Over the last 500 years humans have gone from seeing a man in the moon to seeing a man on the moon. This phenomenal advance in collective learning has taken place thanks in large part to a group of strategies which have come to be referred to as The Scientific Method. If humankind has made so much progress by using the Scientific Method, then why not teach all our children to use it at an early age rather than waiting until high school or college to teach a few who are fast-tracked into science and technology careers. If we have made this much progress with a few humans using these strategies, then what will our collective learning curve look like if we are all trained to make science discoveries and/or to appreciate the discoveries of others?

Wednesday, March 5, 2008

Osmosis Conclusions

SWBAT explain a natual phenomenom by applying a scientific concept.
Why did the potato in salt water shrink?

OPENING:

Display the definition of OSMOSIS and SEMIPERMEABLE MEMBRANE

Diffusion of water across a semipermeable membrane.

Movement of water from area of low solute concentration to an area of high solute concentration until dynamic equilibrium is achieved. Favors dilution.

Osmosis is the diffusion of water through a cell wall or membrane or any semi-permeable barrier from a solution of low solute concentration to a solution with high solute concentration, up a solute concentration gradient. It is a physical process in which a solvent moves, without input of energy, across a semi-permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations.

Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

semipermeable membrane - a membrane (as a cell membrane) that allows some molecules to pass through but not others

Give students the Pattern:

1. Define: Osmosis means the movement of water from a region of high water concentration through a semi-permeable membane to a region of low water concentration.

2. Draw: Display a drawing that models Osmosis.

3. Explain: The cells in the potato shrank because the water flowed out of the potato, which had an area of high concentration of water to the water in the (beaker) (petri dish) which had an area of low water concentration.

The salt solution dehydrates the potato slice by osmosis --
water inside the potato cells diffuses out in an attempt to dilute the
salt solution. Osmotic flow always occurs in the direction that favors
dilution. Rather than the salt entering the cells, water inside flows out
into the salt solution.

GROUP WORK

Apply: Why would you die of thirst if you drank sea water?

Helpful questions for those who get stuck: Where does the water go after you drink it? Stomach, Small Intestine, Large Intestine, Blood Stream.

If the water in the blood is saltier than the water in the cells, what will happen to the water in the cells? Water will diffuse out of the cells into the blood stream. Cells will become dehydrated.


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HOMEWORK:

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