Osmosis-Experiment

Question 1

What is osmosis?

Answer 1

Osmosis is the movement of water from an area of high water concentration to an area of low water concentration across a partially permeable membrane.

Question 2

What is meant bu the term partially permeable?

Answer 2

.It will allow some substances made of small molecules to pass through but no others made of larger molecules

Question 3

What is the experiment trying to achieve?

Answer 3

.In this experiment, you can investigate the effect of glucose solution on plant tissues, using a potato

Question 4

Why are the potato chips dried before weighing them a second time?

Answer 4

.So the mass of the excess water doesn’t affect the final mass

Question 5

What is the formula to calculate the percentage change in mass?

Answer 5

         Initial mass.         X100

Question 6

Why did you compare the percentage change in mass rather than simply the change in mass of each chip?

Answer 6

.To allow for variations in the size of chips, even though attempts were made to cut them the same size

Question 7

Why was the skin of the potato cut off?

Answer 7

.It may prevent osmosis

Question 8

Explain why plant cells do not burst when they are left in pure water?

Answer 8

.Plant cells have a cell wall which provides strength and can withstand eternal pressure

Question 9

How could the student make the practical more reliable?

Answer 9

.Observe more potato chips and calculate a mean value

Question 10

How could a student make the practical more accurate?

Answer 10

Use more intermediate concentrations within the existing range

Question 11

The student repeated the investigation using boiled pieces of carrot. The pieces of carrot did not change in mass. Suggest why?

Answer 11

The partially permeable cell membrane was damaged

Question 12

What is the independent variable?

Answer 12

.Concentration of solution

Question 13

What is a dependant variable?

Answer 13

Mass and length of potato chips

Question 14

What are the control variables?

Answer 14

Same volume of water in each tube, same type of potato, same balance, same ruler etc

Question 15

Predict what will happen in each of the following model cells and explain why?

Answer 15

1) the model cell will gain mass because water will move into the model down a water potential gradient from the 1% solution
2) the model cell will lose mass because water will move out of the model cell down a water potential gradient to the saturated sugar solution
3) there will be no change. The solution in the model cell and the surrounding solution are the same concentration so there be no net movement of water

Question 16

Write one way that the Visking tubing and sugar solution is a realistic model of a cell

Answer 16

Visking tubing is partially/selectively permeable like a cell membrane

Question 17

Write down one way that the Visking tubing and sugar solution is not a realistic model of a cell?

Answer 17

.It does not contain any organelles/cells do not jist contain sugar solution. It is not alive and the Visking tubing is not made of the same substances as real cell membranes