Physical Chemistry 2.pdf - OER@AVU - African Virtual University

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Learning activity # 2 Title of Learning Activity: Colloids On completion of this Unit, the learner should be able to: African Virtual University • Describe the properties of colloidal systems • Differentiate the different types of colloidal systems • Explain factors affecting the stability of colloidal systems • Describe and explain the properties of colloids such diffusion, osmosis, viscosity and electrical properties of colloidal systems Summary of the learning activity This learning activity is about colloids and their properties. By definition these are solutions with particles in a particular size range and exhibit characteristic properties. The colloidal system is a homogeneous system comprising a disperse phase in the range 50 -2000 Å in a continuous phase. Colloids are found in many natural and synthetic products and have their own peculiar properties. These properties are related primarily to the particle size and surface. In this activity, the learner is introduced to colloidal systems, the types of colloids and how such colloidal systems are prepared. Since colloidal systems are in part defined based on size it is important that the size of the disperse phase be maintained within the colloidal range. Hence, factors that affect colloidal stability are also examined. The unique properties of colloids, such as electrical and surface properties are discussed. Colloids are particularly significant to the study of surface phenomenon because their surface area-to-volume ratio is very large. Consequently, their properties are dominated by events at their surface. List of REQUIRED readings • Colloids • Interfaces, Colloids And Gels List of relevant useful links Experiments On Surface Phenomena And Colloids http://www.funscience.com Colloids http://ull.chemistry.uakron.edu/genobc/Chapter_07/
List of relevant MULTIMEDIA resources African Virtual University • Computer with internet connectivity to enable access to open source learning materials and interactive learning through email, video conferencing and use of CD-ROMs • QuickTime Movie Player Software • Shockwave Player Software • Macromedia Flash Player Software Detailed description of the activity The study of colloids starts by establishing the nature of colloids and the different types of colloidal systems that exists: lyophilic and lyophobic. The basic method used to produce colloidal systems is discussed followed by factors that affect their stability. You will also learn how such systems can be stabilised to maintain colloidal characteristics and properties. Properties associated with colloids such as Brownian motion, diffusion, osmotic pressure and viscosity will be studied. The effect of adsorption of charged species onto colloid particle surfaces is covered. Formative evaluation • As you make your way through this learning activity you will come across problems to test your conceptual understanding of the subject matter • Rapid quizzes are provided to check your understanding • Practical experiments will be given to evaluate your understanding of theorypractice relations • Simulated experiments/exercise will given to test your understanding of certain concepts Learning activities Colloids are a class of materials found in a wide range of products from cosmetics, food, paints to pharmaceuticals. The substances include solids, emulsified liquids, clays, gels and proteins. The colloid system consists of small particles dispersed in a continuous phase. Although they are aggregates of atoms or molecules, colloidal particles are not ordinarily seen by an optical microscope. It should however be noted that the size limits are somewhat arbitrary and some systems may contain particles that are outside the size range. The extensive interface created between the particles and disperse phase is a predominant feature of colloidal systems. The surface area is so much larger than an equal volume of particles. For example, colloidal platinum is an effective catalyst, which is achieved by absorbing the reactants to its surface. The colour of a colloidal system is affected or related to the size of particles. Gold for example gives a red colour in a sol form but turns blue as the size increases.
Page 1 and 2: Physical Chemistry 2 Prepared by On
Page 3 and 4: Table of ConTenTs African Virtual U
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Page 7 and 8: Unit IV Electrochemistry (20 hours)
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Page 17 and 18: List of required readings • Solut
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Page 21 and 22: Practice problem 1 Which of the fol
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Page 25 and 26: Visual demonstration: Forces of coh
Page 27 and 28: Simulation: Solution of salt 1.4 Th
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Page 73 and 74: Practice problem 1 What is X in the
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Reading #3 COLLOIDS African Virtual
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Reading # 9 INTRODUCTION TO RADIOAC
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African Virtual University Rational
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Useful Link #2 Title : Chem1 Virtua
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Useful Link # 5 Title : Chemistry U
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Useful Link # 8 Title : Chemistry R
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Useful Link # 11 Title : RAdiation
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XVI. summative evaluation African V
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(c) 0.09V (d) -0.09V African Virtua
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XVII. References African Virtual Un
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Physical Chemistry 2.pdf - OER@AVU - African Virtual University

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