ICSE Physics Class 8 Notes Chapter 1 Matter
→ Matter : Every substance living and non-living that we see is made up of matter and MATTER “is something which has mass, occupies space and can be perceived by our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar etc.
→ Matter is composed of tiny particles called molecules, which are in constant motion, have spaces between them and have inter- molecular attraction.
→ Every molecule can exist freely in nature and has all the properties of matter. A molecule is composed of ATOMS, but atom cannot exist free in nature.
→ INTER-MOLECULAR FORCE : “The molecules of a matter exert a force of attraction on each other – The force of attraction is called INTER-MOLECULAR FORCE: This force in solid is very strong and we cannot break a solid easily. In liquids this force is less strong and in molecules of gas it is very less.
→ FORCE OF COHESION : “The inter-molecular force of attraction between the molecules of same substance is called FORCE OF COHESION.” i.e. between water and water.
→ FORCE OF ADHESION : “The force of attraction between the molecules of two different substances is called FORCE OF ADHESION” i.e. between glue and paper.
Matter is composed of tiny particles and molecules of matter have spaces between them can be proved by experiment. Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt gets dissolved in water and still level remains at 50 c.c. Where has salt gone ?
The salt molecules enter into spaces of water and water molecules into spaces of salt molecules. This experiment show that particles of matter are very minute and cannot be seen by naked eye and there are spaces between molecules.
The molecules of matter are in constant motion can be seen by opening a bottle of perfume in a comer of room, it reaches the other parts of the room.
→ SUBLIMATION : Change of solid directly into vapours on absorbing heat.
→ DEPOSITION : “The change of vapours directly into solid on cooling.”
→ MELTING: “Change of solid in liquid at fixed temperature on heating.”
→ FUSION or FREEZING : “Change of liquid to solid state on cooling at a fixed temperature.”
→ FUSION or MELTING: “Change of a solid to liquid state at a fixed temperature on absorbing heat.”
→ EVAPORATION : Surface phenomenon i.e. only takes place at surface “Is change of liquid to vapours.” Evaporation has cooling effect. Takes place at all temperatures.
→ VAPORIZATION : “Change of liquid to vapour state on heating at constant temperature.” It is fast process and produces hotness