RP03 - Investigating water potential Flashcards
1
Q
What is the purpose of calibration curves
A
They are used to determine the concentration of an unknown sample by comparing it to a set of standard values with known concentrations
2
Q
How is calibration curve used to find the concentration of plant tissue
A
- Plot a calibration curve of percentage change in mass against concentration
- Find the x intercept where the plant tissue is isotonic to the sucrose solution
3
Q
How to collect data
A
4
Q
What are some control variables in this practical
A
- Total volume of solution
- Size, shape and surface area of plant
- Blot dry to remove excess water before weighing
- Length of time in solution
- Temperature
- Regularly stir to make sure all surfaces are exposed
5
Q
Why calculate % change instead of mass?
A
- Enables comparison / shows proportional change
- As plant tissue samples had different starting masses
6
Q
Why are repeats important?
A
- Allows anomalies to be identified / ignored / effect of anomalies is reduced
- Making mean more reliable
7
Q
Why blot dry before weighing?
A
- Solution on surface will add to mass (only want to measure water taken up or lost)
- Amount of solution on cube varies (so ensure same amount of solution on outside)
8
Q
Why were potato discs left in solution for 20 minutes?
A
To allow time for osmosis until the plant tissue reaches equilibrium with its surrounding solution
