Rakesh Garhwal

Concentration of Solutions Solutions-An Overview Large amount of salt is dissolved in seawater. This makes it unfit for drinking directly. Can we say that the amount of salt in the sea is the same everywhere? The air contains gases like oxygen, carbon dioxide and ozone along with various small particles like pollen grains and dust. Are the gases and the particles present in equal amounts in air? Soil contains a lot of substances, e.g., clay, organic matter, minerals, pebbles, etc. Why do the amounts of clay, organic matter, minerals, etc. in soil vary from place to place? All of the above substances (soil, air and seawater) are examples of mixtures. Let us go through the lesson to find out what mixtures are. Mixtures A mixture may be defined as a material having two or more types of pure forms of matter. For example, milk is a mixture as it contains a combination of water molecules, fat molecules and protein molecules. The constituents of a mixture can be separated by certain physical ...

Earlier Atomic Models and Subatomic Particles The Atomic Model  Atom Is Divisible Do you recall  Dalton’s atomic theory ? Dalton postulated in his theory that an  atom is   indivisible . However, the later discoveries of protons and electrons proved this to be erroneous.  In 1886, while carrying out an experiment in a gas discharge tube, E. Goldstein discovered positively charged radiations which led to the discovery of the subatomic particles called protons. Later, in 1897, J. J. Thomson discovered another type of subatomic particle—the negatively charged electron. Consequent to these discoveries, an atom was no longer indivisible; rather, it became a sum total of differently charged subatomic particles. We know that an atom is neutral. It is made up of an equal number of oppositely charged particles—protons and electrons. Now, the question that arises is this: How are the subatomic particles arranged inside an atom? Many scientists performed var...