Sample Sci Paper The_Effect_of_Molecular_Weight_on_the_Rate_of_Diffusion_of_Substances_-_LIBRANZA.pd

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1The Effect of Molecular Weight on the Rate of Diffusion of Substances1Alexander Ken LibranzaGroup 1 Sec. A1LMarch 6, 20121A scientific paper submitted in partial fulfillment of the requirements in GeneralBiology I laboratory under Prof. Cheryl M. Talde, 2ndsem., 2011-2012.
2ABSTRACTThe effect of molecular weight on the rate of diffusion wasassessed using two tests: the glass tube test and the agar-water gel test.In the glass tube set-up, two cotton plugs soaked in two differentsubstances (HCl and NH4OH) were inserted into the two ends of the glasstube. The substance with the lighter molecular weight value (NH4OH, M =35.0459 g/mole) diffused at a faster rate (dAve= 25.8cm), resulting in theformation of a white ring around the glass closer to the side of the heaviersubstance (HCl, M = 36.4611 g/mole; dAve= 10.8 cm). The agar-water gelset up was composed of a petri dish of agar-water gel containing threewells. Drops of potassium permanganate (KMnO4), potassium dichromate(K2Cr2O7) and methylene blue were simultaneously introduced to eachwell. Methylene blue, having the largest molecular weight, displayed thesmallest diameter (18 mm) and diffused at the slowest rate (0.3668mm/min.). Thus, the higher the molecular weight, the slower the rate ofdiffusion.INTRODUCTIONA substance in the gaseous or liquid state consists of molecules or atoms thatare independent, rapid, and random in motion. These molecules frequently collide witheach other and with the sides of the container. In a period of time, this movementresults in a uniform distribution of the molecules throughout the system. This process iscalled diffusion (Everett and Everett, 2007). Diffusion occurs naturally, with the netmovement of particles flowing from an area of high concentration to an area of lowconcentration. Net diffusion can be restated as the movement of particles along theconcentration gradient.
3According to Meyertholen (2007), there are several factors which may affect therate of diffusion of a substance. These factors include the size of the particle or themolecular weight of the substance, temperature or availability of energy in the system,difference in concentrations inside the system, diffusion distance, and if the systeminvolves a membrane or barrier, thesurface area of the barrier, and the barrier’spermeability. The greater the concentration of a substance in an area of a systementails that the frequency of particles colliding with each other is higher, causing theparticles to “push” each other at a faster rate. These collisions are due to the highmolecular velocities associated with the thermal energy“powering”the particles (Nave,2008). At a given temperature, a smaller particle is said to diffuse at a faster rate than alarger one. This is because the larger the size of a particle, a greater amount of force issaid to be required to move the particle (Meyertholen, 2007). With the same amount ofenergy, a smaller particle can be pushed faster than a larger particle. Thus, the

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Term
Fall
Professor
Prof
Tags
Molecular diffusion, Potassium permanganate

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