Matter in our Surroundings Chemistry 9th Class Chapter 1

Entire Universe is Made Up of Matter and Energy, Air, Water, Steam, Petrol, Carbon Dioxide, Silver, gold, Oxygen, Wood, Paper Etc. are all Different Kinds of Matter. All These Occupy Space (Volume) and have Mass.

Definition: A Matter is Defined as Anything that Occupies Space (Volume) and have Mass are Matter.

Classification of Matter 

There are Two Ways of Classifying the Matter:

  1. Physical Classification.
  2. Chemical Classification.

In Physics Classification, the matter is Classified on the Basis of Physical Properties and it is classified as Solids, liquids, and Gases. In chemical classification, the matter is classified on the basis of chemical properties and its classified elements, compounds, and mixtures.

Matter is Made Up of Tiny Particles

Every Matter is made up of tiny particles. The number of tiny particles in every matter is very, very large. The tiny particles which make up the matter are so small that they can not be seen even by a powerful microscope, It is important to know that the particles which make up the matter are either atoms or molecules.

Diffusion

Definition of Diffusion: The Process of interfixing the particles of two or more substances on their own is called Diffusion.

Diffusion occurs in solids, liquids, and gases, Diffusion is fastest in gases and slowest in solids. It decreases in Order. Diffusion is due to the motion of the particles of matter. The rate of Diffusion increases with the increase in temperature. It is because the speed and kinetic energy of the particles increases with the increase in Temperature.

Diffusion in Solids

Diffusion in Solids is very very Slow. It is because the position of particles in solids is fixed and they do not move from their fixed positions. Secondly, it is due to the small kinetic energy of particles in solids that Diffusion in Solids is very very Slow.

Diffusion in Liquids

Since the Particles of Liquids move slower than those of gases, liquids diffuse at slower rate than gases. The rate of diffusion of liquids also depends on their density, The Greater the density, the smaller is the rate of Diffusion, and vice-versa, The rate of Diffusion of liquids is faster than the rate of diffusion in Solids.

Diffusion in Gases

The particles of gas move at high speed in all directions. Therefore, diffusion in gases is very fast. The fragrance of food which is being cooked in the kitchen can be detected at a distance much away from the kitchen. The fragrance of a burning incense stick (agarbatti), the fragrance of a perfume, and the leakage of cooking gas (LPG) can be detected at a distance much away from the place where they have been placed. When a bottle of perfume is kept open, the vapours of the perfume mix with air, and move quickly in all directions and the whole room is full of the fragrance of the perfume.

Factors Affecting of Rate of Diffusion: 

  1. Density: The smaller the Density, the greater is the rate of Diffusion and vice-versa.
  2. Temperature: The Rate of diffusion increases with the increase in temperature.
  3. Physical State: Solids diffuse into liquids slowly whereas liquids diffuse into liquids faster.

Classification of Matter based on Physical States

Based on physical state matte is classified into three categories:-

  1. Solids: Sugar, Common Salt, Iron, sand, ice, wood, book, pencil, etc. are Solid.
  2. Liquids: Water, petrol, kerosene, milk Etc. are Liquids.
  3. Gases: Air, steam, oxygen, carbon dioxide, hydrogen, nitrogen, Etc. are gases.

Properties of Solids

  1. They have fixed shapes and definite volume.
  2. Solids are rigid and have fixed boundaries.
  3. They have negligible compressibility because intermolecular space is very small.
  4. Solids have high densities as compared to liquids and gases.
  5. Solids may Break under force but it is difficult to change their shape, so solids are rigid.

Properties of Liquids

  1. Liquids have fixed volume but their shape is not fixed.
  2. Liquids flow and change their shape, so they are not rigid.
  3. They have low compressibility but more than Solids.
  4. Liquids have a low density as compared to Solids.
  5. The Particles are not Closely packed in liquids. Therefore, the interparticle space in them is more than that of Solids.

Properties of Gases

  1. Gases have neither a fixed shape nor a fixed volume.
  2. Gases do not have definite boundaries.
  3. They can flow in all directions, thus gases show fluidity
  4. Gases have very low densities as compared to liquids and solids.
  5. The kinetic Energy of the Particles of gases is much more than that of Liquids or Solids.

Can Matter Change Its State

We know that water can exist in three states of matter:

(1) Solid as ice, (2) Liquid as water, (3) Gas as Steam or Water Vapour :

The state of a Substance depends upon temperature and pressure. By changing temperature and/or pressure, one form of state can be converted into the other form of state. For example on heating ice (solid), it gets converted into water (liquid). Water (liquid) on heating gets converted into vapour (gas).

Melting Point: The temperature at which a solid, melts to become a liquid at one atmospheric pressure is called its melting point.

It is important to know that the melting point of a solid is a measure of the force of attraction between its particles. The higher the melting point, the greater is the force of attraction between its particles. The melting point of ice is 0° C (273 K) and that of iron is 1535° C (1808 K). This shows that the force of attraction between the particles of iron is much more than those of the particles of ice.

Freezing Point: The temperature at which a liquid freezes to become a solid at one atmospheric pressure is called its freezing point.

Freezing is the reverse of melting: So, the freezing point of a liquid and the melting point of its sold is same. For Example, melting point of ice is 0° C and Freezing point of water is also 0° C.

Boiling Point:The Temperature at which a liquid boils and changes into vapour (gas) at one atmospheric pressure is called its boiling point of a liquid is a measure of the force of attraction between its particles.

Boiling point of water is 100° C (373 K) and that of methanol (methyl alcohol) is 64°C (337 K). This shows that the force of attraction between the particles (molecules) of water is much more.

 

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