D. C. Pant 💻

Chemical Reactions A chemical reaction is a change in which one or more substances or reactants reacts to to form new substances with different properties. The reacting species (molecule, atom or ion) are known as reactants (the substances that undergo chemical change in the chemical reaction) and the new species formed as a result of the reaction are called products (the new substances formed during reaction).   2Na (s) + 2H 2 O (l) → 2NaOH (aq) + H 2(g) ↑ In the above chemical reaction , sodium hydroxide and hydrogen are the products and sodium and water are the reactants.     Identification of chemical reaction A chemical reaction can be identified by either of the following observations – (i)                 Change in state (ii)              Change in colour (iii)            Evolutio...

Chapter – 2 Is Matter Around Us Pure     Question 1. Which separation techniques will you apply for the separation of the following?   (a) Sodium chloride from its solution in water. -------Evaporation.   (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. -------Sublimation   (c) Small pieces of metal in the engine oil of a car. ------Filtration   (d) Different pigments from an extract of flower petals. -------Chromatography     (e) Butter from curd. ------------Centrifugation   (f) Oil from water. ---------Separating Funnrl   (g) Tea leaves from tea. ---------Filtration   (h) Iron pins from sand. -------------Magnetic Separation   (i) Wheat grains from husk. ------------ Sieving   (j) Fine mud particles suspended in water. --------- sedimentation and then filtration.     Question 2. Write the step...

  NCERT BOOK QUESTIONS AND EXERCISES Chapter 1 : Matter in Our Surroundings Part – 3  Question 1- Convert the following temperature to the Celsius scale :            (a)                       293 K              (b) 470 K  Answer – (a) Temp. On Kelvin scale = Temp. on Celsius scale + 273 293 = temperature on Celsius scale + 273 So, temperature on Celsius scale = 293 – 27       = 20 o C (b) Temp. On Kelvin scale = Temp. on Celsius scale + 273 470 = temperature on Celsius scale + 273 So, temperature on Celsius scale = 470 – 273         = 197 o C   Question 2 – Convert the following temperature to the Kelvin scale -        (a)                 ...

  NCERT BOOK QUESTIONS AND EXERCISES Chapter 1 : Matter in Our Surroundings Part – 2 Question 9 . Convert to following temperature to Celsius scale : (a)            300 K                          (b)     573 K Answer : (a) We know that : Temperature on Celsius   scale = temperature on Kelvin   scale – 273                                         = 300 – 273                                       ...