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Flashcards in Required Practical 3 Deck (10)
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1
Q

What is purpose of the calibration curve ?

A

They are used to determine the concentration of an unknown sample by comparing it to set of standard values with known concentrations

2
Q

How is a 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 where the plant tissue is is tonic to the sucrose solution

3
Q

What occurs when plant tissue is placed in a hypotonic solution ?

A

Water moves out of the plant tissue by osmosis, plant tissue decreases in mass

4
Q

What are the control variables of this practical ?

A

Volume of sucrose solution
Size of potato chips
Length of time left in solution
DAB each potato disk with aper towels

5
Q

What is indicated by the x intercept of the calibration curve

A

The concentration that is isotonic to the Solution tested

Wp of plant = wp of solution

6
Q

Outline the procedure of investigating osmosis

A

Make a simple dilution of 1m sucrose to produce 5 concentrations
Add 5cm t 5 different test tubes
Cut potato into equal sized chips and weigh at the start
Make sure they are fully submerged into the sucrose solution which at a constant temperature
Room temp
Leave for 20 minutes
Take out
Use paper towel to get rid of excess water
Measure mass at regular intervals

7
Q

Why is percentage used rather than the actual change in mass

A

Potato chips may not all have the same starting mass

Allows comparison

8
Q

Why did the student use potato chips from the same potato ?

A

All cells will have the same water potential

9
Q

Why is the skin removed from the potato

A

It has a different water potential

10
Q

Why did the potato chip left in distilled water gain mass?

A

They gained mass because water moved into the cells by osmosis. The water moved from a less negative water potential to a more hypertonic negative water potential increasing the mass