Mr Reece May

Topics: Iodine, Concentration, Semipermeable membrane Pages: 3 (845 words) Published: May 9, 2013
Aim: To observe and describe an example of osmosis.
Hypothesis: I predict that the water level will rise as the iodine stained water moves through the cellulose bag due to osmosis. The iodine is there so we can see this happening. Materials:
* Dialysis(cellulose) tubing
* Thistle funnel
* Gas jar
* Retort clamp and stand
* Rubber bands
* 50mL beaker
* Iodine/potassium iodine solution
* 5% starch solution
1) Fill the gas jar to 3 quarters full with water. Add iodine solution until the water is quite yellow/brown. 2) Moisten the cellulose tubing and tie a knot at 1 end. At the other end insert the stem of the thistle funnel & fasten it firmly with a rubber band. 3) Fill the cellulose tubing with starch solution until it rises 2-3cm up the stem of the funnel. Dislodge any air bubbles & thoroughly rinse both the funnel stem * the bag under running water to remove any traces of starch from the outside. 4) Accurately mark the level of the starch solution on the funnel stem with a marking pen. 5) Use the retort stand & clamp to suspend the tubing in the glass jar containing the iodine & water (figure 1.19). 6) Leave the set up standing undisturbed for at least 20 mins. Results: Well after we had done all of the method we found that indeed my hypothesis was correct, the water level in the thistle funnel had raised 1 and a half cm. The cellulose bag had also turned black/blue due to the iodine that entered the cellulose bag along with the water which was all due to osmosis (figure 1.20) – (figure 1.21) Discussion: Well the results defiantly supported my hypothesis, which led me to believe that water could pass through the cellulose bag due to osmosis, which is the movement of free water molecules through a partially permeable membrane, moving from a dilute to a concentrated solution ( the starch solution was more concentrated than the water). This is a very good example of osmosis because you...
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