The students measured the mass of four of the potato sticks using an electronic balance.
The students left each potato stick in one of four different liquids for 5 hours:
• distilled water
• 0.1 mol per dm3 sodium chloride solution
• 0.5 mol per dm3 sodium chloride solution
• 1.0 mol per dm3 sodium chloride
solution.
After 5 hours they measured the mass again and calculated the change in mass.
(i) Predict which of the liquids would cause the largest decrease in mass of a potato stick.
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(ii) The students dried the potato sticks with paper towels before putting them on the
electronic balance.
Suggest why.
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(c) After the experiment the students noticed that the potato stick with the lowest mass was soft
and floppy.
Explain why the potato stick had become soft and floppy.
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(d) The students followed the same experimental procedure with boiled potato sticks and found
no overall change in mass in any of the solutions.
Suggest why the mass of the boiled potato sticks remained the same.
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Answers
Explanation:
students noticed that the potato stick with the lowest mass was soft and floppy. Explain why the potato stick had become soft and floppy. ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................
Answer:
Explanation:
1. 1.0 (mol dm–3 sodium chloride solution) ;
2.(to remove) excess / surface/AW, water/AW, on potato sticks ;
to measure the mass of the potato (stick) only ;
3.cells / potato sticks, have lost water (by osmosis) ;
from high water potential to low water potential/down water potential
gradient ;
(cells / tissue/ potato) were, plasmolysed/ flaccid ;
loss of turgor (pressure) ;
not enough pressure of water pushing on cell walls ;
4. protein denatured (when cooked) ;
cell membrane, damaged/destroyed (when cooked) ;
no osmosis will occur ;