All of the words you have ever heard, written, or read in the English language are merely just combinations of one or more of the 26 letters of the English language. And, those letters are just a combination of lines, curves, and dots. The number and arrangement of these basic pieces determine exactly what words are being communicated.
Matter can be described in much the same way. Just as all of the words in the English language are made up of combinations of the 26 letters of the alphabet, all matter is made up of atoms of different combinations of the 109 existing elements.
Additionally, just as each letter can be broken down into the three fundamental pieces of lines, curves, and dots, each atom can also be broken down into three fundamental pieces, called subatomic particles. The number and arrangement of these subatomic particles are what makes one element’s atoms different from the atoms of another element.
Dalton’s atomic theory
The first scientist to propose an atomic model was John Dalton (1766-1844). His theory, known as Dalton’s atomic theory, is the basis of our understanding of the nature of matter. The following four statements comprise Dalton’s atomic theory:
All matter consists of indivisible and discrete particles called atoms.
The atoms of any given element are identical; the atoms of different elements are different.
Atoms combine in small whole number ratios to form compounds.
When atoms combine, separate, or rearrange, a chemical reaction occurs. When an atom chemically combines with another atom to form a compound, it looses its characteristic properties. However, during a chemical reaction, atoms of one element are never converted into atoms of another element. In other words, atoms are neither created nor destroyed.
When we look around us, there are certain things which we see and there are certain things which are invisible to us. Everything in this universe is made up of material which scientist have termed as ‘matter’.
Physical nature of matter: Matter is made up of particles,
Properties of particles of matter
Particles of matter have space in between them:
Particles of matter are in a continuous state of motion: Particles, as they have kinetic energy, are continuously moving. This kind of movement is zigzag or random. This movement goes up on heating.
Particles of matter attract each other: Particles of matter attract each other with force, this force could be inter-atomic, inter molecular.
States of matter
The matter around us exists basically in three states, solid, liquid, and gas.
Solid state: the Solid state is character sized by definite shape, distinct boundaries, and fixed volume (negligible compressibility). Solids have a tendency to maintain the shape even if subjected to an external force. On applying force beyond their tolerance limit, a solid break down but tend to retain its shape that is rigidness. The intermolecular force of attraction between solid is strongest.
Liquid: They have fixed volume but no fixed shape. They take up the shape of the container in which they are put. Liquids flow and change shape, so they are not rigid but can be called a fluid. The intermolecular force of attraction between liquids is lesser than solids.
Liquids display diffusion: Liquids display a property which helps them in mixing with other solids and gases. Other particles get into the space between the particles of liquids and intermix.
Gases: Gases are highly compressible as compare to solids and liquids. The rate of diffusion is much faster in gases as to liquids. (How do you get attracted to kitchen, when something nice is being cooked), it’s possible due to diffusion. Gases have no definite shape or size. They occupy the space available to them. Force of attraction is least in gases. In the gaseous state, the particles move along randomly at high speed. Due to this high speed, the particles hit each other and also the walls of the container.
Interchanging of state of matter
Solids to liquids: On increasing the temperature of solids, the kinetic energy of the particles increases. Due to increase in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes the force of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage reaches when the solid melts to become a liquid.
Melting point: The temperature at which the solid is converted to liquid is called its melting point. The stronger the force of attraction between molecules, higher is the melting point of solid.
Latent Heat: When the solid is being converted to liquid or liquid is being converted to gas, Heat supplied is not able to increase the temperature of either solid or liquid, this heat is known as latent heat. The latent heat is required to overcome the force of attraction between particles.
a) Latent heat of fusion: Heat supplied when solid is converted to liquid.
b) Latent heat of vaporisation: Heat supplied when liquid is converted to gas.
Specific heat: Heat required increasing the temperature of either solid, liquid or gas is defined as specific heat.
Liquids to gases: When liquid is converted to gas on supplying heat, the process is known as evaporation.
Gases to liquids: When gas is cooled, it gets converted to liquid and the process is known as condensation.
Liquids to solids: If a liquid is cooled further, it gets converted to solid and the process is known as freezing.
Multiple choice questions:
Q.1 Matter displays three states.
c) Not sure
Q.2 Evaporation happens when
a) Solid is converted to liquid
b) Liquid is converted to solid
c) Liquid is converted to gas
d) Solid is converted to solid
Q.3 Melting temperature of ice:
a) 100 degree C
b) 100 degree F
c) 0 degree C
d) 10 degree C
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