How to prove the existence of pinhole edge effect
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Principle
Stomata transpiration is the main way for plants to lose water. The stomata are very small, and their total area generally does not exceed 1% of the leaf area. %, such an amazing amount of transpiration can be explained by the principle of small hole diffusion. The amount of moisture diffusing through the pores is proportional to the peripheral length of the pores, but not proportional to the pore area. The phenomenon produced by this test can prove the existence of the hole edge effect.
1. The way substances diffuse through pores
Prepare a piece of polyethylene plastic film (a food bag can be used), about 5×5cm in size, take a dissecting needle and heat it on a gas lamp, and puncture a small hole in the center of the film. Prepare 1% agar and pour it into a small beaker, such as a 10ml small beaker, it is easier to observe. When the agar is not completely solidified, carefully stick the film on the surface of the agar so that the small hole is in the center of the beaker. After the agar has solidified, pour a little of the colored solution on top of the film. After 4 to 5 hours, the colored solution can be seen to diffuse into the agar gel through the pores, forming a colored hemisphere, which shows the way the dye diffuses through the pores.Glass Beakers Clear,Graduated Beaker,Science Beaker
2. Cut the cardstock into a circle that is the same size as the petri dish, and then cut a large square hole in a piece of cardstock, each side is 3cm long, and the area is 9cm². Cut several small holes in another cardstock, the total area of which is exactly the same as the large holes. To do this, cut it into 9 square holes with a length of 1 cm on each side, and distribute them evenly on the circular cardstock, then immerse the cardstock in melted paraffin, take it out and cover it on a petri dish, And seal the edges with paraffin. Add the same amount of sprinkling essence (or acetone) to each of the two petri dishes, and place the petri dishes on both sides of the flat to adjust the balance with alcohol. After 15-30 minutes, due to the high edge effect, the alcohol evaporates faster, so the pointer of the balance is inclined to the side of the large hole. It can be seen that although the total area of the hole is the same, the alcohol loss ratio through the small hole is large. Holes are much faster. It is proved that the edge effect of small holes is larger because the peripheral length is larger than that of large holes.
Post time: Jan-26-2022
