What evidence did we have that diffusion was happening in the agar cubes?
There is evidence that something diffused out of the agar since the clear sodium hydroxide solution into which the agar cubes were placed turned purple from the phenolphthalein diffusing out of the agar cube.
What do the agar cubes represent in this lab?
The agar cubes represent biological cells. The volume of the cube correlates to the cytoplasm and the surface area of each cube to the cell membrane. All living cells are dependent on diffusion processes for survival. These processes transport materials across the cell membrane into and out of the cell.
How can you determine the rate of diffusion in the agar cubes?
Calculating % diffusion in each cube:
- Calculate total volume of each cube (volume = L x W x H)
- Calculate volume that did not turn pink.
- Calculate volume diffused = total volume – volume not pink.
- Calculate % diffusion = Volume diffused /total volume x 100.
What is actually diffusing into the agar blocks?
Diffusion occurs when molecules in an area of higher concentration move to an area of lower concentration. As hydrogen ions from the vinegar move into the agar cube, the color of the cube changes allowing you to see how far they have diffused.
Why did the acid diffuse across all sides of the cubes equally?
It lacks a semi-permeable membrane and only allows for simple diffusion unlike real-life membranes. This would ensure that diffusion could occur evenly through all the sides of the cube.
How does this activity model diffusion of substances into cells?
How does this activity model diffusion of substances into cells? This activity models diffusion of substances into cells because the agar cubes represent cells and the phenolphthalein represents a substance that is diffusing across the cell membrane (outside of the cube).
How does cell shape affect diffusion?
What is the relationship between cell size and diffusion? The surface-to-volume ratio of a sphere is 3/r; as the cell gets bigger, its surface-to-volume ratio decreases, making diffusion less efficient. The larger the size of the sphere, or animal, the less surface area for diffusion it possesses.
How do you make an agar cube for diffusion lab?
Agar Cubes (Preparation)
- Prepare a 2% solution of agar. Mix 20 g of agar with 1 L of distilled water.
- Heat almost to a boil. Stir frequently until solution is clear.
- Remove from heat and add 10 mL of 1% phenolphthalein solution.
- Pour agar into a shallow tray to a depth of 3 cm and allow it to set (over night).
What is the relationship of the size of the cubes to diffusion?
In other words, if the cube dimensions are doubled, the time it takes for the hydrogen ions to completely diffuse in more than doubles. When you triple the size, the time to diffuse MUCH more than triples.
Why did the acid diffuse into the agar?
How does Acid affect diffusion?
The action of diffusion was tested by concentration of different hydrochloric acids in an experiment where more diffusion occurred as the acids got higher in concentration. The reaction to the acids increased as the concentration of the acids increased meaning more diffusion.