Chapter 1.Matter In Our Surroundings

 

Introduction:

   We see different substances or objects around us. All the substances around us are not similar in their properties.Each substance  has its own properties based on the properties of the substances matter is classified into different groups. Can you guess based on which properties matters are classified?

    Before coming to your answer let's first know what is matter?

Anything which occupies space and has mass is called matter. The properties of matter is grouped into two categories that is physical properties and chemical properties.

Physical Properties:

    Physical properties are determined without changing the identity of the substance. The two different types of physical properties are intensive property and extensive property.

Intensive Property:

  It is a bulk property.It does not depend on the size or the amount of material in it. Examples; temperature, density, melting point, boiling point, refractive index and hardness of an object.If we make small pieces of a diamond they maintain their hardness.

Extensive Property:

   In simple it is a physical property that will change if the amount of matter changes. Example; mass (how much matter is present in a sample),volume (how much space does the sample takes up?) and length(how long is the sample?).

Chemical Properties:

    The property of a substance that is observed during a reaction in which the chemical composition or the identity of the substance is changed. For example when hydrogen reacts with oxygen the product formed is water in this example, the property of hydrogen is that it is a combustible gas, oxygen is a supporter of combustion whereas the product formed is water which neither is a combustible gas nor a supporter of combustion but, it helps in extinguishing fire. What do we observe here ?The property of the product formed is completely changed compared to the property of the reactants.

   Let's try to understand mass and volume in short. Mass is a large body of matter with no definite shape. The S.I unit of mass is kilogram expressed as kg. Volume is the amount of space that a substance object occupies, or that is enclosed within a container the S.I unit of volume is cubic metre expressed as m³.

   Early Indian philosophers classified matter in the form of five basic elements -air, earth, fire, sky and water.

   Modern day scientists have evolved to types of classification of matter based on their physical properties and chemical nature.

1.1 Physical Nature Of Matter

1.1.1 Matter is made up of particles:

   Let's try to understand the concept by performing a very simple activity.

Materials required: Two 100ml beakers, 2 to 3 spoons of common salt, a glass rod and a spoon or spatula.

Procedure:

🔴 Take 100 ml beaker and fill half the beaker with water and mark the level of water on the beaker.

🔴 Now add few spoon of common salt in the beaker containing water and note down your observation.

🔴 Now take the glass rod and stir the salt collected at the base of the beaker and note your observation.

Observation:

🔴 Salt settles down in the beaker containing water.

🔴 On stirring with the help of class rod, the particle starts disappearing and it disappears completely.

🔴 The level of the water remains the same.

Interference:

The particles of salt dissolves in water because water particles has space present in it.

  

  Hence we can come to a conclusion that matter is made up of particles.

1.1.2 How Small Are These Particles Of Matter

To understand the concept let's perform an activity.

Activity 1.2

    Take a glass or beaker having 100 ml of water in it. Ad two or three crystals of potassium permanganate to the beaker containing 100 ml of water.

     Now, take another beaker having 19 ml of water in it. Take 10 ml of solution from the first beaker and add it to the second with 90 ml of water.

      Once again take 10 ml of the solution and add it to the third beaker with 90 ml of water.

      Repeat the process 5 to 8 times in similar manner.

Observation:

      The colour of the solution becomes lighter in each beaker compared to the previous one.

Inference:

      This activity explains that a crystal of copper sulphate contains millions of tiny particles that keeps on dividing into smaller and smaller numbers with each dilution.

       We can conclude that there must be millions of tiny particles in just one crystal of potassium permanganate, which keeps on dividing themselves into smaller and smaller particles.

      Instead of potassium permanganate take 2 ml of dettol and perform the same activity.

      After performing the activity by taking detailed we can conclude that the smell of dettol can be detected even on repeated dilution.

    By performing this activities we conclude that the particles of matter are very small they are very very small beyond our imagination!!!