Grade Level: 9th - 12th; Type: Life Science
Osmosis and diffusion are in some ways alike. This experiment will be covering diffusion. The sodium hydroxide will mix with the phenolphthalein agar cubes and diffuse into the cubes. You will be able to see how much diffusion had occurred and compare the ratios of surface areas to volumes. You will then conclude which is better for diffusion and cell absorbing, more surface area, or more volume.
- In which cube was diffusion the most present?
- Does the ratio of surface area to volume have to do with anything?
- Why did the sodium hydroxide change colors?
Diffusion is the mixing of a substance with another substance in order to create equilibrium of both substances. The solution will try to diffuse through the agar cube. You will then see if more surface area has any effect to the rate of diffusion. Let’s get this project started shall we! Do not forget to put on your goggles and gloves!
- Block of phenolphthalein agar
- 100 ml 4% sodium hydroxide
- Plastic spoon
- Beaker 250mL
- plastic table knife
- millimeter ruler
- paper towel
- Cut the agar cube into 3 smaller cubes. One 3cm, one 2cm, and one 1cm.
- Calculate their surface area to volume ratios.
- Put the 3 cubes into the beaker and fill the beaker ¾ full with sodium hydroxide. The colors should change.
- Leave it in there for 10 - 15 minutes.
- Take them out and dry each of them.
- Slice all of them in half and measure the amount of diffusion present in the cube by using the millimeter ruler and measuring the distance from the edge of the cube to the white part of the cube.
- Record all your data. Make a conclusion.
Terms/Concepts: Diffusion; Mixtures; Osmosis; Chemical Reactions
Sodium Hydroxide – http://www.wisegeek.com/what-is-sodium-hydroxide.htm
Phenolphthalein – http://digipac.ca/chemical/equilibrium/phenolpthalein.htm