5th class unit 5 matter and changes in its states | 5th class effects of heat on arrangements of particles | melting | boiling

 Unit5:- 

        Matter And Changes in its States

5.1 Matter

We can see many types of things around us. In our class room there are chairs, tables, books, notebooks, pens, scales etc. What are the characteristics of these things? We can say that anything which has man and occupies is called matter. So soil, water, air, iron glass and wood are all matter. The substance is present three physical states.

1. Solid
2. Liquid
3. Gas

Following are the physical characteristics of states of matter.

1. Those substances which have fixed shape and definite volume are called solid. Particles of solids are tightly packed with one another. Examples are chair, pencils, and desks, etc.

2. Liquids do not have fixed shape. They assume the shape of the containers in which they are kept in. Liquids have definite volume.The particles of liquid are not tightly packed Examples are water and milk etc.

3. iii. The distance between the particles of gases is greater than solid or liquid Examples are air,oxygen,and hydrogen etc.

5.2 Sequence of matter 

Each state of matter is different from other because arrangement of particles in each state of matter is different.

Arrangement of particles in solids

In solids, particles are tightly packed due to the presence of strong attractive forces between them.Due to this reason, the particles only vibrate from side to side and spin around their fixed position.

Arrangement of particles in liquids

In liquids, the particles are not tightly packed. There are weak attractive forces between them as compared to solids.The particles,easily vibrate as they are not fixed in one place. Hence, liquids have no definite shape but liquids adopt the shape of the container in which these are poured.

Arrangement of particles in Gases

In gases, the distance between the particles is much greater than the solids and liquids.The attractive forces between the particles of gas are nearly negligible. So the gas particles move randomly and cover all the provided space. So there is nothing gases shape and volume.

5.3 Effect of heat on arrangement of particles

If a solid is heated, its particles get heat energy and begin to vibrate. But the vibration is not clear too much.

If a liquid is heated, its particles obtain energy. As there is less attractive forces between the particles, they move faster. If the particles absorb more and more energy, they change into vapours and escape from the surface of liquid.

If the gas is heated, the particles move in all directions. They collide with each other and then change direction.

5.4 Processes involving changes in states

Following are the processes which occur when one state of matter changes into another.

1. Melting

Melting is the  process of converting a solid changes into a liquid. When we increase the temperature of solids, the energy of particles increases.Due to increase in energy, the particles start vibrating with greater speed. The energy supplied by  heat controls the forces of attraction between the particles.The particles leave their fixed positions and start moving freely. A stage comes when solid melts and converts into a liquid. This process is called melting.

2. Boiling

Boiling is the process in which liquid changes into vapours on heating. Water boils at 100°C. When a liquid is heated, its particles get energy which overcomes the forces of attraction between them. As a result, they start to move in all directions. If the particles gain more heat energy, they become more excited and may escape as vapours from the surface of liquid. This process is called boiling.

3. Freezing 

The process in which liquid converts into solid is called freezing.Water freezes at 0°C. When the temperature of liquid decreases, the energy of its particles decreases. As a result, its particles cannot move and eventually stop at this stage,the liquid concerts into a solid.

5.5 Different forms of moisture in the environment

when aquifers are heated during the day,a large portion of the water  evaporates into the air.this air gets hot.The hot air rises up carring the water vapours with it. As the wind rises, it expands and cools This cooling causes the water vapours in the air to condense in tiny droplets. Once the droplets form and they grow bigger by the condensation, they fall down in the form of rain, fog, dew, frost and snow.

1. Dow

In the morning water droplets are seen on the surface of leaves and grasses, this is called dew. As there is a moisture in the air and due to the condensation of these droplets dew is formed.

ii. Snow

Snow is a form of precipitation. The water vapours present in clouds at greater heights turn into frozen ice-crystals. These ice crystals join together to form snow flakes which slowly fall to the Earth's surface.

iii. Fog

In winter morning, closer to the ground, the water vapours suspended in air form fog. Due to fog, visibility in the winter morning reduces.

iv. Frost

When the temperature of air falls below the freezing point, small white crystals are formed on the surface of ground. It is called frost.

v. Rain

Winds having water vapours cool down at height in the sky and condense to form clouds. The tiny droplets of water present in the clouds join together and fall towards the Earth's surface as rain