Chapter 13 - The Behaviour of Metals Flashcards
8 physical properties of metals
- strong
- malleable
- ductile
- sonorous
- shiny when polished
- good conductors of electricity and heat
- high melting and boiling points
- high density
Formula for density
mass (grams)
density = ———————
volume (cm^3)
4 Chemical properties of metals
- React with oxygen to form OXIDES
- Metal oxides are BASES (neutralise acids, forming salt and water)
- Metals form positive ions when they react
- For the metals in the numbered groups, the charge on the ion is the same as the group number. But transition elements have variable valency
What is VARIABLE VALENCY?
When elements can form ions with different charges e.g Cu+ / Cu2+
Specific properties of iron and its uses
Iron is malleable and strong Rusts easily in damp air Unlike most other metals it's magnetic It melts at 1530 degrees c. - used for gates
Specific properties of sodium
- soft (can cut with a knife)
- floats on water and reacts with it immediately forming a solution
- melts at 98 degrees C
Specific properties of gold and its uses
- unreactive
- malleable, ductile, looks attractive
- quite rare
- melts at 1064 degrees C
- used for jewellery and precious objects
What does reactive mean?
A reactive element has a strong drive to become a compound so that its atoms gain stable outer shells.
Reaction between sodium and water
What’s formed?
Sodium reacts violently with cold water, whizzing over the surface.
Hydrogen gas and a clear solution of sodium hydroxide are formed
Reaction between calcium and water
What’s formed?
The reaction between calcium and cold water is slower.
Hydrogen bubbles off, and a cloudy solution of calcium hydroxide Ca(OH)2 forms.
Reaction between magnesium and water
What’s formed?
Magnesium reacts very slowly with cold water, but vigorously on heating in steam, it glows brightly.
Hydrogen and solid magnesium oxide MgO form.
Potassium reaction with water
Products
Very violent with cold water catches fire
Hydrogen and a solution of potassium hydroxide, KOH
Zinc reaction with water
Products
Quite slow with steam
Hydrogen and solid zinc oxide ZnO
Iron reaction with water
Products
Slow with steam
Hydrogen and solid iron oxide Fe3O4
Copper, silver, gold reaction with water
Products
no reaction
What is the pattern for the products formed when metals react with water
First 3 produce hydroxides and the rest produce insoluble oxides, if they react at all
magnesium reaction with hydrochloric acid
Products
Vigorous
Hydrogen and a solution of magnesium chloride MgCl2
zinc reaction with hydrochloric acid
Products
quite slow
hydrogen and a solution of zinc chloride ZnCl2
iron reaction with hydrochloric acid
Products
slow
hydrogen and a solution of iron(II) chloride FeCl2
lead reaction with hydrochloric acid
Products
slow, and only if the acid is concentrated
hydrogen and a solution of lead (II) chloride PbCl2
Copper, silver, gold reaction with hydrochloric acid
Products
no reaction, even with concentrated acid
Chemical equation between magnesium and hydrochloric acid
Mg (s) + 2HCl (aq) —> MgCl2 (aq) H2 (g)
What happens during a reaction between a metal and water/hydrochloric acid?
When a metal does react with H2O or HCl, it drives hydrogen out (displaces it) and takes its place. This shows that. the metal is more reactive than hydrogen and has a stronger drive to form a compound.
Is the displacement of hydrogen a redox reaction?
Yes
general explanation of redox reaction between magnesium and hydrochloric acid
When magnesium reacts with hydrochloric acid, its atoms lose electrons (is oxidised). The hydrogen ions from the acid gain electrons (are reduced).
The half equations for the reaction between magnesium and hydrochloric acid
Mg –> Mg2+ + 2e- (oxidation)
2H+ + 2e- –> H2 (reduction)
How is the reactivity series ordered?
Metals are put in order based on their reactivity with water and hydrochloric acid
What happens when MgO is mixed with powdered carbon and heated?
What does this mean?
There’s no reaction
This means magnesium is more reactive than carbon