The Downs School ICT Home by nikeborome

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									       1. Physical properties of metals and non-metals

In the table below is a clear summery of the general physical properties of metals and non-metals. You
need to know these properties for your exam.

Physical               Metals                                Non-metals
properties
Electrical             Good conductor                        Poor conductor, act as an insulator
conductivity           (copper wires)                        (graphite is an exception)
Heat conduction        Good                                  Poor, act as an insulator e.g. rubber
                       (Iron cooking pans)
Sound when hit         Rings                                 Often dull
                       (wind chimes and church bells)
Lustre                 Shiny                                 Dull
(shininess)            (silver and gold jewellery and        (graphite in pencils)
                       coins)
Malleability           Easily bent                           Brittle
(ability to be bent)   (copper water pipes, aluminium        (diamonds shatter when hit hard. Graphite
                       cooking foil)                         snaps in pencils)
State                  Most are solids                       Most are gases, some are solid
Density                High                                  Low
                       (lead plumb line, gold bars)          (carbon fibre in fishing rods)
Magnetic               Only three metals                     None
(attracted to a        (nickel, cobalt and iron)
magnet)

Reactivity series of metals

This is a list of metals (and often the non-metals carbon and hydrogen) in order of their chemical
reactivity. The most reactive is at the top and the least is at the bottom.

Element                    Symbol
Potassium                  K             Most reactive *Aluminium seems unreactive in water and acidic
Sodium                     Na                          solutions because it has a thin, tough layer of
                                                       aluminium oxide on its surface.
Calcium                    Ca
Magnesium                  Mg                           **Two non-metals are in this series. This helps you
*Aluminium                 Al                           to understand the making of metals by reduction
                                                        using carbon and how metals react with acids and
**Carbon                   C                            water.
Zinc                       Zn
Iron                       Fe
Lead                       Pb
**Hydrogen                 H
Copper                     Cu
Silver                     Ag
Gold                       Au            Least
                                         reactive




Metals reaction with oxygen
Metals react with the oxygen in air, forming oxides. This can often be made clearer by reacting the
metal with pure oxygen. Below are some word equations. There is a description with the first example.

magnesium + oxygen  magnesium oxide

Here magnesium metal has reacted with the oxygen in the air and has been oxidised. This means that
oxygen has joined to the magnesium making a compound from the elements. The compound is called
magnesium oxide. In general, metal + oxygen  metal oxide. Use this description to help you through
the equations below.

zinc + oxygen  zinc oxide

copper + oxygen  copper oxide

calcium + oxygen  calcium oxide

There are a few metals that do not react with oxygen in the air. They include the very unreactive
metals gold, platinum and silver.

Metals reacting with water

Metals above hydrogen in the reactivity series will react with water. The metals below hydrogen - like
copper, silver and gold - do not react with water or steam.

Lithium, sodium, and potassium all react well (fast, vigorously) with cold water. These metals react and
dissolve, producing an alkaline solution. This is a metal hydroxide solution. This turns Universal
Indicator purple. While reacting, hydrogen (which is a flammable gas) is given off. You can hear it
being made by the fizzing noise.

lithium + water  lithium hydroxide + hydrogen

potassium + water  potassium hydroxide + hydrogen

sodium + water  sodium hydroxide + hydrogen

Magnesium is less reactive than these three. Therefore it only reacts slowly with cold water. It will
react vigorously with steam. The products are slightly different as the oxide is formed.




Once the magnesium has become very hot it starts to react with the steam in a very exothermic
reaction. The magnesium, which was silver in colour, becomes pure white and a flammable gas -
hydrogen - is formed. This is set on fire.
Metals reacting with acids


        Metals (above hydrogen in the reactivity series) react with dilute acids.
        The reaction involves:

             1. The metal dissolving
             2. Fizzing as hydrogen gas is being formed.
             3. The test tube gets warm because the reaction produces thermal energy - i.e. it is
                exothermic.

        The general word equation is:

        acid + metal        hydrogen gas + a salt

        A salt is a compound made from an acid when a metal has replaced the hydrogen. The table
         below gives you the names of the salts formed when using each acid.

                                  Acid                 Name of salt (and an example)
                   Hydrochloric acid                   Chlorides
                                                       (e.g. Sodium chloride)
                   Nitric Acid                         Nitrates
                                                       (e.g. Calcium nitrate)
                   Sulphuric acid                      Sulphates
                                                       (e.g. Magnesium sulphate)

Examples

zinc + sulphuric acid  zinc sulphate + hydrogen
nitric acid + magnesium  magnesium nitrate + hydrogen
calcium + hydrochloric acid  calcium chloride + hydrogen

The chemical test for hydrogen gas
Take a lighted splint or spill and place it in the gas. If there is a squeaky pop - and often the splint or
spill is blown out - then the gas is hydrogen.


magnesium + water (steam)  magnesium oxide + hydrogen

Displacement reactions

A displacement reaction happens between a reactive metal and a solution of a less reactive metal
compound. The more reactive metal will displace the less reactive metal from its compound in
solution.

What do you often observe (see, hear, feel) in this type of reaction?

    1. The more reactive metal will dissolve.
    2. The less reactive metal will appear at the bottom of the tube or plate on the more reactive
       metal.
    3. The solution may change colour.
    4. The reactions are exothermic, so the tube gets warm.
Examples of displacement reactions

copper sulphate solution + magnesium         magnesium sulphate solution + copper




               iron + copper sulphate solution      iron sulphate solution + copper
Obtaining a reactivity series from displacement reactions

The following metals are placed in the solutions shown. If a reaction takes place then an X is placed in
the box.

From the results you can tell which metal displaces another metal from its compound in solution.
Therefore the metal doing the displacing is more reactive.

                      Copper               Silver          Magnesium         Zinc              Lead
Copper nitrate
                                                                  X           X                 X
solution
Silver nitrate
                         X                                        X           X                 X
solution
Magnesium
nitrate solution
Zinc nitrate
                                                                  X
solution
Lead nitrate
                                                                  X           X
solution

From the results above you can work out the reactivity series, follow the working out below.

Most reactive metal is Magnesium(4 ticks)

Zinc (3 ticks)

Lead (2 ticks)

Copper(1 tick)

Least reactive metal is Silver (0 ticks)

NAME OF NON-        COMPOUND MADE                   ADD NON-METAL OXIDE TO           FORMULA OF
METAL               WHEN BURNT IN                   WATER – NAME OF ACID             ACID
                    OXYGEN                          FORMED
Sulphur             Sulphur dioxide                 Sulphuric acid                   H2SO4
Nitrogen            Nitrogen dioxide                Nitric acid                      HNO3
Wise up words


    1.    Physical properties (melting and boiling point, density, state)
    2.    Chemical properties (the substances chemical reactivity, the reactions it undergoes)
    3.    Displacement (One metal pushes another metal from its compound into solution)
    4.    Reactivity series (a list of metals in order of their chemical reactivity)
    5.    Salt (a compound formed from an acid where the hydrogen has been replaced by a metal
Non typical metals and non-metal elements



Mercury is a metal and it is a liquid at room temperature. The bonding
between the atoms of mercury is not as strong as in most metals. It is
therefore a liquid at room temperature as there is enough thermal energy to
allow the bonds to be broken. This gives the mercury atoms enough kinetic
energy to allow them to move position.




Diamond is a form of carbon and is a non-metal element.



                          Most non-metals are gases or low melting point solids, but diamond is a
                          high melting point solid. It is also a very hard substance. These properties
                          are due to the extensive and strong bonding between the carbon atoms in
                          diamond.




The bonds are arranged in three dimensions between the carbon atoms. These bonds are strong.

Graphite is another form of carbon (another allotrope of carbon). It is a non-typical, non-metal element,
because it conducts electricity. The layers of carbon atoms have free mobile electrons between them.
These allow graphite to conduct electricity.

Metals reacting with oxygen
Metals will react with oxygen in air or pure oxygen to form oxides. The metals are oxidised. The
reactions below show this process. Two elements are reacting together to form a single new
compound which is an oxide.

Here the magnesium atoms are reacting with oxygen molecules (an oxidation reaction) to make the
compound magnesium oxide.

                                        2Mg + O2          2MgO

Likewise copper atoms are bonding or joining to oxygen atoms from the oxygen molecule in this
oxidation reaction. The new substance formed is the compound copper oxide.

                                        O2 + 2Cu          2CuO
In general:

                                   metal + oxygen         metal oxide

Some notable exceptions are silver and gold, which do not react with oxygen.




Metals reacting with water
Lithium, sodium, and potassium all react (fast and vigorously) with cold water. These metals react and
dissolve, producing an alkaline solution of pH 11 to 13. During this reaction hydrogen, a flammable
gas, is given off. You can hear it being produced by the fizzing noise.

In the first example below, you would see a silvery piece of potassium metal floating on the water. It
would be on fire, as the hydrogen gas produced will burn with a purple flame. Soon, the metal will
have all reacted and dissolved, making the water alkaline and all the fizzing will have ceased.


                      potassium + water          hydrogen + potassium hydroxide

                           2K + 2H2O                         H2 + 2KOH


Magnesium is less reactive than the above three. It only reacts slowly with cold water. It will, however,
react vigorously with steam. The products are slightly different as the oxide is formed.




                                       Mg + H2O(g)        MgO + H2

Metals reacting with acids
All acids are compounds of hydrogen. It is this hydrogen that is displaced by the metal when it reacts
with an acid. Only metals above hydrogen in the reactivity series can cause this displacement, so only
metals above hydrogen in the reactivity series react with dilute acids. Therefore you always get
hydrogen gas as a product in this type of reaction. The metal dissolves and forms a salt as the other
product in the reaction.

The general word equation is:

                                acid + metal         hydrogen gas + salt

The reaction involves the following observations:

    1.   The metal dissolving
    2.   Fizzing as hydrogen gas is formed.
    3.   The test tube gets hot as an exothermic reaction is taking place.
    4.   After the reaction has finished the solution becomes clear.

Examples:
   zinc + sulphuric acid                  zinc sulphate + hydrogen
         Zn + H2SO4                              ZnSO4 + H2



sulphuric acid + magnesium            hydrogen + magnesium sulphate

         H2SO4 + Mg                              H2 + MgSO4
Special Note: the chemical test for hydrogen gas. Take a lighted splint or spill and place it in the gas.
If there is a squeaky pop, then the gas was hydrogen.
Metals, acids and reactivity

To work out the order of reactivity of these four metals (Ca, Cu, Zn & Mg) place pieces of each metal
into dilute hydrochloric acid. Now look at the tubes. Which tube (metal) is reacting the most quickly?
Now which one is not reacting? Put the other two tubes (metals) in the correct order. Now make a
reactivity series list. Most reactive metal at the top.




From the observations above it is clear that the order of reactivity is


                                        Ca    Most reactive metal

                                        Mg


                                        Zn

                                        Cu    Least reactive metal

Salts
This word has come up many times and it always confuses people. A salt is a compound made when
a metal replaces the hydrogen in an acid. There are many salts that you use.

    1.   Common salt (sodium chloride)on your chips
    2.   Bath salts (sodium carbonate)
    3.   Low salt (potassium chloride) as a healthier alternative to common salt in cooking
    4.   Epsom salts (magnesium sulphate) for indegestion

The table below will help you understand the definition of a salt.
Naming salts
See how the name of the salt comes from the acid used.
Name of acid Formula of        Name of the salt made by        An example          Formula of the
               acid            the acid                                            example
Hydrochloric   HCl             Chlorides                       Sodium chloride     NaCl
acid
Sulphuric acid H2SO4           Sulphates                       Magnesium         MgSO4
                                                               sulphate
Nitric acid    HNO3           Nitrates                         Potassium nitrate KNO3
4. Chemical properties of non-metals
Non-metals react with oxygen and form oxides. There is a little description to guide you through each
one

Here sulphur powder is heated on a combustion spoon until it is on fire (blue flame). Then it is placed
in a gas jar of oxygen. The sulphur bonds with the oxygen making the compound sulphur dioxide.

S + O2        SO2

During lightning the high temperature cause the nitrogen and oxygen gases in the air to react and
combine. The nitrogen and oxygen molecules are given loads of energy by the lightning. They zoom
around and smash into each other and join. One nitrogen atom joins with two oxygen atoms to make
the compound nitrogen dioxide.

N2 + 2O2        2NO2

These non-metal oxides, sulphur dioxide and nitrogen dioxide, dissolve in water and form acidic
solutions. Acids are made when water reacts with non-metal oxides. The table below summaries this
for you.

Making acidic solutions from non metal elements
This table shows how you can change a non-metal element into an acid solution. It also shows you the
connection between the name of an acid and the non-metal element from which it was formed.

Non-metal     Name of compound formed            Formula Name of acid formed by             Formula of
element       through reaction with oxygen               dissolving this oxide in           acid
                                                         water
Sulphur       Sulphur dioxide                    SO2     Sulphuric acid                     H2SO4
Nitrogen      Nitrogen dioxide                   NO2     Nitric acid                        HNO3

								
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