Page 96 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

The table given below shows the melting point, boiling point and density
of some metals. Analyse the table.
Melting Boiling Density Melting Point and
Metal
–3
point (°C) point (°C) (g cm ) Boiling Point
Iron 1538 2861 7.873 Solid substances can be melted
Silver 961 2162 10.500 into liquid. We know that ice melts

Gold 1064 2836 19.281 to form water and if this water is
heated, it transforms into vapour.
Tungsten 3414 5555 19.254 It is thus possible to bring about

Titanium 1670 3287 4.508 changes in the state of any solid
substance. The temperature at
Copper 1084 2562 8.933
which a solid changes into liquid is
Chromium 1907 2671 7.194 called its melting point and that at

Table 7.2 which a liquid boils and changes
into gas is called its boiling point.
Based on the above discussions, we can now
summarise the general physical properties of metals.

• High thermal conductivity • High density
• High electrical conductivity • Malleability See the section 'Lohangal'
• Sonority • Ductility in School Resources in
IT@School Edubuntu
• High melting point

Given below are situations which make use of some physical properties of
metals. Complete the table.

Use Property
To make electric wires

To make aluminium foils to wrap food Can be beaten into thin
materials sheets
To make utensils
To make farming tools
To make bells used in places of worship

Table 7.3
Thus, metals have certain physical properties in common. Do they show
similarity in their chemical properties as well?
You might have observed the following :
• Iron articles kept outside our houses get destroyed through rusting
over a period of time.

• Gold, silver and platinum are usually used for making ornaments.
• Buttermilk is not stored in aluminium vessels.
• Verdigris (clav) is formed on copper vessels.

Basic Science VIII 95