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Q.15. (a) What is a reactivity series? Describe an activity to develop a reactivity series.
(b) Write two physical and two chemical properties of non-metals. 5

Ans. (a) The arrangement of metals in a vertical column in the order of their decreasing reactivities is called reactivity series of metals.
Activity:

• Some metals are chemically very reactive whereas others are less reactive e.g. potassium and sodium react vigorously with cold water so these are very-very reactive metals.
• Calcium reacts with cold water but not vigorously.
• Magnesium does not react with cold water but reacts with hot water.
• Aluminium and zinc react with steam so these metals are less reactive than Magnesium.
• Iron does not react with steam but red hot iron reacts with steam so iron is less reactive than aluminium and zinc.
• Whereas copper and silver do not react with water at all. So they are very-very less reactive metals.
  So on the basis of reaction of metals with water, we can arrange.
  K > Na > Ca > Mg > Al > Zn > Fe > Cu > Ag.

(b) Two physical properties of non-metals
• Non-metals are neither malleable nor ductile.
• Non-metals do not conduct heat and electricity.

Two chemial properties of non-metals
• Reaction of non-metals with oxygen
Non-metals react with oxygen to form acidic oxides or neutral oxides.

• Reaction of non-metals with chlorine
Non-metals react with chlorine to form covalent chlorides which are non-electrolytes.

Science 2009 Question Papers Class X
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