Tea Bag Model: Diffusion in the Cell

Have you ever noticed the color change of water when you put a tea bag into water? This is diffusion, which describes the movement that molecules from an area of high concentration (inside the tea bag) to an area of low concentration (in the water).

And in lives, this movement also happens. If we consider the tea bag as a cell, we can notice that they have a similar structure--some substances covered by a membrane. In fact, diffusion happens between cells and the surrounding substances every moment.

In this lab, you will use a tea bag as a model of a cell to explore how diffusion happens.

1) 2 tea bags (any kind of tea)

2) 2 beakers (greater than or equal to 200ml)

3) A kettle (to heat water)

4) Cold water (room temperature)

5) Thermometer

6) Timer

7) paper towel

Place the two beakers on the table and mark "hot" and "cold" on the beaker respectively.

Put 200 mL of water in each beaker. Hot water should be approximately 60 degrees, and cold water should be approximately 20 degrees.

Put tea bags in each beaker at same time and set a timer.

Observe how the tea's color spreads through the water and record the results every minute.

Compare how fast diffusion happens in the Hot water color and the Cold water color.

Throw tea bags and clean up the beaker, use a paper towel to wipe the table. Put all materials back.

This experiment shows how substances move across the membrane and the impact of temperature.

The tea bag represents the cell, and the tea bag filter acts as a cell membrane. It allows the small particles (tea particles) pass through but not the cell content (leaves). The tea inside the bag represents the inside of the cell, which has the higher concentration of molecules. The water outsaid the bag represents the environment around the cell, which has the lower concentration of molecules. In diffusion, molecules move from the higher concentration side (inside the tea bag) to the lower concentration side (outside the tea bag).

In hot water, diffusion happens faster because the molecules move faster. In cold water, diffusion happens slower because the molecules move slower.

This is very similar to cell diffusion.

1) How does the molecules move through the tea bag?

2) What type of substances move through the tea bag, and what type of substances can't across the tea bag?

3) In which cup did diffusion happen faster? Why?

4) Why is diffusion important to living things? What might happens if diffusion does not exist?

5) Are there any real world application of diffusion? Please list 3 of them.