A quick summary of the egg lab

Arslan Aziz

SSWIMS

December 2002

What did we do?What did we do?

Test our predictions for what would Test our predictions for what would happen to an egg treated with weak acids, happen to an egg treated with weak acids, corn syrup, and distilled water.corn syrup, and distilled water.

What did we find?• The egg shell dissolves

in weak acids.• Once the shell is gone,

eggs will swell due to the influx of water.

• Water is moving from an area of greater concentration to an area of lesser concentration (Osmosis)

water

waterwater

water

water

water

waterwater

What about in corn syrup?

• The egg now sits in a solution that has a lower concentration of water than the egg itself.

• The egg then shrinks due to the outflow of water.

water

water

waterwater

waterwater

waterwaterwater water

What allows for the movement of water?

• A semi-permeable membrane• Remember: Semi-permeable membranes

are selective. Some things can move across the membrane while others cannot.

• What drives the movement?– All substances are moving towards their

respective chemical potentials.– In other words, left alone, particles will spread

out until they are evenly distributed.

A barrier like this one would be permeable to golf balls, but not tennis nor basketballs…

The egg is actually covered by a semipermeable membrane. Vinegar is too large to fit through but water passes through easily.

Involves the movement of much smaller things, like water molecules. The overall effect is the same, though: over time, there would be an equal number of particles on both sides of the barrier.

Is a special type of diffusion, where there is a barrier that only allows certain things through, like water molecules, but does not let things like salt through…

So why does this matter?

• We use semi-permeable membranes everywhere!

• Examples include:Gore-Tex (water droplets

are too big to move in,

water vapor is small

Enough to move out)

Water for everyone?

• In an effort to make more fresh water available for the growing number of people in the world, we may turn to reverse osmosis using semi-permeable membranes.

Dialysis Machines

Why does this matter in living things?

• The cells of all living things are made of semi-permeable membranes!

• Our cells are exposed to the environment.

• Ex: the cells in the lining of your lungs lose moisture through evaporation as you breath.

What about organisms that live in water?

Osmoregulation

Diffusion

• Osmosis– The diffusion of water.– Water will move from

an area of greater concentration to an area of lesser concentration.

Osmosis

Pressure

Surface Current are caused by winds.

Deep Ocean Currents are caused by temperature and salinity

El Nino

Passive transport involves creating an opening from things to move from a higher concentration to a lower concentration- they do this spontaneously, so no energy is needed…

Active transport involves “pumping” things from a lower concentration to a higher concentration: this requires energy, and special pumping structures;