Some Basic Concepts of Chemistry Notes

Importance of Chemistry

Chemistry is impacting our life and has many applications in many fields. Given below are some application of chemistry

In Industry

For the development of industrially manufactured fertilizers, soaps, alkalis, acids, salts, dyes, polymers, drugs and other things.Chemistry is important in development and growth of a number of industries.Chemistry helps our industry produce more materials—such as paints, plastics, iron or steel, cement, kerosene and also motor oil.


In protecting Crops

Protecting from insects and harmful bacteria, by the use of certain effective insecticides, fungicides and pesticides.Chemistry also helps farmers to enrich the soil with chemicals.

In Education

Chemistry education plays an important role in enhancing the quality of teaching and research.Chemistry is essential for meeting our basic needs of food, clothing, shelter, health, energy, and clean air, water, and soil. Learning chemistry allows students to learn about the scientific method and gain skills in critical thinking and deductive reasoning.


Anything which occupies space and has mass is called matter. Examples of matter are bat , ball , car , plane and book are composed of matter as they have mass and they occupy space.

Classification of Matter

There are two ways of classifying the matter:

1. Physical classification

2. Chemical classification

Differences between Compounds and Mixtures

Two or more elements are combined chemicallyMany elements or compounds are simply mixed and not combined chemically
The elements are present in the fixed ratio by mass and ratio cannot be changedThe constituents are not present in fixed ratio. The ratio can vary
The Compounds are always homogeneous in natureEither homogeneous or heterogeneous in nature
The constituents cannot be separated by physical methodscan be separated by physical methods.

Laws of Chemical Combinations are:

(i) Law of Conservation of Mass

According to the law of conservation of mass in a chemical reaction mass is neither created nor destroyed. For example, when wood burns, the mass of the soot, ashes, and gases equals the original mass of the charcoal and the oxygen when it first reacted. So the mass of the product equals the mass of the reactant.The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.

(ii) Law of Definite Proportions

In chemistry, the law of definite proportions, sometimes called Proust's law, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio and does not depend on its source and method of preparation.The law of definite composition has applications to both molecular compounds with a fixed composition and ionic compounds as they require certain ratios to achieve electrical neutrality.

(iii) Law of Multiple Proportions

In chemistry, the law of multiple proportions states that if two elements form more than one compound, then the ratios of the masses of the second element which combine with a fixed mass of the first element will always be ratios of small whole numbers.For example, there are five distinct oxides of nitrogen, and the weights of oxygen in combination with 14 grams of nitrogen are, in increasing order, 8, 16, 24, 32, and 40 grams, or in a ratio of 1, 2, 3, 4, 5.

(iv) Gay Lussac’s Law of Gaseous Volumes

Gay-Lussac's law (also called as Amonton's law) states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas when the volume is kept constant.Example of Gay-Lussac's law is pressure cookers. When the cooker is heated, the pressure exerted by the steam inside the container increases. The high temperature and pressure inside the container is the reason for food to cook faster.

(v) Avogadro’s Law

Avogadro's law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. Avogadro's law tells the relationship between the amount of gas (n) and volume (v) . Avogadro's Law is in evidence whenever you blow up a balloon. The volume of the balloon increases as you add moles of gas to the balloon by blowing it up. If the container holding the gas is rigid rather than flexible, pressure can be substituted for volume in Avogadro's Law.