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3 X – Science
CHAPTER – 1
Chemical Reaction : – Whenever a chemical change occurs we can say that
a chemical reaction has taken place
eg – Food gets digested in our body
– Rusting of iron.
Chemical Equation :– A chemical reaction can be expressed symbolically
by using chemica...
METALS AND NON-METALS
q About 118 elements are known today. There are more than 90 metals, 22
non metals and a few metalloids.
q Sodium (Na), potassium (K), magnesium(Mg), aluminium(Al), calcium(Ca),
Iron(Fe), Barium(Ba) are some metals.
q Oxygen(O), hydrogen(H), nitrogen(N), sulphur(S), phosphorus(P), fluorine(F),
chlorine(Cl), bromine(Br), iodine(l) are some non-metals
*Physical properties of metals:
q Solid at room temperature except mercury
q Ductile (drawn into wires)
q Malleable (beaten into thin sheets)
q Sonorous(produce sound)
q Lustrous(natural shine)
q Have high melting point. Cesium and gallium have very low melting point.
q Generally good conductor of heat and electricity, except lead and mercury
which are comparatively poor conductors. Silver and copper are best
conductors.
q Have high density. Sodium and potassium can be cut with knife, they have
low density.
Physical properties of non-metals:
q Occur as solid or gas. Bromine is liquid.
q Generally bad conductors of heat and electricity. Graphite a natural form of
carbon is a good conductor.
q Non-sonorous.
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, q Non-lustrous, only iodine has lustre.
q Metals form basic oxides like Magnesium oxide(MgO), while non-metals
form acidic oxides (as in acid rain).
*Chemical properties of metals:
1. Reaction with air
Metals can burn in air, react or don't react with air.
Metal + oxygen → Metal Oxide
q Some metals like Na and K are kept immersed in kerosene oil as they react
vigorously with air and catch fire.
q Some metals like Mg, Al, Zn, Pb react slowly with air and form a protective
layer.
q Mg can also burn in air with a white dazzling light to form its oxide
q Fe and Cu don't burn in air but combine with oxygen to form oxide. When
heated iron filings burn when sprinkled over flame.
q Metals like silver, platinum and gold don't burn or react with air.
2Na + O2
→ Na2O
2Mg + O2
→ 2MgO
2Cu + O2
→ 2CuO
4Al + 302
→ 2Al2O3
Amphoteric Oxides : metal oxides which react with both acids as well as
bases to form salt and water e.g. Al2O3, ZnO.
Al2O3 + HCl
→ AlCl3 + H2 O
Al2O3 + NaOH
→ NaAlO2 + H2 O
2. Reaction with water :
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