Write a note on composition of matter.

Harsh's mother asked him to close the knob of the gas stove after use, but he forgot. After some time, his mother observed a smell of rotten cabbages in the whole house. She went to the kitchen and saw that the knob was still open. She closed it immediately. Later, she made Harsh understand that it is very dangerous to keep the knob of the stove open, as it can catch fire.

(a) Which characteristic of gas is responsible for this smell in the whole house?

(b) Name the gases that a gas cylinder usually contains.

(c) Is it possible to keep solids and liquids compressed in a cylinder?

(d) What precautions should we follow to avoid any mishaps in the kitchen?

(e) What would you do in such a situation?

We can move our hands through air and water, but not through a wooden structure. Why?

In which of the following cases will the sugar dissolve in a glass of water faster, and why?

Case 1: Water in the glass is cold
Case 2: Water in the glass is warm