Lab: Diffusion and Osmosis

SBI3C Lab: Diffusion and Osmosis

PART A: DIFFUSION

Diffusion is the movement of molecules through a selectively permeable membrane from an area of high concentration (lots of molecules) to an area of low concentration (not a lot of molecules). This is so there will be equal number of molecules on both sides of the membrane.

Selectively permeable membranes are those that have openings called pores. Pores let water, oxygen, carbon dioxide and other specific small molecules go through the membrane.

Brewing tea and making coffee involves the diffusion of tea or coffee molecules into water.

Procedure:

1. Place 200 mL of hot water, room temperature water (warm to the touch) and cold water into 3 separate beakers.

2. Gently place a tea bag on the surface of the water in each beaker at the same time. Do not disturb/move this tea bag.

3. Observe the diffusion process in each beaker and record it in the table below.

Observations:

Tea bag in HOT water Tea bag in WARM water Tea bag in COLD water

Questions:

1. Does the filter paper of the teabag act as a selectively permeable membrane? Explain. 2. How did the temperature of the water affect the diffusion of tea molecules in each of the three beakers?

PART B: OSMOSIS

Osmosis is the diffusion of water molecules across a selectively permeable membrane. This means that water can go through membranes from areas where there are a lot of water molecules to areas where there are not so many water molecules.

Observations:

Day 1 – Raw Egg

Day 2 – Egg soaked in vinegar Draw a diagram of the egg in the beaker. Use arrows to show the movement of particles.

Day 3 – Egg soaked in corn syrup Draw a diagram of the egg in the beaker. Use arrows to show the movement of particles.

Day 4 – Egg soaked in water Draw a diagram of the egg in the beaker. Use arrows to show the movement of particles. Questions:

1. When the egg was placed in the water, which direction did the water molecules move? Explain your answer.

2. Why do grocery stores spray their fresh produce with water?

3. If a shipwrecked crew drank salt water, they could die. Explain why.

4. If you sprinkle a vegetable such as zucchini or eggplant with salt, a few minutes later, they will be covered with juice. Explain why this happens.