Page 55 - Science Class 08

Extraction : To obtain a natural resource or element from its source, generally the earth

Occurrence : The incidence of availability of a substance at its source
Noble metals : Three metals, silver, gold and platinum that are generally non-reactive
Alloy : A uniform mixture of two or more metals or a matter and non-metals

Corrosion : Wearing away of the surface of a substance due to the action of another

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i The elements in-between metals and non-metals are called metalloids.
i Non-metals have their own properties and are useful in their own ways.
i Various non-metals are obtained from various sources in various manners.
i Non-metals have their own physical and chemical properties.
i Non-metals combine with oxygen to form oxides.
i Non-metals do not react with water.

i Most non-metals do not react with acids.
i Non-metals are useful in various ways.
i Alloys are uniform mixtures of metals or metals and non-metals.

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Exercise
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A. Tick (3) the correct op on.
1. ____________ inside of a metal quickly lose electrons in order to make posi ve ions or
ca ons.
(a) Atoms (b) Ions
(c) Chemical compunds (d) Compounds

2. Copper sulphide, when heated, gives copper and:
(a) iron oxide (b) copper dioxide
(c) sulphur dioxide (d) none of these

3. Aluminium is a silvery metal that has:
(a) medium weight (b) very light weight
(c) very heavy weight (d) in gaseous form
4. The name pla num comes from the Spanish word:

(a) Plate (b) Plata
(c) Pla um (d) Plite
B. Write the correct term for.

1. the elements –gold and pla num : _______________________
2. the elements that are neither metals nor non-metals : _______________________

Science-8 55