Kinetic theory of Matter [ 1860 ]

It states that matter is composed of many small particles called atoms that are in constant motion.

postulate 1

Matter is made of atoms or molecules. It is difficult to see molecules with the naked eye.

postulate 2

molecules are always in constant motion in a gas, meaning they are always in a continuous random zig-zag motion. This motion helps spread fragrance around.

postulate 3

when heat is added to a substance, its kinetic energy increases.

temperature is directly proportional to

kinetic energy

postulate 4

The molecules of matter are always exerting forces on each other. Force of cohesion: the force that exists between the same kinds of particles. Force of adhesion: the force that exists between different types of particles.

postulate 5

The particles of matter have spaces between them. The intermolecular forces are inversely proportional to the intermolecular spaces.

Bose- Einstein Condensate

it is a state of matter that occurs at temperatures close to 0 K, where particles behave as one single quantum entity.

characteristics of solids

1. least intermolecular space 2. most intermolecular force 3. fixed shape and size due to the intermolecular forces 4. cannot be compressed 5. definite volume 6. they do not expand much on heating 7. molecules cannot flow

characteristics of liquids

1. it has moderate intermolecular spaces 2. they have less intermolecular force than solids 3. the molecules are not fixed and can hence move around and slide past each other, although they are still bound together 4. it takes the shape of the container it's in 5. it has a definite volume 6. it can expand on heating

characteristics of gases

1. A lot of intermolecular space 2. least intermolecular force 3. The molecules are nearly independent due to their negligible intermolecular forces 4. the molecules show constant zigzag motion 5. they occupy all the spaces given to them 6. it can be compressed 7. it can expand on heating

melting/ fusion

it is a physical process that involves the change of state from a solid to a liquid on heating.

latent heat

the heat taken in or given out by a substance while it is changing state. this heat is used only to break the bonds of the molecules without actually altering its temperature.

melting with reference to kinetic theory

Molecules in a solid are tightly packed together. When heat is supplied, the molecules gain kinetic energy and start vibrating. The vibrations push the molecules apart, and once they reach the melting point, the molecules gain sufficient energy to overcome the forces of attraction. Then, the molecules stop being bound together and can move freely.

freezing

it is a physical process that involves a liquid changing to solid on cooling.

melting point is equal to

freezing point

boiling

it is a physical process in which a liquid changes to gas on heating.

specific latent heat of fusion

the amount of heat required to change a unit mass of substance from solid to liquid without change in temperature.

specific latent heat of vaporization

the amount of heat required to change a unit mass of substance from liquid to solid without change in temperature.

condensation

it is a physical process in which a gas changes to a liquid on cooling.

evaporation

it is a physical process in which a liquid changes to gas on heating at any temperature below its boiling point.

factors affecting the rate of evaporation

1. presence of wind 2. moisture content of air 3. surrounding temperature 4. nature of the liquid 5. area of exposed surface 6. temperature of the liquid

evaporation with reference to kinetic theory

when heat is supplied to the liquid, its particles gain kinetic energy. the particles at the surface gain the most energy. when the surface particles gain just enough kinetic energy to break away from the liquid, the average kinetic energy of the liquid reduces.

why do liquids not have a fixed shape

this is because the molecules have weak intermolecular forces. this means that the particles can slide past each other. however, the molecules are still bound together. which prevents them from expanding and makes sure they maintain a fixed volume.