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2008 Examination Results
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Diffusion and osmosis in animal cells
Posted Date:
01 May 2008
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0
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Posted By: CONFIDENCE IS THE COMPANION OF SUCCESS
Member Level: Diamond Posted Date: 01 May 2008
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Using eggs for science experiments can be fun and easy. Chicken eggs from the grocery store come in standardized sizes and are fairly inexpensive. Be careful with the eggs as you experiment - if they break as you are working they will make a big mess and you will be at risk because of salmonella. Be sure to wash everything (and yourself) with warm, soapy water. You may also want to use a disinfectant. Ask for adult permission.
For some of these experiments you will need hardboiled eggs. Ask for adult permission or assistance with using the stove. Place the eggs in the bottom of a saucepan. Fill it with enough cold water to cover the eggs. Place the saucepan on a burner over high heat until the water is boiling. Once the water is boiling, set a timer for 10 minutes. After 10 minutes, remove the saucepan from the burner (be sure to turn it off!) and place the pan in the sink. Run cold water over the eggs until they are cool to touch. Put the eggs in the refrigerator. Any extra eggs that you don't use for experiments can be used for egg salad!
Materials
* 3 raw eggs
* 3 jars with lids (larger than an egg, clean jelly, olive, or pickle jars)
* white vinegar, enough to fill the 3 jars
* measuring tape (vinyl one for sewing is good)
* kitchen scale (optional)
* paper towels
Procedures
You will be pouring vinegar over the eggs in the jars to observe the
changes over the 3 day period.
* How will you find the size of each egg before experimenting? Make a chart for all the measurements you take for the three eggs.
* What other measurements do you need (for the jars, the vinegar?) Add these to your table.
* Think about how you will put the eggs in vinegar for 3 days and what observations you need to record. How often will you check the eggs? Make a chart to record your observations.
* After 72 hours, carefully pour the vinegar off the eggs. Rinse them gently with water and pour off. Keeping track of which egg is which, carefully dry them with paper towel and repeat the measurements you made before the treatment. Save the eggs for the next investigation. Make a chart to record the new measurements.
Thinking About It
Compare the appearance and measurements of the eggs before and after the acid treatment. The egg shell is made of calcium carbonate. Write a sentence describing the reaction of vinegar with calcium carbonate. What other substances contain calcium carbonate?
DIFFUSION AND OSMOSIS IN ANIMAL CELLS
How do different solutions affect an animal cell?
Do substances pass through the cell membrane?
You can make different solutions to test your three egg cells. For instance,
a 10% sugar solution could be made by adding 50 ml of corn syrup to 450 ml
of water. A salt solution can be made by adding table salt to water.
Materials
* 3 eggs from previous investigation
* 3 clean jars with lids (larger than the eggs)
* 3 liquids for testing (such as distilled water, sugar solution, salt solution)
* measuring tape
* kitchen scale (optional)
* paper towels
Procedures
You will be pouring test solutions over the eggs in the jars to observe
changes over 1 to 2 days.
* How will you find the size of each treated egg cell before experimenting? Make a chart for all the measurements you take for the three eggs.
* What other measurements do you need? Think about the solutions and the jars. Add these to your table.
* Think about what observations you need to record as the eggs sit in their "baths." How often will you check the eggs? Make a chart to record your observations.
* After 24 or 48 hours, carefully pour the liquids off the eggs. Keeping track of which egg is which, carefully dry them with paper towel and repeat the measurements you made before the treatment. Make a chart to record the new measurements. You may wish to take a photograph of your eggs.
Thinking About It
Compare the apearance and measurements of the eggs before and after the liquid treatment. Try to explain each solution's effect on the egg.
Was water passing into or out of the egg?
Are there other possibilities?
Look up the definitions of OSMOSIS and DIFFUSION.
How are these seen in your experiment?
How could you design an experiment to test different sugar solutions?
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