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Osmosis is the movement of water molecules through a selectively-permeable membrane, from a region of (i) **higher** concentration of water molecules to a region of (ii) **lower** concentration of water molecules - Leaving Cert Biology - Question 9 - 2017
Question 9
Osmosis is the movement of water molecules through a selectively-permeable membrane, from a region of (i) **higher** concentration of water molecules to a region of ... show full transcript
Worked Solution & Example Answer:Osmosis is the movement of water molecules through a selectively-permeable membrane, from a region of (i) **higher** concentration of water molecules to a region of (ii) **lower** concentration of water molecules - Leaving Cert Biology - Question 9 - 2017
Step 1
Step 2
In the space below, draw a labelled diagram of the apparatus you used in your demonstration.
Answer
To demonstrate osmosis, I used a setup consisting of two solutions (sugar solution and water) and a semi-permeable membrane, such as a potato or visking tubing. The labelled diagram should show:
- Two beakers or containers (one with sugar solution and one with water).
- A semi-permeable membrane separating the two solutions.
- Arrows indicating the movement of water from the beaker with higher water concentration to the one with lower water concentration.
Step 3
Suggest a control that you might use in this activity.
Answer
A suitable control might be to use another piece of tubing or a potato that is placed in the same solutions but without any sugar added to one of the beakers. This ensures that any change observed is due to the concentration gradient created by the sugar solution.
Step 4
State the result(s) of the demonstration.
Answer
The results of the demonstration would typically show that the tubing becomes lighter or swells when placed in the sugar solution due to water moving into it from the surrounding solution, or that water level changes in the beakers based on the movement of molecules.
Step 5
Briefly explain the result(s).
Answer
The results can be explained by the principle of osmosis, where water moves from an area of higher concentration of water molecules (the distilled water) to an area of lower concentration of water molecules (the sugar solution) across the semi-permeable membrane. This process continues until equilibrium is reached.
Step 6
Suggest how storing food in salty water prevents the growth of bacteria or fungi.
Answer
Storing food in salty water creates a hypertonic environment; microorganisms such as bacteria or fungi lose water through osmosis and become dehydrated, inhibiting their growth and preserving the food.