- Size of beaker
- Volume of deionised water within tubing
- Volume of NaCl solution (20%)
- Materials and apparatus
- Time of submersion
- 500mL Deionised water
- 2L 20% NaCl solution
- 10 Dialysis Tubes
- 10 beakers (250mL)
- 10 petri dishes
- 10 stirring rods
- Sticky labels
- 2 measuring cylinders (200mL)
- Volumetric pipettes (50mL)
- 2 teat pipettes
- Cotton string
- Electronic balance
- Paper towels
1. The beakers and measuring cylinders were rinsed and dried to remove any cause for errors.
2. Sticky notes were used to label each beaker and petri dish with the concentration of NaCl (0%, 5%, 10%, 15%, 20%).
3. The concentration of each ...view middle of the document...
The 50mL was then deposited into each tube, twisted and double knotted with the string and placed into the correctly labelled petri dish. This was repeated 5 times for each tube.
6. The electronic balance was zeroed with the empty petri dish on top and the dialysis tubes were placed and weighed individually. Their original masses were recorded in the results table.
7. The timer was set for 10 minutes and the tubes were simultaneously placed into their corresponding NaCl solutions, ensuring they were all completely submerged.
8. In preparation for the timer to end, paper towels and were laid out next to the beakers and the petri dishes were placed in front of their corresponding solutions.
9. At the end of the 10 minutes the tubes were extracted from their respective beakers and held out for 2 seconds and placed onto the paper towels to remove any excess solution. They were then placed on the correctly labelled petri dishes to be weighed.
10. Again, the balance and was zeroed with the petri dish on top and the tubes were individually weighed. Their final masses were recorded in the results table and their percentage weight changes were calculated.
11. This method was repeated in Trial 2 to attain a second set of results for means of comparison.
Safety and Risk Assessment
In order for this practical to be successful, some precautions were taken to ensure the safety of all group members. Although the NaCl solution is not harmful to humans, it is still considered a hazard so lab coats and goggles were worn. Certain risks were posed during the practical due to the handling of apparatus. The beakers, measuring cylinders, volumetric pipettes and stirring rods were all made of glass and had the potential to break if mishandled or dropped. Close attention was paid to prevent any glassware from breaking and in the event of a cut from the glass, a teacher would be notified and first aid would be...