States of Matter and Its Properties Class 9 Notes | EduRev

MATTER

• Anything that occupies space and has mass is called matter. In other words, they have both mass and volume.
• It exists in the form of five basic elements, the Panch tatva – Air (Vayu), Earth (Prithvi), Fire (Agni), Sky (Aakash) and Water (Jal).

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.

• Matter is categorized as a gas, a liquid and a solid on the basis of the physical state.
  Example: Air, Water and ice.
  Changes of state are also matters of everyday experience.
  Example: Ice melts and water freezes, water changes into steam on heating and steam condenses to liquid water on cooling.
• On the basis of chemical nature, matter is classified as an element compound or mixture. Elements and compounds are pure substances whereas a mixture contains two or more pure substances.

Material
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.

• Take about 50 ml water in 100 ml beaker.
• Mark the level of water.
• Add some salt to the beaker and stir with the help of a glass rod.
• Observe the change in water level.
  

  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

• Take a 250 ml beaker and add 100 ml water to it.
• Now add 2-3 crystals of potassium permanganate (KMnO₄) and stir with a glass rod in order to dissolve the crystals.
• Take 10 ml of this solution and add to 100 ml of water taken in another beaker.
• Take 10 ml of this diluted solution and put into 100 ml of water taken in still another beaker.
• Repeat this process 10 times observe the colour of the solution in the last beaker.
  

  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

• The smell of food being cooked in the kitchen reaches us even from a  considerable distance.
• When someone opens a bottle of perfume in one corner of a room, its smell spreads in the whole room quickly.
• The leakage of cooking gas (LPG) in our homes is detected due to the diffusion of a strong smelling substance present in the cooking gas, into air.

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.

• Take a piece of iron wire, a piece of chalk and a rubber band.
• Try to break them by hammering, cutting or stretching.

Observation

• Hammering a piece of the iron nail does not break the nail but flatten its surface.
• Hammering chalk breaks the chalk and gives us powdered chalk.
• We can stretch the rubber band to a large length without any break.

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

• A solid possesses a fixed volume and a definite shape, distinct boundaries and a definite mass.
• Solids are rigid and almost incompressible.
• Solids may break under force but it is difficult to change their shape.
• Solids generally possess high densities.
• Solids do not exhibit diffusion.
• In solids, intermolecular forces of attraction are stronger.
  Example: Table, Chair, Common Salt, Silver, Ice, Diamond, Stone, Sugar etc.

Fig: Example of solid matter

Example of solid state

• A wooden block should be called a solid.
  Explanation: A wooden block has a fixed shape and is rigid. Hence, it should be called solid.
• A rubber band undergoes a change in shape on stretching, still, we call it a solid because it regains the same shape when the force is removed.

Solids generally do not exhibit diffusion: Due to smaller inter-particle spaces and absence of translatory motion.

Some examples in which solids show diffusion

• If we write something on a blackboard and leave it uncleaned for a considerable period of time (say, at least 10 to 15 days), we will find that it becomes quite difficult to clean the blackboard afterwards. This is due to the fact that some of the particles of chalk have diffused into the surface of backboard.
• If two metal blocks are bound together tightly and kept undisturbed for a few years, then the particles of one metal are found to have diffused into the other metal

2. Liquid state
Properties of Liquids

• The matter in liquid state possesses a definite volume, a definite mass, but no definite shape.
• Liquids are also almost incompressible but are not rigid. In fact, they can flow from a higher to a lower level. Liquids have a property of fluidity and acquire the shape of the container in which they are kept.
• Liquids can undergo diffusion.
• Liquids also have high densities but less than that of solids.
• In liquids, inter-molecular forces of attraction are weaker than solid.
  

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

• The matter in gaseous state has neither definite volume nor definite shape but it has a definite mass. It acquires the shape and volume of the container.
• Gases are highly compressible.
  

  Fig: Evaporation, an example of gaseous matter

• Activity: To demonstrate air is compressible while water and solid are not Activity wants us to fill three syringes, each with one type of object viz, water, chalk powder, and air and ask us to compress it.

• Observation: With some force, we are able to compress the syringe filled with air while other syringes are completely non-compressible.
• Explanation: Solid, liquid and gases have a different amount of spaces between their constituent molecules. A solid has the least space between the molecule which does not move; while gases have the largest intermolecular spaces. When we compress a gas its intermolecular space decreases. Since gases have large intermolecular space, we are easily able to compress it with force. While in the case of liquid and solid has small intermolecular space makes it completely impossible to compress.
• Conclusion: This experiment demonstrates that gases are compressible while liquids and solids are not.

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