Composition of Water
* The chemical formula of water was established by S. Cannizzarro as H2O.
* The process of decomposing water into its constituent elements called electrolysis of water.
* Hydrogen and oxygen combine in the ratio of 2:1 by volume to from water.
* The gravimetric or mass ratio of hydrogen to oxygen is 1:8 in water.
Water Dissolves Many Substances
* Solvent is defined as a liquid which dissolves other substances in itself.
* Water allows the dissolution of all substances over a period of time so it is a known as universal solvent.
* Substances that dissolve in a solvent are called solutes. For example, salt and sugar.
* When a solute gets dissolved in a solvent the product formed is known as solution.
* Solution of any substance in water is known as its aqueous solution.
* The substances which get dissolved rapidly in water are called soluble substances while the ones which dissolve slowly are called insoluble substances.
Physical and Chemical Properties of Water
* Water is the universe solvent and can dissolve most substances.
* Water is a colourless, odourless and tasteless liquid.
* The freezing point of water is zero degrees, and boiling point is 100°c.
* Water reacts with certain metals to produce metal hydroxides.
* Steam reacts with some metals to produce metal oxides.
* Metallic oxides produce metal hydroxides, whereas non – metallic oxides produce acids.
Is Matter Around Us Pure
* A solution is a homogeneous mixture of two or more substances.
* The component of the solution that is present in a large amount is called the solvent.
* The component of the solution that is relatively present in a smaller quantity is called the solute.
* Concentration is defined as the amount of solute present in unit volume of a solution.
* A solution in which no more solute will dissolve is called saturated solution. A solution in which more of the solute will dissolve is called unsaturated solution.
* Solubility is the maximum amount of the solute by weight in grams dissolved in 100 grams of solvent at a constant temperature.
* A suspension is a heterogeneous mixture in which the solute particles do not dissolve and remain suspended.
* A colloid is a heterogeneous mixture in which the particles cannot be seen with the naked eye.
* The dispersed particles in a colloid form the dispersed phase.
* The component in which the dispersed phase is suspended is known as the dispersing medium.
* The phenomenon of the scattering of light by colloidal particles is called the Tyndall effect.
Acids, Bases and Salts – Salts
* A compound formed by the reaction between an acid and base is known as a salt.
* Salts are solids and ionic compounds.
* Based on the strength of the reacting acid and base, salts are classified into neutral, acidic and basic salt.
* Sodium chloride is obtained from the sea and used to preserve pickles, to manufacture soaps, to melt ice and in the preparation of other compounds.
* Salts which have a fixed number of water molecules as an essential part of their crystal are called hydrate salts.
* Plaster of Paris is used as a bandage, proofing materials, and a sealing agent and for making statues, toys and decorative articles.
