Unit‐2 States of matter
Matter: It is something that occupies space possessing certain mass. Hence all the Substances present in this universe are matters.
Classification of matter on the basis of their physical state:
On the basis of physical state, matter can be classified as solid, liquid, gas and plasma.
Solid: Matter which possesses definite mass , volume and shape are called solids.In this state particles are held very close to each other.These particles have no freedom of movement. Ex: Wood, stone, copper etc. Liquid: Matter which possesses definite mass and volume but indefinite shape are called liquid. In this state particles are close to each other and they can move within their volume. Ex: water,Benzene,carbon tetrachloride, kerosene. Gas: Matter which possess definite mass but indefinite volume and shape are called gases. In gases particles are far apart as compared to solid and liquid. The particles can move freely from one point to another.Ex: Nitrogen, Oxygen, Carbon dioxide etc.
Plasma: It is a highly ionized gas, made up of almost equal number of positive ions and negative electrons. It is formed only at a extremely high temperature of the order of 50000C. It is described as the fourth state of a matter.Plasma is believed tobe the main constituent of stars including sun.
Note: The fifth state of matter is called Bose‐Einstein condensate (BEC). This state occur at the end of the temperature scale at a step above absolute zero Kelvin.
Classification of matter on the basis of composition:
On the basis of the chemical composition matter can be classified as fallows.
1. Heterogeneous matter 2. Homogeneous matter
1) Heterogeneous matter: A substance is heterogeneous if it exhibits different properties at its different position. Different types of heterogeneous matter are a)suspension b) colloid c) heteromixture
Heterogeneous matter Homogeneous matter ______
Suspension colloid Hetero.mixture Homogeneous mixture Pure substance
Metal Non‐metal metalloid
a) Suspension: It is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.These particles can be seen by the naked eye. The solute particles settle down when the suspension is left undisturbed. These can be separated from the mixture by the process of filtration.
Ex: dirt particles in water, soar milk.
b) Colloid: Colloids are the heterogeneous mixture of two components with the size of the particle is 1nm to 100nm(or 10 A0 to 1000A0).These particles of colloid are uniformly spread throughout the solution. Due to relatively smaller size of the particles as compared to the mixtures ,It appears to be homogeneous, but actually colloids are heterogeneous. These are possessing two phases.(Dispersed phase and dispersion medium)
c) Heteromixture: It is obtained by mixing two or more substance in any ratio. These are possessing the mixed properties of the combined substance.These can be separated by physical method.
Ex: A mixture of sand and common salt. 3
2) Homogeneous matter: A substance is a homogeneous matter if the smallest part of it exhibits the same chemical and physical properties. Ex: Air , Solution of sugar with water, an intimate mixture of two or more than two metals (alloys).
Homogeneous matter can be classified into two types.
a) Homogeneous mixtures b) Pure substances
a) Homogeneous mixture: A mixture of two components that appears in a single phase is called homogeneous mixtures. These are called as solutions.
A homogeneous mixture of solute and solvent are called solutions. These solutions are also called as true solutions or crystalloids
Ex:A homogeneous mixture of sugar and water gives true solutions.
b) Pure substance: These are made of only one type of particles such as atoms or molecules. Further these are classified as elements and compounds.
Element: Simple forms of matter which cannot be decomposed into further simple substances are called elements. 118 elements are discovered till today, out of which 92 are naturally occurring elements and remaining are artificially prepared elements.
Ex: Hydrogen, mercury, gold, iron etc.
Elements are further classified as metals, non‐metals and metalloids
Metal:The elements with the electro‐positive nature of losing one or more electrons readily to give positively charged cations are called metals.
M M++ e‐
Non‐metal: The electronegative elements which have a tendency to gain one or more electrons are called non‐metals. After getting the electrons negative ions formed are called anions. A is a non‐metal and A‐is anion.
A + e‐ A‐
Ex: Chlorine, Bromine, sulphur etc
Figure 1 Magnesium metal Figure 2 Sodium metal
Metalloids: Elements possessing properties of both metals and non‐metals are called metalloids.
Ex: Antimony, arsenic, Germinium etc.
Compounds: The substances made of two or more than two elements combined with each other in a definite ratio by mass are called compounds. These can be decomposed into its elements by chemical or electrochemical reactions.
Ex: 1. In water(H2O) number of hydrogen and oxygen atoms are in the ratio 2:1 or it contains hydrogen and oxygen combined with each other in the ratio of 1:8 by their mass. i.e. 2g of hydrogen combines with 16 g of oxygen .
2. Sulphuric acid (H2SO4 ):In this compound the ratio of number of atoms of H:S:O combined is 2:1:4. The ratio by mass of H:S:O is 1:16:32.In this compound 2 g of hydrogen 32 g of sulpher 64 grams of oxygen combine with each other to form 98 g of H2SO4.
Solution: A homogeneous mixtures of solute and solvent are called solutions. In a solution, a substance which is in a less quantity is solute and other which is in more quantity is solvent. In aqueous solution of sugar, water is solvent and sugar is solute.
Concentration of solution. The amount of a solute present in a unit volume of the solution is called concentration of the solution. 5
Concentration of the solution can be expressed in terms such as percentage by mass or by volume, molarity,molality, normality, mole fraction,ppm.Out of these terms the most familiar terms to express the concentration of the solution are percentage by mass or volume, molarity and normality.
Percentage by mass: It is the mass of the solute present in 100 g of the solution.