Most metals have many physical properties in common. For example, they are shiny silvery-grey solids with high melting points and boiling points, high density, good conductors of heat and electricity, malleable (easily bent or beaten into any shape) and ductile (strong enough to be drawn into wire). Metals may or may not react with oxygen, water or acid. They also vary in 'market value', in other words, their material worth.
In task 1 you will describe which particular physical properties explain a particular use of a given metal. Task 2 looks at how some simple chemical reactions of metals or their compounds are very useful.
- Open Yenka Model 1.
- Look at the metals on display – only two metals are not 'silvery' in colour. Which are they? Give at least two reasons why are they used for jewellery.
AnswerGold and copper.
They are easily shaped (cut or bent); do not corrode easily (gold not at all, copper slowly); gold is scarce, giving it extra status and value; they are relatively strong without being brittle; their attractive 'different colour' adds to their status too.
- Iron is used to make cooking pots.
(a) Give at least three reasons why it is such a good structural material for cooking pots.
(b) Using aluminium for cooking pans is not considered desirable these days. Why not?Answer(a) Strong, malleable, good conductor of heat, high melting point.
(b) Aluminium has in many ways similar properties to iron, but it reacts with acidic foods like fruit juices and aluminium is a poisonous metal.
- Copper and silver can both be used in electrical wiring.
(a) Which properties make them good metals to use for electrical wiring?
(b) Why is copper more likely to be used than silver?Answer(a) Strong enough to be drawn out into wire (won't snap easily); very good conductors of electricity
(b) Silver is too costly.
The typical physical properties of metals: they are usually shiny silvery-grey solids with high melting points and boiling points, high density, good conductors of heat and electricity, malleable (easily bent or beaten into any shape) and ductile (strong enough to be drawn into wire).
This means they can be used in a wide variety of situations as structural materials, though some may be too costly for widespread use.
Metals show a wide variation of reactivity towards oxygen, water or acid. The relative reactivity may be an advantage or disadvantage depending on the situation.
- Open Yenka file Model 2.
- Just as different metals have different reactions with water and oxygen, they also have different reactions with acids. Add each metal to the beaker of acid beside it and observe what happens.
- Open the Yenka file Model 3. For each of the following metals – gold, sodium, magnesium and zinc – investigate how they react with both cold water and steam, taking note of your observations. In each case:
(i) Add 2 g of the metal to the cold water (except for sodium which can only be added as a lump).
(ii) Turn on the first heater until steam is produced in the flask of water, then add 2 g of the metal to the second flask and turn on the heater beneath it.
You will need to reload the model (by pressing F5) for each metal.AnswerGold: no reaction in cold water or steam.
Sodium: reacts violently in water to form hydrogen and sodium hydroxide; reacts with steam to form hydrogen and sodium oxide.
Magnesium: reacts in cold water to form hydrogen and madnesium oxide, no reaction with steam.
Zinc: reacts in cold water to form zinc hydroxide, no reaction with steam.
- Dilute hydrochloric acid or dilute sulfuric acid can be used to clean corroded (oxidised) metal surfaces such as iron or steel. Two general reactions can take place. Complete the general equations followed by some of the specific reactions possible.
(a) Metal + acid → ________ + ________
(b) Metal oxide + acid → ________+ ________
(c) Iron + hydrochloric acid → ______________ + ________
(d) Iron oxide + sulfuric acid → ______________+ ________
(e) Fe (s) + H2SO4 (aq) → ________ + ________Answer(a) metal + acid → salt + hydrogen
(b) metal oxide + acid → salt + water
(c) iron + hydrochloric acid → iron chloride + hydrogen
(d) iron oxide + sulfuric acid → iron sulfate + water
(e) Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)
Three very useful reactions of metals or their compounds are:
(1) Metal + acid → salt + hydrogen
(2) Metal oxide/hydroxide + acid → salt + water
(3) Metal carbonate/hydrogencarbonate → salt + water + carbon dioxide
Hydrochloric acid makes chloride salts, sulfuric acid makes sulfate salts and nitric acid makes nitrate salts.