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ACIDS :

This content is part of NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts

Substances with sour taste are regarded as avoids. Lemon juice, vinegar, grape fruit juice and spoilt milk etc. taste sour since they are acidic. Many substances can be identified as acids based on their taste but some fo the acids like sulphuric acid have very strong action on the skin which means that they are corrosive in nature. In such case it would be according to modern definition-

           An acid may be defined as a substance which release one or more H+ ions in aqueous solution.

           Acids are mostly obtained from natural sources. One the basis of their source avids are of two types -

             (a) Mineral acids                                           (b) Organic acids

 4.1 (a) Mineral Acids :

             Acids which are obtained from rocks and minerals are called mineral acids.

 4.1 (b) Organic Acids :

CONGRUENT AND SIMILAR FIGURES:

This content is part of NCERT Solutions for Class 10 Maths Chapter 6 Triangles

Two geometric figures having the same shape and size are known as congruent figures. Geometric figures having the same shape but different sizes are known as similar figures.

8.2       SIMILAR TRIANGLES:

               Two triangles ABC and DEF are said to be similar if their

               (i)            Corresponding angles are equal.

                               i.e. ÐA = ÐD, ÐB = ÐE, ÐC = ÐF

                               And,

INTRODUCTION:

This content is part of NCERT Solutions for Class 10 Science Chapter 4 Carbon and its Compounds

           Organic compounds: The compounds like urea, sugars, fats, oils, dyes, proteins vitamins etc., which were isolated directly or indirectly from living or indirectly from living organism such as animals and plants were called organic compounds. The branch of chemistry which deals with the study of these compounds is called ORGANIC CHEMISTRY.

 12.2     BONDING IN CARBON = THE COVALENT BOND :

           Most carbon compounds are poor conductors of electricity. The boiling and melting points of the carbon compounds are low. Forces of attraction between these molecules of organic compounds are not very strong/ As these compound are largely non conductors of electricity hence the bonding in these compound does not give rise to any ions.

           The reactivity of elements if explained at their tendency to attain a completely filled outer shell, that is, attain noble gas configuration. Element forming ionic compounds achieve this by either gaining or losing electrons from the outermost shell. In the case of carbon, it has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration. It is were to gain or lose electrons –

 (i)         it could gain four electrons forming C4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons, that is, four extra electrons.