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Introduction to Chemistry

Chemistry is the systematic study of composition of matter and also the chemical and physical properties related to different material objects.

Lavoisier (1743-1793), a French Chemist is regarded as the Father of Modern Chemistry.

Matter – Any material that takes space, have mass and can be felt through senses is called matter.

Matter can be classified on the basis of Physical Properties and Chemical Properties.

On the basis of Physical Classification matter is of following three types-

Solid, Liquid and Gas

On the basis of Chemical Classification matter can be classified into following two types

Pure Substances and Mixture

Pure Substances- These have two categories 1. Element and 2. Compound

Elements are of three types- Metallic, Metalloids and Non Metallic

Compounds are of two types – Organic Compounds and Inorganic Compounds

Mixture can be classified into two sub groups – A. Homogeneous Mixture and B. Heterogeneous Mixture

Solid - Solid is one of the three classical states of matter (the others being gas and liquid). It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, either in a regular geometric lattice (crystalline solids, which include metals and ordinary water ice) or irregularly (an amorphous solid such as common window glass).

Liquid - Liquid is the classical state of matter with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms and molecules, held together by forces called chemical bonds. Water is, by far, the most common liquid on Earth. Liquid is one of the three classical states of matter (the others being gas and solid). Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena.

Gas - Gas is one of the three classical states of matter (the others being liquid and solid). Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point, boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms from within the gas.

Examples of solids- ice, coal, salt
Examples of liquid -water, mercury, alcohol
Examples of gas-water vapor, hydrogen, oxygen, nitrogen

Water is the only naturally known substance which exists in all three states- Ice is Solid Water, Water itself is liquid and Water Vapor is Gas.

Pure Substance-  A pure substance is a substance that cannot be separated by physical means. eg. filtration, evaporation, distillation or chromatography.

Examples of pure substances include water, gold, glucose, carbon dioxide, oxygen and hydrogen.

A pure substance is made up of one type of particle. The particle that makes up water is H2O. The particle that makes up carbon dioxide is CO2.

Elements- Elements is the simplest form of pure substance. Element can neither be created nor destroyed by simplest means of physical process or chemical synthesis.

Metals-A metal is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable, ductile and shiny. Some examples of Metal are Cobalt, iron, copper, and plutonium.

Mercury is only metal which found in liquid state.

Non Metals- Non-metals are the elements in groups 14-16 of the periodic table. Non-metals are not able to conduct electricity or heat very well. As opposed to metals, non-metallic elements are very brittle, and cannot be rolled into wires or pounded into sheets. The non-metals exist in two of the three states of matter at room temperature: gases (such as oxygen) and solids (such as carbon). The non-metals have no metallic luster, and do not reflect light.

The Non-Metal elements are: Hydrogen, Carbon, Nitrogen, Oxygen, Phosphorus, Sulfur, Selenium.

Metalloids- An element that is not a metal but that has some properties of metals. Arsenic, for example, is a metalloid that has the visual appearance of a metal, but is a poor conductor of electricity; metalloids are generally semiconductors. The elements classified as metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.

Compounds- Compound is a pure, macroscopically homogeneous substance consisting of atoms or ions of two or more different elements in definite proportions that cannot be separated by physical means. A compound usually has properties unlike those of its constituent elements.

Organic Compounds- The compounds containing carbon that are typically found in living systems are called organic compounds. The term organic is applied to hydrocarbons and their derivatives. Some of the examples of organic compounds are carbohydrates, proteins, oils, fats etc.

Inorganic Compounds- The chemical compounds obtained from non living sources are called Inorganic Compounds. Some of the examples of inorganic compounds are Aluminium chloride, Dihydrogen Mono Oxide or Water, Barium azide, Caesium bicarbonate, Carbon disulfide, Germane etc.

Mixture-  A mixture is a combination of two or more substances that are not chemically united and do not exist in fixed proportions to each other. Most natural substances are mixtures. Some of the examples of mixture are Milk, Sea Water, Petroleum, Paint, Glass, Cement, Wood Etc.

Homogenous Mixture - A substance that is uniform in composition is a definition of homogeneous. Some of the examples of homogenous mixture are sugar in water, salt in water, honey in milk benzene in toluene etc.

Heterogeneous Mixture: A heterogeneous mixture is made of different substances that remain physically separate. Heterogeneous mixtures always have more than one phase. Some of the examples of heterogeneous mixture are - Sand & water (liquid & solid), Carbonated beverage like soda or beer (gas & liquid), Orange juice with pulp in it (liquid & solid).

Separation of Mixture- Mixture can be separated by various methods. Some of the often practiced methods of separation of mixture are described below-


Sublimation is the terminology used for the process when matter undergoes a phase change from a solid to gaseous form, or vapor, without passing through the liquid phase. Some the examples of material that undergoes for sublimation process are dry ice, and frozen carbon dioxide.

Filtration - Filtration is the physical method of separation of mixtures commonly uses for the separation of solids from fluids (liquids or gases) by employing an intervening medium through which only the fluid can pass.

Evaporation - Evaporation is a type of vaporization of a liquid that only occurs on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs within the entire mass of the liquid.

Crystallization - Crystallization is a technique often practiced by chemists for purification of solid compounds. Crystallization is based on the principles of solubility i.e. ‘compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids.’ If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.

Distillation - Distillation is a popular technique for separating mixtures based on differences in the conditions required to change the phase of components of the mixture. To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back into liquid form and collected. Repeating the process on the collected liquid to improve the purity of the product is called double distillation. Although the term is most commonly applied to liquids, the reverse process can be used to separate gases by liquefying components using changes in temperature and/or pressure.

Distillation is widely used for many commercial productions, for example production of gasoline, distilled water, xylene, alcohol, paraffin, kerosene, etc.

Distillation has three types –
Simple Distillation
Fractional Distillation
Destructive Distillation

Melting Point - The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exists in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure.

Boiling Point - The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high-pressure has a higher boiling point than when that liquid is at atmospheric pressure. In other words, the boiling point of a liquid varies depending upon the surrounding environmental pressure. For a given pressure, different liquids boil at different temperatures.

Vapor Pressure - Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's evaporation rate. A substance with a high vapor pressure at normal temperatures is often referred to as volatile.


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