Thursday, April 30, 2020

Chemistry: About Basic Units : Matter

Basic Terms of Chemistry

1.Matter: Simply, Anything that has mass and occupies space.

Fig 1. Classification of Matter

Physical Classification of Matter:
  • Solid: Generally hard and rigid. In other words they have definite shape and definite volume. e.g. wood, table, rod etc.
  • Liquid: Generally takes shape of container, and they have definite volume but indefinite shape for e.g. water, oil, milk etc.
  • Gaseous(Gas): Generally occupies whole containers. in other words have neither definite shape nor definite volume. foe e.g. air, Oxygen etc.
 Chemical Classification of Matter: 
  1.  Pure Substances: The portion of matter that has definite physical and chemical properties. As in fig 1 it classified into two types a) elements b) compound. 
a) Elements: It is the simplest form of the pure substance. It can neither be built nor be destroyed     by any physical or chemical method. It is further divided into three types
i) Metal ii) Non-Metal iii) Semi-Metal.
i) Metala solid material that is typically hard, shiny, malleable, fusible, and ductile, with good        electrical and thermal conductivity. e.g. Gold, Silver, Copper etc.
ii) non-metal: A non-metal is a chemical element that mostly lacks the characteristics of a metal.     Physically, a non-metal tends to have a relatively low melting point, boiling point, and density.        they has no-lustrous and having poor electrical and thermal conductivity. e.g. some of gases like      hydrogen, neon etc., some time Metalloids such as boron, silicon, and germanium are sometimes    counted as nonmetals. 
iii)  Semi-metal: These elements have characteristic (properties) of both metal and non metal. Common complex's are silicon, Bismuth etc.

b) Compound: A substance which is formed by adding two or more elements in definite proportion of weight, is called compound. This can be further decomposed by chemical methods. The compound is the chemical   combination of elements. It further divided into two types.
i) Inorganic Compound: Which are obtained from non-living sources like rocks, minerals etc. 
e.g. salt, marbles. 
ii) Organic Compound: Which are obtained from living sources such as animal's and plant's.
e.g. carbohydrates oils fats.

   2.  Mixture. It is combination of two or more compounds and elements. It can be combined in any form. And the components that are combined don't lose their identity.
1) Homogeneous : (Homo means same kind) When two components completely mix in uniform composition. It has no visible boundaries of separation. e.g. sugar in water
2) Heterogeneous: (Hetro means different kind) When components don't mix completely and also has not in a uniform composition. They consist of phases (one or more) .it has visible boundaries of separation between the constituents. e.g. mixture of sand and water.

Questions may arise :

1. What is the difference between mixture and compound?
2. Differentiate the following:
a) Metal and Non-metal
b) Homogeneous and Heterogeneous Mixture.

Some of the important terms to be taken into account:
Atom: we can say atom is the fundamental piece of matter. or An atom is the smallest unit constituting a matter.
Molecule: A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. e.g. HCl- is made up of one hydrogen atom and a chlorine atom.
Subatomic Particles Of Atom:
1. Electron ( ): It is a particle carrying one unit negative charge(1.6022×10^-19C) and has a mass (9.1×10 ^-31 k.g.) Essential constituent of all atoms.
2. Proton (p or p + ) : A particle which carries one unit positive charge (same as electron) and has mass (1.67×10-^27 kg)
3. Neutron (n or n 0):  A subatomic particle which has no electrical charge and has a mass of (same as proton).

Atomic number(Z) = no. of protons (p)+ no .of electrons (e)
Mass number(A)= no. of protons (p)+ no. of neutrons(n).
NOTE:  Number of electrons =Z
              Number of protons =Z
              Number of neutrons=A-Z
where A is the mass number.
e.g.  Boron, which has atomic number Z = 5 and mass number A = 11. Calculate the number of protons, electrons, and neutrons.
since no. of electron = no. of proton = 5
therefore no. of neutron = A-Z 
          = 11-5
          = 6

Questions may arise :
1. Define the terms (i) Atom (ii) Molecules.
2. What are the sub-atomic particles of Atom? describe.
3. Consider Lithium which has atomic number Z = 3 and mass number A = 7. Calculate the number of protons, electrons, and neutrons. 

To Be Conti.........
Reference: Above data is collected from NCERT books, Google, Wikipedia and our knowledge 

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