(a) List in tabular form three chemical ...

CBSE Class 10 Science 2019 Delhi Set 1

Question : 16 of 28

Marks: +1, -0

(a) List in tabular form three chemical properties on the basis of which we can differentiate between a metal and a non-metal.

(b) Give reasons for the following:

(i) Most metals conduct electricity well.

(ii) The reaction of iron (III) oxide

[\mathrm{Fe}_2\mathrm{O}_3]

with heated aluminium is used to join cracked machine parts.

Solution:

S.No	Metals	Non Metals
1.	They react with oxygen to form basic oxides. $\underset{\text{Magnesium}}{2\mathrm{Mg}} + \mathrm{O}_2 \rightarrow \underset{\text{Magnesium oxide}}{2\mathrm{MgO}}$	They react with oxygen to produce acidic or neutral oxides. $\underset{\text{Carbon}}{4\mathrm{C}(\mathrm{S})} + \mathrm{O}_2(\mathrm{g}) \rightarrow \underset{\text{Carbondioxide}}{\mathrm{CO}_2(\mathrm{S})}$
2.	They react with water to produce metal hydroxide and hydrogen gas. $\mathrm{Mg} + 2\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Mg}(\mathrm{OH})_2 + \mathrm{H}_2$ .	They do not react with water.
3.	Generally they do not combine with hydrogen except sodium, potassium, calcium which form ionic hydrides and they form positively charged ions.	They react with hydrogen to form covalent hydrides and they form negatively charged ions.

(b) (i) Metals for example

\mathrm{Na}

has an electronic configuration of 2, 8, 1 i.e. It has one free electron. This electron moves through the metal and conducts electric current due to the presence of free electron.

(ii)

\underset{\text{(s)}}{\mathrm{Fe}_2\mathrm{O}_3} + 2\mathrm{Al} \rightarrow \mathrm{Al}_2\mathrm{O}_3 + 2\mathrm{Fe}

(l)

It is thermite reaction

This reaction is an exothermic reaction. The reaction produces large amount of heat due to which iron metal is produced in molten form and use to join the tracks.

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