Science Presentation: Diffusion and Osmosis

1. Science Presentation: Diffusion and Osmosis Done By: Gordon Koh Qian Siang (15) Keven Loo Yuquan (14) Lam Wen Hong (16) Alex Liew Zhi Jie (17) http://en.wikipedia.org/wiki/Diffusion

2. Question 2 If you scatter salt on the soil of a potted plant, the plant may shrivel up and die. Why?

3. Salt • A salty environment creates a concentration gradient in which water is pulled out. • E.g. Soaking of ham in salt. Soaking the ham in a concentrated salt-water solution will draw out any excess water in the meat. • Water will flow from areas of high water concentration (in the ham) to an area of low water concentration (in the salt-water solution).

4. Salt on soil Applying the same logic: • When the salt is scattered on the plant, it absorbs moisture in the soil, thus dehydrating the plant. • Plant has a lack of water. • Plant dies eventually.

5. Question 3 Although diffusion plays an important role in the transport of substances in living things, it is not the only means of transport, especially in large organisms such as human beings. Suggest why diffusion alone is not an efficient means of transport of substances in large organisms.

6. Definition Diffusion is: the spread of particles through random motion from regions of higher concentration to regions of lower concentration over a period of time. the particles will eventually result in a uniform concentration throughout the mix Diffusion can still occur when there is no concentration gradient (but there will be no net flux).

7. Molecular Diffusion In molecular diffusion, the moving entities are small molecules. the molecules move at random because they frequently collide. diffusion is this thermal motion of all (liquid and gas) molecules at temperatures above absolute zero. diffusion rate is a function of only temperature, and is not affected by concentration. Brownian motion is observed in molecules that are so large that they are not driven by their own thermal energy but by collisions with solvent particles.

8. Diffusion in the human body [1] This is one example of diffusion in the human body: Diffusion takes place in the alveoli. Due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out. Also, the lungs are adapted for diffusion as there are many alveoli, increasing surface area for faster diffusion.

9. Diffusion in the human body [2] Incomplete slide There is another example of diffusion in the human body: [insert example]

10. Inefficient Diffusion Our suggested reason why diffusion is inefficient: Diffusion is slow It is the basic way in which all nutrients, gases and wastes move in the body unless active transport is required which uses protein carriers instead in place where either diffusion is not possible because of the nature of substance or because it has to be transported to an area with an already high concentration of it.  Incomplete slide

11. Bibilography Question 2: • http://www.maybenow.com/Why-does-salt-dehydrate-things-q7154931 • http://www.newton.dep.anl.gov/askasci/gen06/gen06263.htm Question 3: • http://en.wikipedia.org/wiki/Diffusion • http://answers.yahoo.com/question/index?qid=20081208142932AApMEwd • http://www.blurtit.com/q914893.html