Lab Manual - eScience Labs

Lab 5: Chemistry of Life
mediately stop the microwave, but leave the soluon inside for two minutes to cool down.
2. Aer 30 seconds in the microwave, remove the bole with a hot pad. Screw the lid back onto
the bole and swirl the soluon. If the soluon is not completely liquefied, remove the lid
and place the agar bole into the microwave for 10 second intervals, swirling in between, un-
l it is completely liquefied. Aer it is liquefied, let the soluon sit for a minute to cool down.
3. Once the agar soluon has cooled slightly, measure 40ml into a beaker.
4. Add 10ml of the bromothymol blue soluon to the liquefied agar in the beaker. Finally, add 2
ml sodium bicarbonate to the beaker soluon. Pipee the soluon up and down to mix. This
should nt the mixture and allow you to observe a pH change that will occur in subsequent
steps.
5. Once the soluon is mixed, pour the beaker soluon into the rectangular mold. Cover the
container with plasc wrap and let sit for 24 hours to solidify.
Note: Be sure to wash any labware that was used for the agar immediately to avoid it solidifying in
your equipment!
Procedure
1. First, put on safety gloves, safety glasses and apron for safety. Then, check to be sure the agar
has solidified. If it has not, let it sit for another 12 hours.
2. Begin by inverng the rectangular mold, leng the agar block fall onto the underpad (you may
have to run a knife around the edges to loosen it).
3. From this block, safely cut out a 1cm x 1cm x 6cm cube. Note: Be sure to measure out the 6cm
first as to avoid any errors.
4. From the remaining agar, safely cut out a 1cm x 1cm x 1cm block. Set the block aside.
5. From the remaining agar, safely cut out a 2cm x 2cm x 2cm block. Set this block with the others.
6. Once all three blocks have been cut, dispose of the scraps of remaining agar. Do not dispose of
the blocks you just cut.
7. Then, measure the surface area, volume and surface area to volume rao for each cube. Write
those in Table 2.
8. Fill the cleaned 250mL beaker with 150mL of vinegar. Gently place all three blocks into the
vinegar soluon.
9. Observe as the blocks begin to change colors. Let them sit in the vinegar for 7 minutes.
10. Aer 7 minutes, remove the blocks from the vinegar soluon. Pour the remaining vinegar soluon
down the drain.
11. Gently blot the cubes dry and then safely cut the cubes in half. For each cube, measure the
distance the vinegar diffused into the gelan cube, as detected by the color change. Do this by
measuring from the outer edge of the cube to the blue rim inside the cube. Record that value
in Table 2.
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