at the cathode to nearby Cu2+ ions to turn them back into copper atoms.
Copper(II) Sulfate solution as electrolyte containing Cu2+. Electrolytes are usually free ions dissolved in water.
Cathode gains mass because copper is deposited at the cathode.
Anode loses mass as copper dissolves away from the anode.
Why does the electrolytic purification of copper involve both oxidation and reduction?
The reaction at the cathode is Cu2+ + 2e- = Cu
Reduction is the gain of electrons so this is an example of a reduction reaction.
The reaction at the anode is Cu = Cu2+ + 2e-
Oxidation is the loss of electrons so this is an example of an oxidation reaction.
What are alloys?
Mixtures containing one or more metal elements.
What are examples of alloys?
Brass, bronze, solder, steel and amalgam.
What is one important large scale use for each alloy?
Amalgam - tooth fillings
Brass - musical instruments, coins and door decorations e.g. door knockers
Solder - to join electrical wire
What are the main metals in amalgam, brass and solder?
Amalgam - mercury
Brass - copper and zinc
Solder - lead and tin
What are the properties of an alloys different from?
The properties of the metals from which it is made.
What are the properties needed by brass for its uses?
Most of the properties of brass are just a mixture of those of the copper and zinc, although brass is harder than either of them.
What are the properties needed by solder for its uses?
Unlike pure materials it doesn’t have a definite melting point, but gradually solidifies as it cools down. This is pretty useful if you want to solder things together.
What are the properties needed by steel for its uses.
Steel is an alloy of iron and carbon. Steel is harder than iron and stronger, as long as the amount of carbon is not too much. Iron on its own will rust quickly, but steel is much less likely to rust. This is good for girders, bridges, engine parts, cars and cutlery.
How has the use of ‘smart alloys’ such as those with a shape memory property increased the number of applications of alloys?
Nitinol is the name given to a family of alloys of nickel and titanium that have shape memory. This means they “remember” their original shape, and go back to it even after being bent and twisted. This has increased the number of uses for alloys. You can get specs with Nitinol frames - these can be bent and even sat on and they still go back into their original shape.
