OSMOSIS: Flashcards
What is a calibration curve?
= graph used to find an unknown concentration compared to a set of samples of known concentration
What is a dilution series?
= to make a collection of samples with known concentrations
= progressivley get more dilute by adding more water
What is the first step of the practical?
= make a dilution serires of 1m sucrose solution
= make a concentration of 0,0,2,0.4,0.6,0.8, and 1M solutuion
= make up with distilled water
= make 20cm^3 of each solution
How do we calculate a dilution factor?
= divide old concentratioj by the desired
= and divide total volume by dilution factor
What is the second step?
= use a cork borer, to cut 6 identical sized chips from the potato- identical size, blot to remove excess water- dont want to rub too dry
= weigh each potato- to calculate percentage change of mass-
= place one chip in each solution and measure the mass change mass/original mass x 100
=
How do we produce the calibration curve?
= plot graph as change in mass against toncentration of sucrose solution made
Where there is an intersection what does this mean?
= solution is isotonic
= equalibrian is reached
= no net movement of water
= water potential of the sucrose is the same as the potato tissue
What is the risk of broken glass?
= cuts-sharp
= take care when handling and keep away from the edge
What is the risk of the scalpel?
= cuts sharp
= use forceps to stabalise potato when cutting, keep away from edge cut away frokm body
What happens to potato in lower sucrose solution?
= lower sucrose potential means higher water potential, water moves into the potato by osmosis, from high to low so an increase in mass
What happens when the potato is in a higher solute concentration?
solution: high solute, low water potential to the potato, water moves out the potato into the solution, loss of mass
How do we make a dilution series?
= 100% stock solution
= 1 part stock solution- 9 parts water-10%
= 1 part fo 10% 9 parts water- 1% concentration
= 1 part 1% solution 9 parts water, 0.1 concentrationWhat
What are the advantages of a dilution series?
= enables you to make solutions with low concentrations, without having to measure small volumes- so improves accuracy
What are the 2 equations?
= c1 x v1 = c2 x v2
= c1: concentation of stock solution
= v1: volume of stock solution trasfer
=c2: concenrationof bolume making
v2: volume of solutuion you are making
v2= v1 + volume of distilled water to dilute with
