Shri krishna Stationers - Agra
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| Address : | Paschimpuri Road. Post Office ke Bagal Me, Agra, Uttar Pradesh 282007, India |
| Phone : | 📞 +9899 |
| Postal code : | 282007 |
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★ ★ ★ ★ ★ Have you seen wooden bells in
temples? Can you give a reason?
The things made of metals produce
a ringing sound when struck hard.
Suppose you have two boxes similar in
appearance, one made of wood and the
other of metal. Can you tell which box
is made of metal by striking both the
boxes?
Since metals produce ringing
sounds, they are said to be sonorous.
The materials other than metals are not
sonorous.
After performing the above activities,
we can say that some materials are hard,
lustrous, malleable, ductile, sonorous
and good conductors of heat and
electricity. The materials which
generally possess these properties are
called metals. The examples of metals
are iron, copper, aluminium, calcium,
magnesium, etc. In contrast, materials
like coal and sulphur are soft and dull
in appearance. They break down into a
powdery mass on tapping with a
hammer. They are not sonorous and are
poor conductors of heat and electricity.
These materials are called non-metals.
The examples of non-metals are sulphur,
carbon, oxygen, phosphorus, etc.
which rust is formed. You had also
performed in Class VII an activity of
burning a magnesium ribbon in air. You
had learnt that in both the processes
oxide formation takes place. Complete
the following reactions of iron and
magnesium with oxygen.
Iron (Fe) + Oxygen (O2
) + Water (H2O) → ?
Magnesium (Mg) + Oxygen (O2
) → ?
Activity 4.3
Let us check the nature of rust
formed as a result of the reaction
between iron, oxygen and water.
Collect a spoonful of rust and
dissolve it in a very little amount of
water. You will find that the rust
remains suspended in water. Shake
the suspension well. Test the
solution with red and blue litmus
papers (Fig. 4.3). What do you
observe? Is the solution acidic or
basic?
Metals like sodium and potassium are
soft and can be cut with a knife.
Mercury is the only metal which is
found in liquid state at room
temperature. These are exceptions.
4.2 Chemical Properties of
Metals and Non-metals
Reaction with Oxygen
You are familiar with the phenomenon
of rusting of iron. Recall the reaction by
Rust
Rust
suspension
Red litmus
paper
Fig. 4.3 : Testing the nature of rus
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