II. Long Answer Questions :
1. What is meant by particulate nature of matter? List four characteristics of
particle nature of matter.
2. List three characteristics of particles of matter. Describe one example for each
caracteristics to illustrate it. Name the characteristics which are responsible
for
(a) spreading of smell of scent in a room and
(6) water taking the shape of the vessel in which poured.
3. Give reasons for the following:
(a) Gases fill up completely the vessel in which they are kept.
(6) Gases exert pressure on the wall of the containing vessel.
4. The temperature time graph given below shows
110°C
C
the heating curve for pure wax. From the graph
answer the following:
(a) What is physical state of substance at point ОС
с с
A, B, C and D.
D
D1
Temperature
Bi
15°C LAB
(b) What is the melting point of the substance?
A1
(c) What is its boiling point?
AB
(d) Which portions of the graph indicate that change of state is taking place.
(e) Name the terms used for heat absorbed during change of states involved in above process.
5. What is the name of phenomenone of changing a liquid into its vapour at a
temperature below its boiling temperature?
Answers
Answer:
These are the four main characteristics of particles of matter
Particles of matter are very tiny in size: When a teaspoon of salt is dissolved in one or two litres of water, every drop of that water taste salty. When few drops of Dettol are mixed in water, whole water gives the smell of Dettol. Even after diluting this dettol mixed water, it gives the smell of dettol. This proves that particles of matter are very small.
They have space between them: We can move our hand through the air easily. To move our hand in liquid, such as water, we have to apply some force, but for a solid such as wood, we cannot move our hand. This is because the force of attraction between particles of gas is almost negligible, in liquid the forces of attraction is moderate but it is greatest in solid.
Particles of matter move constantly: Example: Diffusion and Brownian motion give the evidence that particles are in motion.
They are attracted towards each other: For example, breaking a chalk is easier than breaking a nail. This proves that attraction varies from particles of one substance to another. Cohesion means the force of attraction between the particulate matter of the same substance.