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Reason
Osmosis is the passage of water molecules from a region of high water concentration, through a semi-permeable membrane to a region of low water concentration.
Sucrose solution contains less water molecules (more dilute) than the chip so the water molecules will pass into the sucrose solution therefore making the mass of the chip less. Dilute water contains more water molecules (more concentrated) than the chip so the water molecules from the dilute water will pass into the chip therefore making the mass of the chip more.
The more sucrose solution added to distilled water the more dilute the solution becomes. Therefore the more sucrose solution added the smaller the mass of the chip becomes. The more distilled water added the more concentrated the solution becomes. Therefore the more distilled water added the bigger the mass of the hip becomes.
Below is a diagram to explain osmosis.
Dilute Solution Concentrated solution
Semi-Permeable membrane
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Pre-experiment
From the results that I got from my pre-experiment I have decided to measure my official tests over a 1 hour period. This is because that was where the biggest change occurs. At 24 hours the changes start to decrease.
I have come across the problem that I cannot measure for one hour because I need 10 minutes at the beginning of each lesson to get my equipment set up. Due to this I am going to measure the changes in mass of the chips over 50 minutes. I will do this three times to get good, accurate results.
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Method
- Collect up all the equipment and set up five test tubes.
- Then fill the first test tube up with 20ml of sucrose solution. Fill the second test tube up with 15ml of sucrose solution and 5ml of Distilled water. Fill the third test tube with 10ml of each sucrose solution and distilled water. Fill the forth test tube with 5ml of sucrose solution and 15ml of distilled water. Finally fill the fifth test tube with 20ml of distilled water.
- Next cut the chips into five 2cm long pieces.
- Then measure the weight of each piece of chip.
- Next drop each piece of chip into each of the five test tubes
- Then start the timer for fifty minutes.
- When the timer reaches 50 minutes take each piece of chip out and dab them dry.
- Finally re-weigh the pieces of chip and recorded there change.
Things I did to make it a fair test
To make the experiment a fair test I made sure that all the chips were left in the test tubes for the same amount of time. I also made sure that I measured the amounts of sucrose solution and distilled water accurately. I kept the amounts of solutions the same for all three tests. I used different solutions and test tubes for each test I did.
I am keeping the amount of solutions constant through out all thee tests. Each test tube will be filled with 20ml of different mixtures of distilled water and sucrose solution.
I could not get the mass of the chips exactly the same as each other so I cut them all at a length of 2cm to get them all approximately the same mass.
I am going to repeat my experiment three times to get accurate results.
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Equipment list
- 20 test tubes (concluding the three repeats)
- 20 2cm long potato chips
- Sucrose solution
- Distilled water
- Accurate scales
- Stop watch
- Razor blade
- Measuring cylinder
- Paper towel
Safety
To make my experiment safer I made sure I handles each test tube carefully so I did not smash them. Before I started my experiment I made sure my bags were well out of the way so that I did not trip over them while carrying out my experiment. I made sure I washed my hands thoroughly after I had finished my experiment. I made sure I did not rush when putting away my apparatus because this is how accidents can be caused. I did not carry out my experiment until I knew there was a teacher present in the lab. I made sure I followed the laboratory regulations while conducting my experiment.
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