Matter in our surrounding class 9th notes
Introduction
In our surrounding, we see large things with different shapes, sizes and textures. Everything in this universe is made up of material have named “matter”. The air we breathe, the food we eat, stones, clouds, stars, plants and animals, even a small drop of water or a particle of sand – everything is matter. They have MASS and VOLUME.
Matter may be defined as anything that occupies space possesses mass and the presence of which can be felt by any one or more of our five senses.
- It is important to note that heat, light, sound, electricity, magnetism, etc. Are not considered as matter because they are massless and do not occupy space. Similarly, vacuum is not a matter since it neither occupies space nor has mass.
According to ancient Indian philosophers, all matter whether living or non-living is made up of five basic constituents commonly called panchtatvas, i. e, air, earth, fire, sky and water. A similar classification of matter was also evolved by ancient Greek philosophers.
Scientists have classified matter into the following two types on the basis of their properties:
- Physical classification- On the basis of physical properties, matter has been classified as solids, liquids and gases.
- Chemical classification- On the basis of chemical properties, matter has been classified as elements, compounds and mixtures.
Characteristics of particle of Matter
Particles in matter are in a state of continuous motion not stationary, but have a tendency to acquire motion. The rate of movement of the particles is directly proportional to the thermal energy of the particles.
Particles in matter attract one another: This attraction is inversely proportional to the distance between the particles. However, the magnitude of these inter-particle forces differs from one substance to another.
Particles in matter have spaces between them: Empty spaces called voids. This separates the particles from one another. The distance between them ranges from 10-8 cm to 10-5 cm. Due to these voids matter is able to disperse into one another bringing about diffusion.
State of matter
The classification of matter into three different states, namely solid, liquid and gaseous state is termed as the physical classification of matter. Most properties of solid, liquid and gases that can be observed with our sense organs are called as ‘macroscopic’ properties.
The description of the behaviour of the three states of matter in terms of atomic theory is called ‘microscopic’ description of matter. From the study of the observable properties of different states of matter one can understand the microscopic nature of matter in terms of the behaviour of constituent particles.
Solid
The molecules in a solid are very closely packed. When the solid is heated, molecules gain more kinetic energy and vibrate more, inter-molecular distance increases and the solid expands. Example: Iron, wood, stone, sand, gold, ice, pencil, book, needle, piece of thread, etc
PROPERTIES of Solids STATE
Some of the common properties of solids, which distinguish them from other two states of matter, are:
- Solids are rigid and have definite shapes.
- Solids have definite volume irrespective of the size or shape of the container in which they are placed.
- Solids are almost incompressible.
- Many solids have a crystalline appearance and have definite pattern of angles and planes.
- Solids diffuse very slowly as compared to liquids and gases. Constituent particles are very closely packed in solids permitting very little space for their movement.
- Solids have a much higher density (mass to volume ratio) than that of gases and liquids.
- Most solids become liquids when heated. Some undergo sublimation on heating. The temperature at which a solid changes into liquid is called the melting point and the process is called as melting. Due to the varying natures of solids their melting temperatures vary considerably.
Liquid
Molecules in liquids have vibratory motion as well as strong translatory motion. Thus, the molecules of a liquid can move freely within the liquid. As a result, liquids don’t have a fixed shape. It takes up the shape of the container. Example: Water, milk, petrol, kerosene oil, alcohol, cooking oil, cold drink, etc
PROPERTY OF Liquid State
- Due to weak intermolecular forces, the molecules are in constant random motion.
- The average kinetic energy of molecules in a given sample is proportional to the absolute temperature.
- Liquids do not have a fixed shape but have a fixed volume
- Liquids are not rigid but have the property to flow.
- Liquids possess the property of diffusion
Gas
The molecules of a gas are far apart. The inter-molecular force of attraction is negligible, and they have no fixed freedom of motion. Hence gases have neither fixed shape nor volume. Example: Air, oxygen, nitrogen, hydrogen, ammonia, carbon dioxide, compressed natural gas (CNG), etc.
Properties OF Gaseous State
- Gases do not have fixed shape
- Gases have minimum fluidity and least rigidity:
- Gases do not keep their volume and are highly compressible
- Gases are generally very light
- Kinetic Energy of a particle in the gaseous state is very high
- Gases exert pressure
- Gases diffuse rapidly (The rate of diffusion of a gas is inversely proportional to the square root of its density. This is called Graham’s Law of diffusion.)
Plasma
Plasma is much like gases except that their constituent particles have become electrically charged, and their behaviour in consequence depends strongly upon electromagnetic forces. Most of the matter in the universe is in the plasma state.
Example: A fluorescent tube contains plasma (When electricity is passed, the gas gets ionized and glowing plasma is formed. The colour of this glowing plasma depends upon the nature of the gas). The sun and the stars glow due to the presence of plasma. The plasma in stars is formed due to high temperature.
Temperature
Temperature is defined as the measure of average heat. On the other hand it is defined as the thermal energy of the particles in a substance. Temperature is independent of the number of particles or size and shape of the object. The water boiling temperature is same for all type of containers.
- By adding or removing heat, the temperature of a substance can be increased or decreased.
- The device which is used to define the measure of temperature of an object is Thermometer.