Question

C. Long answer type questions
1 Give reasons for the following-
a) Expansion and contraction are maximum in gases.
b) Silver pieces of jewellery tarnish when exposed to air.
c) Apples and some other fruits turn brown when cut surface is exposed to air.​

Answer 1

Question :-

a) Expansion and contraction are maximum in gases.

Answer :-

Expansion and contraction are maximum in gases because the particles of gases are very loosely packed when it contact with fire. By heating expansion is maximum in gases.

Question :-

b) Silver pieces of jewellery tarnish when exposed to air.

Answer :-

Silver pieces of jewellery tarnish when it is exposed to air because of hydrogen sulfide (sulfur) it is found in air. When it contact to air. A chemical reaction takes place and a black layer is formed. Actually it oxidized faster in places with a lot of light and high humidity.

Question :-

c) Apples and some other fruits turn brown when cut surface is exposed to air.

Answer :-

Apples and some other fruits turn brown when cut surface is exposed to air. Because apples and some fruits releases oxygen which is present in the cell of cutting surface of apples and some fruits. When it contact to oxygen then a reaction take place then it formed an enzyme( polyphenol). It mixes with it and starts the process of oxidation. This process is called oxidation of enzyme ( polyphenol). It causes the fruits and apples trun brown when it is exposed to the air.

Answer 2

Answer:

Required Answer :-

1] Expansions and contraction are maximum in gases

As we all know that there are three states of matter :-

Solid

Liquid

Gas

Now,

The question is asked why the gases expands and contracts more. The gases contracts or expand more due to their intermolecular structure. As their molecule are very loosely and have a lot of space. So, they may move easily. And for contraction the gases are actually have more space to contact with fire

2] Silver pieces of jewellery tarnish when exposed to air.

As we know that Silver is element and due to the reaction of $\sf H_2S$. Due to it the silver pieces jewellery tarnish.

3]

This is due to because the oxygen present in it released and thus it becomes brown. And if we cut and leave it for few hours the sometime due to unfavorable condition it will become brown