Required Practical 3 Flashcards
each potato core should be put in a sucrose solution for approximately 24 hours
why
- to obtain large change in density / conc
- so equilibrium reached
you covered potato cores with a moist paper towel until they were needed
why
- prevent evaporation
- loss of water from cells would change initial WP
explain why an increase in density would occur
- WP lower in potato
- water enters potato by osmosis
- loss of water from surrounding solution increases density
you used changes in density to find the water potential of the potato tissue
give limitations of this method that could make your results / conc unreliable
- temp not constant
- variation in WP of cells
- dye gradually dispenses in sol
- drops of different sizes move at diff speeds
- drop moves too quickly to measure distance / time accurately
in this investigation, you were given potato cylinders taken from potatoes of the same variety
give one reason why this was important
have same WP
potato skin had been removed from the cylinders given to you
suggest why the potato skin could have affected osmosis
- skin impermeable to water
- skin is different tissue
- CELLS of skin have diff WP
in this investigation, you should have used potato cylinders that were all the same length
why
- same surface area
- which affects rate of uptake of water
describe how you would use your results for 100% blackcurrant squash to find the rate of osmosis
- find difference in mass
- divide by time
explain why the percentage change in mass of potato cylinders would be the dame between 2 sol
no further loss of water
