Gas is the state of matter in which inter-particle space is large and inter-particle attraction is weak. Because of this, the particles become completely free to move randomly in the entire available space. Kinetic molecular theory of gases: The kinetic molecular theory of a gas states that a gas is composed of molecules/ particles which […]
Pure water is a colorless, transparent, clear liquid at room temperature. It is odorless and tasteless. When water is cooled, it first contracts in volume just like other liquids up to 4°C. On further cooling, it expands instead of contracting. This expansion takes place up to 0°C. Thus, at 0°C, water has maximum volume and
Atoms are indivisible particles. Atoms can neither be created nor destroyed. The atoms of an element are alike in all respects and differ from atoms of other elements. Atoms are divisible into sub-atomic particles such as protons, neutrons, and electrons. Atoms can be created and destroyed by nuclear fusion and fission. Atomic Structure and Chemical
Hydrogen is the first element of the periodic table. It was discovered by Cavendish and named by Lavoisier. Hydrogen belongs to the first group and the first period of the periodic table. Although the properties of hydrogen should be similar to those of the other members of the first group, this is not the case.
Anything which occupies space or volume has mass, and can be perceived by our senses is called matter. All materials are made up of matter. Matter exists in different forms or states. Matter in any state is composed of small particles—molecules, atoms, or ions. The matter is made up of tiny particles. These particles have
Pollutant: A pollutant is defined as undesirable matter present in excess in the environment. Atmospheric pollution: It is defined as the effect of undesirable changes occurring in our surroundings which has harmful effects on plants, animals, and human beings. Air pollution: It is defined as the presence of a contaminant in the atmosphere in a
In 1829, Dobereiner classified elements with similar chemical properties into groups of three called Triads. He noted that the atomic weight of the middle element in a triad is the arithmetic mean of the other two. This is called Dobereiner’s Law of Triads. Newlands proposed a Law of Octaves which states, ‘When elements are arranged
The specific abbreviation used to denote the name of an element is called its symbol. In 1807, John Dalton, a scientist, tried to name the various elements based on pictorial symbols. Symbols of some elements as proposed by Dalton are shown in the diagram. In 1814, the Swedish Chemist Jöns Jakob Berzelius devised a system
A chemical reaction is a process of breaking the chemical bonds of the reacting substances (reactants) and making new bonds to form new substances (products). A chemical bond is a force that holds the atoms of a molecule together, as in a compound. A chemical reaction occurs when two substances are mixed in their solid