Notes for ch 1 matter in our surroundings of class 9th
Answers
Matter, its definition and caracteristics
Diffusion and its Applications
Brownian Motion
States of Matter
Interconversion of Three States of Matter
Evaporation
Basic physical quantities and their SI units:
Key notes for Chapter- Matter in Our Surroundings, are:
Matter:
Anything that occupies space and has mass is called matter.
It exists in the form of five basic elements, the Panch tatva – air, earth, fire , sky and water.
For example: Chair, bed, river, mountain, dog, tree, building, etc.
Characteristics of matter:
Matter is made up of small particles called atoms.
These particles are too small to be observed with naked eye.
These particles are constantly moving constantly.
These particles have spaces between them.
Particles of matter attract each other because of the force of attraction.
Diffusion:
Particles of matter intermix on their own with each other. They do so by getting into the spaces between the particles. This intermixing of particles of two different types of matter on their own is called diffusion.
Applications of Diffusion:
Dissolving a solid in a liquid:
When a crystal of potassium permanganate is placed in a beaker of water, the water slowly turns purple on its own, even without stirring.
Both potassium permanganate crystal and water are made up of tiny particles.
When the potassium permanganate crystal is put in water, the purple colored particles of potassium permanganate spread throughout water making the whole water look purple.
Actually, on dissolving, the particles of potassium permanganate get into the spaces between the particles of water.
This shows that the particles have spaces between them and are continuously moving on their own.
Mixing of two gases:
Fragrance of an incense stick (agarbatti) lightened in one corner of a room, spreads in the whole room quickly.
The particles of gases (or vapours) produced by burning the incense stick move rapidly in all directions and mix with the moving particles of air in the room
This also shows that the partices of matter are constantly moving.
Brownian motion of particles (By Robert Brown):
The random or zig-zag movement of microscopic particles in a fluid, as a result of continuous bombardment from molecules of the surrounding medium, is known as Brownian motion.
For example: Dust moves randomly because the random moving particles of air collide with dust particles.
Explanation:
States of Matter
Matter can be classified as solid, liquid and gas on the basis of interparticle forces and the arrangement of particles.
These three forms of matter are interconvertible by increasing or decreasing pressure and temperature. For example, ice can be converted from solid to a liquid by increasing the temperature.