Name_____________________
Block_____________________
Surface Area to Volume Ratio Investigation
Materials:
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Agar blocks
Container of household ammonia (Enough to cover the agar blocks in the
containers)
1 Labquest
2 temperature probes
250 mL beaker
50 mL beaker
½ of petri dish
100 mL graduated cylinder
Part 1
1. Create a data table that includes labels for surface area, volume, surface area to
volume ratio (SA/V), time, distance ammonia traveled, and volume of cube
unaffected by ammonia. (This should be placed in a Google doc along with your
graph for part 2 and shared with me in your IB Biology Folder!)
2. Obtain and cut three blocks of agar from your instructor, making sure each block
is a different sized cube.
3. Measure and calculate the surface area and volume of each cube and record this
in your data table
4. Place blocks into household ammonia; let sit for 5-10 minutes
5. Remove blocks and rinse with water, then cut each block in half.
6. Measure the volume inside of the cube that was not affected by ammonia. If the
ammonia diffused all the way through the block, then the volume receiving no
diffused particles would be 0.00 cm3
Observations
1. Describe what the ammonia used in the lab represents in the cell.
2. As the size of the cell increases, which increases faster: cell surface area or cell
volume? Explain.
3.
As cell size increases, describe what happens to the surface area to volume ratio.
4. Based on your understanding of cell size and the rate (speed) of diffusion, explain why
there are generally no extremely large cells.
5. Give an example of a cell that is designed to maximize the surface area to volume ratio
and explain how the design benefits that type of cell.
Part 2
1. Obtain the bottom portion of a petri dish and a 50 mL beaker.
2. Using the hot plate, heat up 100 mL of water to near boiling.
3. Pour 30mL of the hot water into the petri dish and 30 mL into the 50 mL beaker.
4. Using the lab quest and two separate temperature probes, place one
temperature probe into each container of water and measure the temperature of
the water for 10 minutes. Make sure that the Labquest is set to take a
temperature reading once every minute for ten minutes (you should end up with
10 total data points).
5. Create a graph of your data by exporting the data into logger pro on your
computer. Export this graph into your lab document by taking a screen shot and
inserting the image.
Observations
1. Calculate the total percent loss of temperature for both the beaker and the petri
dish. Make sure to show your work.
2. State which container lost the most heat and explain why this occurred.
3. Suggest how this demonstration could apply to living organisms and their ability
to maintain body heat.