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Diffusion in solids, liquids and gases






Diffusion:

  • The spreading out and mixing of a substance with another substance due to the motion of its particles is called diffusion.
  • The diffusion of one substance into another substance goes on until a uniform mixture is formed. For example: diffusion of bromine vapors in air. 
  • Diffusion is the property of matter which is based on the motion of its particles. Diffusion occurs in gases, liquids and solids.
  • Diffusion is fastest in gases and slowest in solids.
  • The rate of diffusion increases on increasing the temperature of the diffusing substance.

Diffusion in Gases:

  • Diffusion in gases is very fast. This is because the particles in gases move very quickly in all directions.
  • The rate of diffusion of a gas, however, depends on its density. Light gases diffuse faster than heavy gases.
  • Example: When we light an incense stick (agarbatti) in a corner of our room, its fragrance spreads in the whole room very quickly due to the diffusion of its smoke into the air.


Diffusion in liquids:

  • Diffusion in liquids is slower than that in gases. This is because the particles in liquids move slowly as compared to the particles in gases.
  • Example: The spreading of purple colour of potassium permanganate into water, on its own, is due to the diffusion of potassium permanganate particles into water.
  • Note: The gases like carbon dioxide and oxygen are essential for the survival of aquatic plants and animals. The carbon dioxide and oxygen gas present in air diffuse into water, and dissolve in it. The aquatic plants use the dissolved carbon dioxide for preparing food by photosynthesis and aquatic animals use the dissolved oxygen of water for breathing. This is an example of diffusion of gases into a liquid.

Diffusion in solids:

  • Diffusion can also takes place in solids. Diffusion in solids is very, very slow process.
  • Example: If we write something on a blackboard and leave it uncleaned for a considerable period of time, we will find that it becomes quite difficult to clean the blackboard afterwards. This is due to the fact that some of the particles of chalk have diffused into the surface of blackboard.



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Class 9 Maths Class 9 Science
Reference Books for class 9 science

Given below are the links of some of the reference books for class 9 science.

These books by S.Chand Publications are detailed in their content and are must have books for class 9 students.
  1. Science for Ninth Class Part1 Physics
  2. Science for Ninth Class Part2 Chemistry
  3. Science for Ninth Class Part3 Biology
Some other books that might be worth considering are
  1. Oswaal CBSE Question Bank Class 9 Science Chapterwise & Topicwise We all know importance of practicing what we have studied. This book is perfect for practicing what you have learned and studied in the subject.
  2. Pearson Foundation Series (IIT-JEE/NEET) Physics, Chemistry, Maths & Biology for Class 9 (Main Books) | PCMB Combo These Foundation books would be helpful for students who want to prepare for JEE/NEET exams. Only buy them if you are up for some challenge and have time to study extra topics. These might be tough for you and you might need extra help in studying these books.
  3. Foundation Science Physics for Class - 9 by H.C. Verma This is one of my favorite Physics book for class 9. Most of the book is within the limits of CBSE syllabus. It might overwhelm you with its language but I feel if you can understand the content is authentic with plenty of problems to solve.

You can use above books for extra knowledge and practicing different questions.







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