Osmosis- Eggs (Gloria Hernandez Scipio)

Author

Gloria E. Hernandez Scipio

Principle(s) Illustrated

Osmosis
Hypertonic/Hypotonic/Isotonic
Permeability
Density

Standards

MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways part of a cell contribute to the function.
- DCI-LS1.A: Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell
MS-LS1-7: Develop a model to describe unobservable mechanisms
MS-LS1-7: Conduct an investigation to produce data to serve as the basis for evidence that meet the goals of an investigation
DCI-PS1.B Substances react chemically in characteristic ways. In a chemical process the atoms that make up the origical substances are regrouped into difference molecules, and these new substances have different properties from those of the reactants. (MS-PS1-2), (MS-PS1-3, (MS-PS1-5)

Questioning Script

Prior knowledge & experience:

Students should have a basic understanding of the structure and function of the Cell membranes. Cell membranes are semi-permeable. They let some things in and some things out.
Density- which is more dense? Karo Syrup or distilled water? Which has more matter per unit of space?
Chemical Reactions- nothing is neither created nor destroyed, but changes form.
Hypertonic, Hypotonic, Isotonic
Diffusion

Root question:

1.) For Cell Membrane and Density: What will happen to the egg in Karo Syrup? What will happen to the egg in distilled water?

2.) For Chemical Reactions: What are the reactant and products when vinegar is poured onto the egg shell? How can you tell a chemical reaction is occurring? (bubbling, change substance, etc). Why didn't it dissolve the membrane?

Target response:

1.) In karo syrup, the egg will shrink. The egg will shrink because the karo syrup is more dense than the liquid in the egg. The karo syrup is hypertonic to the egg cell. Therefore the water from the egg diffuses through the semipermeable membrane until it reaches equilibrium with its surroundings.

In distilled water, the egg will gain mass. The egg will gain mass because the distilled water is less dense than the egg. The distilled water is Hypotonic to the egg and therefore it will go through the semipermeable membrane into the egg until is reaches equilibrium with its surroundings.

2.) You can tell a chemical reaction is occurring because there is a change in temperature, bubbles are being produced (what type of bubbles are they?). The chemical reaction that is occurring is

CaCO₃+ 2H⁺ -> Ca⁺² + H₂O +CO₂ .

So the bubbles are CO2 gas!

Common Misconceptions:

Whats moving in and whats moving out.

The bubbles made are oxygen bubbles.