Example: Chair, bed, river, mountain, dog, tree, building, etc.
Fig: Matter around us
Classification of Matter
The matter can be classified into different categories depending upon its physical or chemical nature.
The term used to describe a particular kind of matter, is called material.
Example: Wood, Water and Marble.
PHYSICAL NATURE OF MATTER
1. Matter is made up of particles
The particle nature of matter can be demonstrated by a simple activity.
Fig: Apparatus for experiment
Observation: It is observed that the crystals of salt disappear. The level of water remains unchanged.
Explanation: A water molecule consists of hydrogen and oxygen atom. Between hydrogen and oxygen, there are large empty spaces. We call these empty spaces a
Void: When we add salt to the water, it goes into that void. As a result, we do not see any change in volume.
Conclusion: This activity shows that, Matters are made of small particles. And there is space between these particles.
2. The constituent particles of matter are extremely small in size
Fig: Mixture of water and potassium permanganate
Observation: When we add potassium permanganate in water, the colour of water changes to pink. Dilution decreases the colour intensity of the solution.
Explanation: A small amount of Potassium permanganate contain millions of its molecules. When we dissolve potassium permanganate in water, its molecule spread uniformly in the solution and give a pink appearance. Dilution lowers the amount of the particles in subsequent solution. As a result, we see a lower colour intensity.
Conclusion: A visible particle may have a large number of smaller particles in it.
CHARACTERISTICS OF PARTICLES OF MATTER
1. Particles of matter are continuously moving
If an incense stick (Agarbatti) is lighted and placed in one corner of a room, its pleasant smell spreads in the whole room quickly. It demonstrates that the particles of matter possess motion. When we light an incense stick, it produces some gases (vapour) having a pleasant smell. The particles of these gases due to motion spread in the entire room. As a result, we can observe the smell of the lighted incense stick from a long distance.
This shows that, Matters consist of small particles which are moving continuously. This means that particles of matter possess kinetic energy.
Fig: Incense sticks
Activity: To demonstrate that the kinetic Energy of particles increases with increase in temperature.
Kinetic energy: Kinetic energy is the energy of motion and is usually defined as the work that will be done by the body possessing the energy when it is brought to rest. For a body of mass m having a speed v, the kinetic energy is 1/2 mv2
(i) Take two beakers. To one beaker add 100 ml of cold water and to the other beaker add 100 ml of hot water.
(ii) Now add some crystals of potassium permanganate or copper sulphate to both the beakers.
Observation: It is observed that crystals in hot water diffuses and dissolves faster than in a beaker containing cold water.
Conclusion: All substances have some kinetic energy in it. When we heat a substance its kinetic energy increases. Heating water results in an increase in its kinetic energy, as a result, we see that crystals dissolves in much lesser time. From these activities, it is observed that when two different forms of matter are brought into contact, they intermix spontaneously. This intermixing is possible due to the motion of the particles of matter and also due to the spaces between them.
"This spontaneous intermixing of particles of two different types of matter is called diffusion".
Fig: Diffusion is a natural phenomenon and never stops
In our daily life, we make use of diffusion in many places. We add sugar in water to make tea or juices; here sugar molecule diffuses into the water through diffusion. A plant produces oxygen; this oxygen diffuse into the air and we get oxygen for breathing.
Note: The rate of diffusion becomes faster with an increase in temperature because, at a higher temperature, the particles have more energy and hence move faster.
Other examples of diffusion
2. Particles of matter attract each other
There are some forces of attraction between the particles of matter which bind them together. The force of attraction between the particles of the same substance is known as cohesion.
The force of attraction (or cohesion) is different in the particles of different kinds of matter. In general, the force of attraction is maximum in the particles of solid matter and minimum in the particles of gaseous matter.
The following activity may be carried out to demonstrate the attractive forces between particles of matter.
Conclusion: Since energy is required to break crystals of matter into particles. It indicates that particles in the matter are held by some attractive forces, the strength of these attractive forces varies from one matter to another.
STATES OF MATTER
Fig: Different states of matter
Matter can be classified into 3 states on the basis of physical state- Solids, Liquids and Gases.
1. Solid state
Properties of solids
Fig: Example of solid matter
Example of solid state
Solids generally do not exhibit diffusion: Due to smaller inter-particle spaces and absence of translatory motion.
Some examples in which solids show diffusion
2. Liquid state
Properties of Liquids
Water molecules in a container are in continuous motion, As a result they do not have own shape and flow easily.
Examples: Water, Alcohol, Milk, Diesel, Petrol, Kerosene Oil, Vegetable Oil, Fruit Juices etc.
Fig: Liquid matter
Solids, liquids as well as gases can diffuse into liquids This is due to the fact that the interparticle spaces in liquids are larger and the particles in liquid state move freely.
3. Gaseous state
Properties of Gases
Fig: Evaporation, an example of gaseous matter
Explanation of solid, liquid and gas state on the basis of molecular structure:
In the above figure, a, b and c show the magnified schematic pictures of the three states of matter. The motion of the particles can be seen and compared in the three states of matter.
Comparison of characteristic properties of solids, liquids and gases