World of Matter – Maharashtra Board Class 9 Solutions for Science and Technology (English Medium)
AlgebraGeometryScience and TechnologyHindi
Solution 1:
- Camphor and naphthalene are sublimatory substances.
- On heating, solids get converted to liquids and liquids get converted to gases.
- We usually find matter in solid, liquid and gaseous forms.
Solution 2.1:
Solution 3.1:
Substances which are lighter in weight float. The density of ice is less than that of water. Hence, ice floats on water.
Solution 3.2:
In solids, the particles are very closely packed. Also, the force of attraction between the particles is very strong. They cannot move away from each other. Hence, solids have a definite shape.
Solution 3.3:
A gas is liquefied by lowering its temperature below a particular temperature, which is characteristic for the given gas and then applying high pressure.
Solution 4.1:
- In the gaseous state, particles move with random motion at high speed. So, these particles collide with the walls of the container and with each other too.
- Force per unit area is known as pressure. Thus, they exert force on the walls of the container.
- Therefore, gas exerts pressure on the walls of the closed container.
Solution 4.2:
As compared to solids and liquids, gases are highly compressible. So, a large volume of gas can be compressed into a small cylinder and easily transported to the places where it is used as a fuel for vehicles and cooking. Hence, in the LPG cylinder, the gas filled is in the liquefied state.
Solution 5:
- At 257°C, water is in the gaseous state in the form of steam.
- At 100°C, water gets converted to the gaseous state if heat is supplied continuously.
- At 0°C, water gets converted to the solid state, i.e. ice, provided heat is removed from it.
Solution 6:
- Particles of matter are continuously moving. They possess kinetic energy.
- The smell of food reaches us because of the process of diffusion of the aroma of the particles of food into the air.
- As the temperature raises, the kinetic energy of particles raises and the rate of diffusion also rises.
- Thus, we get the smell of hot food several metres away, but to get the smell of cold food, we have to go close to it.