Bio- Osmosis (in Potatoes) practical Flashcards
(9 cards)
What is the Osmosis practical trying to investigate?
This practical is trying to investigate the effect of a range of concentrations of sugar solution on the mass of plant tissue (eg potatoes).
What are independent, dependent, and control variable in this experiment?
Independent- Concentration of Sugar + the size of the potatoes
Dependent- Weight of the Potato
Control- Same volume of sugar solution, + blotting off excess for each one
What Apparatus is needed?
Apparatus:
-Potato
-Cork borer
-Ruler
-Balance
-10cm³ measuring cylinder or syringe
-Labels
-Boiling tubes
-Test Tube rack
-Paper Towels
-Knife
-White tile
-Sugar Solutions
What is the Method for this experiment?
1) Use a cork borer to cut potato cylinders of the same diameter
2) Trim the cylinders to the same approximate length, using ruler
3) Measure out 10cm ³ of the first sugar solution and place this is in a labeled boiling tube
4) Weigh one of your potato cylinders + add this to the tube
5) Repeat the steps above for each sugar concentration
6) Leave the potatoes in the tube for 15 minutes
7) Plan and draw your results table
8) Remove the cylinders from the tubes carefully after 15 mins
DO NOT MUDDLE THEM UP
9) Carefully blot them dry with a paper towel
10) Reweigh the mass of each potato cylinder
11) Record all the data in the results table
12) Calculate change in mass for each concentration and plot your results on a graph.
What is the equation for calculating change in mass?
Final mass - Initial Mass
——————————— x 100
Initial Mass
Explain what happened in terms of Osmosis.
When the concentration of Sucrose was low in the solutions, they had more water and so, following the concentration gradient, travelled an abundant place to a low place - inside the potato, making it gain weight because of the water.
At 0.4, it was Isotonic, meaning that the concentration of water was the same, in and out of the potato, so it should not change weight.
When the sucrose concentrations got higher, there was less water and so the water travelled out of the potato, making it lose weight.
Why did we keep the volume of potatoes the same for each experiment?
We kept the volume of the potatoes the same for each potato to be able to compare with each other + to get accurate results.
Why did we blot the potatoes dry, after the 15 minutes in the sugar solutions?
To ensure that we weren’t weighing excess water, which could affect our results.
Why do we calculate the percentage change in mass?
We calculate the percentage change in mass as, though the potatoes are the same size, they weren’t all the same weight, so this is to ensure an average overall accuracy.
